{"id":280,"date":"2023-06-14T23:30:08","date_gmt":"2023-06-15T03:30:08","guid":{"rendered":"https:\/\/opentextbooks.concordia.ca\/explorationsclone\/chapter\/8\/"},"modified":"2026-01-30T17:30:18","modified_gmt":"2026-01-30T22:30:18","slug":"8","status":"publish","type":"chapter","link":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/chapter\/8\/","title":{"raw":"Primate Evolution","rendered":"Primate Evolution"},"content":{"raw":"<div class=\"__UNKNOWN__\">\r\n<p class=\"import-Normal\">Jonathan M. G. Perry, Ph.D., Western University of Health Sciences<\/p>\r\n<p class=\"import-Normal\">Stephanie L. Canington, Ph.D., University of Pennsylvania<\/p>\r\n<p class=\"import-Normal\"><em>This chapter is a revision from \"<\/em><a class=\"rId7\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Chapter 8: Primate Evolution<\/em><\/a><em>\u201d by Jonathan M. G. Perry and Stephanie L. Canington. In <\/em><a class=\"rId8\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\"><em>Explorations: An Open Invitation to Biological Anthropology, first edition<\/em><\/a><em>, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under <\/em><a class=\"rId9\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\"><em>CC BY-NC 4.0<\/em><\/a><em>. <\/em><\/p>\r\n\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<h2 class=\"textbox__title\"><span style=\"color: #000000\">Learning Objectives<\/span><\/h2>\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ul>\r\n \t<li>Understand the major trends in primate evolution from the origin of primates to the origin of our own species.<\/li>\r\n \t<li>Learn about primate adaptations and how they characterize major primate groups.<\/li>\r\n \t<li>Discuss the kinds of evidence that anthropologists use to find out how extinct primates are related to each other and to living primates.<\/li>\r\n \t<li>Recognize how the changing geography and climate of Earth have influenced where and when primates have thrived or gone extinct.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<p class=\"import-Normal\">The first fifty million years of primate evolution was a series of <strong>[pb_glossary id=\"1683\"]adaptive radiations[\/pb_glossary]<\/strong> leading to the diversification of the earliest lemurs, monkeys, and apes. The primate story begins in the canopy and understory of conifer-dominated forests, with our small, furtive ancestors subsisting at night, beneath the notice of day-active dinosaurs.<\/p>\r\n<p class=\"import-Normal\">From the ancient [pb_glossary id=\"1684\"]<strong>plesiadapiforms<\/strong>[\/pb_glossary] (archaic primates) to the earliest groups of true primates ([pb_glossary id=\"1686\"]<strong>euprimates<\/strong>[\/pb_glossary]) (Bloch and Boyer 2002), the origin of our own order is characterized by the struggle for new food sources and microhabitats in the arboreal setting. Climate change forced major extinctions as the northern continents became increasingly dry, cold, and seasonal and as tropical rainforests gave way to deciduous forests, woodlands, and eventually grasslands. Lemurs, lorises, and tarsiers\u2014once diverse groups containing many species\u2014became rare, except for lemurs in Madagascar, where there were no anthropoid competitors and perhaps few predators. Meanwhile, <strong>[pb_glossary id=\"1685\"]anthropoids[\/pb_glossary]<\/strong> (monkeys and apes) likely emerged in Asia and then dispersed across parts of the northern hemisphere, Africa, and ultimately South America. The movement of continents, shifting sea levels, and changing patterns of rainfall and vegetation contributed to the developing landscape of primate biogeography, morphology, and behavior. Today\u2019s primates provide modest reminders of the past diversity and remarkable adaptations of their extinct relatives. This chapter explores the major trends in primate evolution from the origin of the Order Primates to the beginnings of our own lineage, providing a window into these stories from our ancient past.<\/p>\r\n\r\n<h2 class=\"import-Normal\">Major Hypotheses About Primate Origins<\/h2>\r\n<p class=\"import-Normal\">For many groups of mammals, there is a key feature that led to their success. A good example is powered flight in bats. Primates lack a feature like this (see Chapter 5). Instead, if there is something unique about primates, it is probably a group of features rather than one single thing. Because of this, anthropologists and paleontologists struggle to describe an ecological scenario that could explain the rise and success of our own order. Three major hypotheses have been advanced to consider the origin of primates and to explain what makes our order distinct among mammals (Figure 9.1); these are described below.<\/p>\r\n\r\n\r\n[caption id=\"attachment_277\" align=\"aligncenter\" width=\"634\"]<img class=\"wp-image-255\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2023\/03\/8.1.jpg\" alt=\"Primates swinging in tree, eating an insect, and eating fruit.\" width=\"634\" height=\"221\" \/> Figure 9.1: The three major hypotheses are (a) the arboreal hypothesis, (b) the visual predation hypothesis, and (c) the angiosperm-primate coevolution hypothesis. Credit: Primate origin hypotheses original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by <a class=\"rId13\" href=\"https:\/\/marynelsonstudio.com\">Mary Nelson<\/a> is under a <a class=\"rId14\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Arboreal Hypothesis<\/strong><\/h3>\r\n<p class=\"import-Normal\">In the 1800s, many anthropologists viewed all animals in relation to humans. That is, animals that were more like humans were considered to be more \u201cadvanced\u201d and those lacking humanlike features were considered more \u201cprimitive.\u201d This way of thinking was particularly obvious in studies of primates. A more modern way of referring to members of a group that lack certain evolutionary innovations seen in other members is to call them [pb_glossary id=\"1688\"]<strong>plesiomorphic<\/strong>[\/pb_glossary] (literally \u201canciently shaped\u201d). The state of their morphological features is sometimes referred to as [pb_glossary id=\"1689\"]<strong>ancestral<\/strong><strong> traits<\/strong>[\/pb_glossary].<\/p>\r\n<p class=\"import-Normal\">Thus, when anthropologists sought features that separate primates from other mammals, they focused on features that were least developed in lemurs and lorises, more developed in monkeys, and most developed in apes (Figure 9.2). Frederic Wood Jones, one of the leading anatomist-anthropologists of the early 1900s, is usually credited with the Arboreal Hypothesis of primate origins (Jones 1916). This hypothesis holds that many of the features of primates evolved to improve locomotion in the trees; this way of getting around is referred to as arboreal. For example, the grasping hands and feet of primates are well suited to gripping tree branches of various sizes and our flexible joints are good for reorienting the extremities in many different ways. A mentor of Jones, Grafton Elliot Smith, had suggested that the reduced olfactory system, acute vision, and forward-facing eyes of primates are adaptations for making accurate leaps and bounds through a complex, three-dimensional canopy (Smith 1912). The forward orientation of the eyes in primates causes the visual fields to overlap, enhancing depth perception, especially at close range. Evidence to support this hypothesis includes the facts that many extant primates are arboreal, and the plesiomorphic members of most primate groups are dedicated arborealists. The Arboreal Hypothesis was well accepted by most anthropologists at the time and for decades afterward.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"663\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image27-2.png\" alt=\"Diagram shows primates descended from Plesiadapiforms.\" width=\"663\" height=\"543\" \/> Figure 9.2: Primate family tree showing major groups. Disconnected lines show uncertainty about relationships. Two lines lead to tarsiers from different possible groups of origin. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit: <a class=\"rId16\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Primate family tree (Figure 8.2)<\/a> by Jonathan M. G. Perry is under a <a class=\"rId17\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Visual Predation Hypothesis<\/strong><\/h3>\r\n<p class=\"import-Normal\">In the late 1960s and early 1970s, Matt Cartmill studied and tested the idea that the characteristic features of primates evolved in the context of arboreal locomotion. Cartmill noted that squirrels climb trees (and even vertical walls) very effectively, even though they lack some of the key adaptations of primates. As members of the Order Rodentia, squirrels also lack the hand and foot anatomy of primates. They have claws instead of flattened nails and their eyes face more laterally than those of primates. Cartmill reasoned that there must be some other explanation for the unique traits of primates. He noted that some nonarboreal animals share at least some of these traits with primates; for example, cats and predatory birds have forward-facing eyes that enable visual field overlap. Cartmill suggested that the unique suite of features in primates is an adaptation to detecting insect prey and guiding the hands (or feet) to catch insects (Cartmill 1972). His hypothesis emphasizes the primary role of vision in prey detection and capture; it is explicitly comparative, relying on form-function relationships in other mammals and nonmammalian vertebrates. According to Cartmill, many of the key features of primates evolved for preying on insects in this special manner (Cartmill 1974).<\/p>\r\n\r\n<h3 class=\"import-Normal\"><strong>Angiosperm-Primate Coevolution Hypothesis<\/strong><\/h3>\r\n<p class=\"import-Normal\">The visual predation hypothesis was unpopular with some anthropologists. One reason for this is that many primates today are not especially predatory. Another is that, whereas primates do seem well adapted to moving around in the smallest, terminal branches of trees, insects are not necessarily easier to find there. A counterargument to the visual predation hypothesis is the angiosperm-primate coevolution hypothesis. Primate ecologist Robert Sussman (Sussman 1991) argued that the few primates that eat mostly insects often catch their prey on the ground rather than in tree branches. Furthermore, predatory primates often use their ears more than their eyes to detect prey. Finally, most early primate fossils show signs of having been omnivorous rather than insectivorous. Instead, he argued, the earliest primates were probably seeking fruit. Fruit (and flowers) of angiosperms (flowering plants) often develop in the terminal branches. Therefore, any mammal trying to access those fruits must possess anatomical traits that allow them to maintain their hold on thin branches and avoid falling while reaching for the fruits. Primates likely evolved their distinctive visual traits and extremities in the Paleocene (approximately 65 million to 54 million years ago) and Eocene (approximately 54 million to 34 million years ago) epochs, just when angiosperms were going through a revolution of their own\u2014the evolution of large, fleshy fruit that would have been attractive to a small arboreal mammal. Sussman argued that, just as primates were evolving anatomical traits that made them more efficient fruit foragers, angiosperms were also evolving fruit that would be more attractive to primates to promote better seed dispersal. This mutually beneficial relationship between the angiosperms and the primates was termed coevolution or more specifically [pb_glossary id=\"1691\"]<strong>diffuse coevolution<\/strong>.[\/pb_glossary]<\/p>\r\n<p class=\"import-Normal\">At about the same time, D. Tab Rasmussen noted several parallel traits in primates and the South American woolly opossum, <em>Caluromys<\/em>. He argued that early primates were probably foraging on both fruits and insects (Rasmussen 1990). As is true of <em>Caluromys<\/em> today, early primates probably foraged for fruits in the terminal branches of angiosperms, and they probably used their visual sense to aid in catching insects. Insects are also attracted to fruit (and flowers), so these insects represent a convenient opportunity for a primarily fruit-eating primate to gather protein. This solution is a compromise between the visual predation hypothesis and the angiosperm-primate coevolution hypothesis. It is worth noting that other models of primate origins have been proposed, and these include the possibility that no single ecological scenario can account for the origin of primates.<\/p>\r\n\r\n<h2 class=\"import-Normal\">The Origins of Primates<\/h2>\r\n<h3 class=\"import-Normal\"><strong>Paleocene: Mammals in the Wake of Dinosaur Extinctions<\/strong><\/h3>\r\n<p class=\"import-Normal\">Placental mammals, including primates, originated in the Mesozoic Era (approximately 251 million to 65.5 million years ago), the Age of Dinosaurs. During this time, most placental mammals were small, probably nocturnal, and probably avoided predators via camouflage and slow, quiet movement. It has been suggested that the success and diversity of the dinosaurs constituted a kind of ecological barrier to Mesozoic mammals. The extinction of the dinosaurs (and many other organisms) at the end of the Cretaceous Period (approximately 145.5\u201365.5 million years ago) might have opened up these ecological niches, leading to the increased diversity and disparity in mammals of the Tertiary Period (approximately 65.5\u20132.5 million years ago).<\/p>\r\n<p class=\"import-Normal\">The Paleocene was the first epoch in the Age of Mammals. Soon after the Cretaceous-Tertiary (K-T) extinction event, new groups of placental mammals appear in the fossil record. Many of these groups achieved a broad range of sizes and lifestyles as well as a great number of species before declining sometime in the Eocene (or soon thereafter). These groups were ultimately replaced by the modern orders of placental mammals (Figure 9.3). It is unknown whether these replacements occurred gradually, for example by competitive exclusion, or rapidly, perhaps by sudden geographic dispersals with replacement. In some senses, the Paleocene might have been a time of recovery from the extinction event; it was cooler and more seasonal globally than the subsequent Eocene.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"628\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image26.jpg\" alt=\"Person in front of a mural depicting forest animals.\" width=\"628\" height=\"511\" \/> Figure 9.3: A mural of Eocene flora and fauna in North America. Credit: <a class=\"rId19\" href=\"https:\/\/flickr.com\/photos\/126377022@N07\/18404106406\">Image from page 27 of \"Annual report for the year ended June 30 ...\" (1951)<\/a> by <a class=\"rId20\" href=\"https:\/\/flickr.com\/photos\/internetarchivebookimages\/\">Internet Archive Book Images<\/a> has been designated to the <a class=\"rId21\" href=\"https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/\">public domain (CC0)<\/a>. This photograph of the mural \"Fauna and flora of middle Eocene in the Wyoming area\" by Jay Matternes, was originally published by the <a class=\"rId22\" href=\"https:\/\/www.si.edu\/\">Smithsonian<\/a>, and can be viewed in context in the <a class=\"rId23\" href=\"https:\/\/archive.org\/details\/annualreportfory1961united\/page\/7\/mode\/1up?view=theater\">online version of this book<\/a>.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Plesiadapiforms, the Archaic Primates<\/strong><\/h3>\r\n<p class=\"import-Normal\">The Paleocene epoch saw the emergence of several families of mammals that have been implicated in the origin of primates. These are the plesiadapiforms, which are archaic primates, meaning they possessed some primate features and lacked others. The word <em>plesiadapiform <\/em>means \u201calmost adapiform,\u201d a reference to some similarities between some plesiadapiforms and some adapiforms (or adapoids; later-appearing true primates)\u2014mainly in the molar teeth. Because enamel fossilizes better than other parts of the body, the molar teeth are the parts most often found and first discovered for any new species. Thus, dental similarities were often the first to be noticed by early mammalian paleontologists, partly explaining why plesiadapiforms were thought to be primates. Major morphological differences between plesidapiforms and euprimates (true primates) were observed later when more parts of plesiadapiform skeletons were discovered. Many plesiadapiforms have unusual anterior teeth and most have digits possessing claws rather than nails. So far, no plesiadapiform ever discovered has a postorbital bar (seen in extant <strong>[pb_glossary id=\"1712\"]strepsirrhines[\/pb_glossary]<\/strong>) or septum (as seen in <strong>[pb_glossary id=\"1713\"]haplorhines[\/pb_glossary]<\/strong>), and whether or not the <strong>[pb_glossary id=\"1711\"]auditory bulla[\/pb_glossary]<\/strong> was formed by the [pb_glossary id=\"1714\"]<strong>petrosal bone<\/strong> [\/pb_glossary]remains unclear for many plesiadapiform specimens. Nevertheless, there are compelling reasons (partly from new skeletal material) for including plesiadapiforms within the Order Primates.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Geographic and Temporal Distribution<\/em><\/h4>\r\n<p class=\"import-Normal\"><em>Purgatorius<\/em> is generally considered to be the earliest primate. This Paleocene mammal is known from teeth that are very plesiomorphic for a primate. It has some characteristics that suggest it is a basal plesiadapiform, but there is very little to link it specifically with euprimates (see Clemens 2004). Its ankle bones suggest a high degree of mobility, signaling an arboreal lifestyle (Chester et al. 2015). <em>Purgatorius<\/em> is plesiomorphic enough to have given rise to all primates, including the plesiadapiforms. However, new finds suggest that this genus was more diverse and had more differing tooth morphologies than previously appreciated (Wilson Mantilla et al. 2021). Plesiadapiform families were numerous and diverse during parts of the Paleocene in western North America and western Europe, with some genera (e.g., <em>Plesiadapis<\/em>; see Figure 9.4) living on both continents (Figure 9.5). Thus, there were probably corridors for plesiadapiform dispersal between the two continents, and it stands to reason that these mammals were living all across North America, including in the eastern half of the continent and at high latitudes. A few plesiadapiforms have been described from Asia (e.g., <em>Carpocristes<\/em>), but the affinities of these remain uncertain.<\/p>\r\n\r\n<div style=\"text-align: left\">\r\n<table class=\"aligncenter\" style=\"width: 473.25pt\"><caption>Figure 9.4: Families of plesiadapiforms with example genera and traits: a table. Credit: Plesiadapiforms table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId24\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\r\n<thead>\r\n<tr style=\"height: 25pt\">\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\r\n&nbsp;<\/td>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr class=\"Table1-R\" style=\"height: 17pt\">\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Paromomyidae<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Ignacius<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Long, dagger-like, lower incisor.<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">North America and Europe<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early Paleocene to Late Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table1-R\" style=\"height: 18pt\">\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Carpolestidae<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Carpolestes<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Plagiaulacoid dentition. Limb adaptations to terminal branch feeding. Grasping big toe.<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">North America, Europe, and Asia<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle Paleocene to Early Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table1-R\" style=\"height: 16pt\">\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Plesiadapidae<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Plesiadapis<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Mitten-like upper incisor. Diastema. Large body size for group.<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">North America and Europe<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle Paleocene to Early Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table1-R\" style=\"height: 1pt\">\r\n<td class=\"Table1-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\r\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\r\n<\/td>\r\n<td class=\"Table1-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\r\n<p class=\"import-Normal\"><\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n\r\n[caption id=\"attachment_277\" align=\"aligncenter\" width=\"555\"]<img class=\"wp-image-258 \" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image5-5-e1691791897574.png\" alt=\"Global map with not fully formed continents.\" width=\"555\" height=\"308\" \/> Figure 9.5: Map of the world in the Paleocene, highlighting plesiadapiform localities on lands that would become North America, southern Europe, and eastern Asia. Credit: <a class=\"rId26\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Paleocene Map with Plesiadapiform Localities (Figure 8.4)<\/a> original to<a class=\"rId27\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\"> Expl<\/a><a class=\"rId28\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">orations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId29\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId30\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 211.[\/caption]\r\n<h4 class=\"import-Normal\"><em>General Morphological Features<\/em><\/h4>\r\n<p class=\"import-Normal\">Although there is much morphological variation among the families of plesiadapiforms, some common features unite the group. Most plesiadapiforms were small, the largest being about three kilograms (approximately 7 lbs.; <em>Plesiadapis cookei<\/em>). They had small brains and fairly large snouts, with eyes that faced more laterally than in euprimates. Many species show reduction and\/or loss of the canine and anterior premolars, with the resulting formation of a rodent-like <strong>[pb_glossary id=\"1172\"]diastema[\/pb_glossary] <\/strong>(a pronounced gap between the premolars and the incisors, with loss of at least the canine); this probably implies a herbivorous diet. Some families appear to have had very specialized diets, as suggested by unusual tooth and jaw shapes.<\/p>\r\n<p class=\"import-Normal\">Arguably the most interesting and unusual family of plesiadapiforms is the Carpolestidae. They are almost exclusively from North America (with a couple of possible members from Asia), and mainly from the Middle and Late Paleocene. Their molars are not very remarkable, being quite similar to those of some other plesiadapiforms (e.g., Plesiadapidae). However, their lower posterior premolars (p4) are laterally compressed and blade-like with vertical serrations topped by tiny cuspules. This unusual dental morphology is termed [pb_glossary id=\"1693\"]<strong><em>plagiaulacoid<\/em><\/strong> [\/pb_glossary] (Simpson 1933). The upper premolar occlusal surfaces are broad and are covered with many small cuspules; the blade-like lower premolar might have cut across these cuspules, between them, or both.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"357\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image13-5.png\" alt=\"Front view of skull with pointed teeth.\" width=\"357\" height=\"322\" \/> Figure 9.25: Skull of Victoriapithecus macinnesi. Credit: Victoriapithecus macinnesi skull photo taken at the Musee d'Histoire Naturelle, Paris by Ghedoghedo is under a CC BY-SA 3.0 License.[\/caption]\r\n<p class=\"import-Normal\">Many plesiadapiforms have robust limb bones with hallmarks of arboreality. Instead of having nails, most taxa had sharp claws on most or all of the digits. The extremities show grasping abilities comparable to those of primates and some arboreal marsupials. Nearly complete skeletons have yielded a tremendous wealth of information on locomotor and foraging habits. Many plesiadapiforms appear to have been able to cling to vertical substrates (like a broad tree trunk) using their sharp claws, propelling themselves upward using powerful hindlimbs, bounding along horizontal supports, grasping smaller branches, and moving head-first down tree trunks. In carpolestids in particular, the skeleton appears to have been especially well adapted to moving slowly and carefully in small terminal branches (Figure 9.6).<\/p>\r\n\r\n<\/div>\r\n<div class=\"textbox shaded\">\r\n<h3 class=\"import-Normal\">Dig Deeper: Debate: Relationship of Plesiadapiforms to True Primates<\/h3>\r\n<p class=\"import-Normal\">In the middle of the twentieth century, treeshrews (Order Scandentia) were often considered part of the Order Primates, based on anatomical similarities between some treeshrews and primates. For many people, plesiadapiforms represented intermediates between primates and treeshrews, so plesiadapiforms were included in Primates as well.<\/p>\r\n<p class=\"import-Normal\">Studies of reproduction and brain anatomy in treeshrews and lemurs suggested that treeshrews are not primates (e.g., Martin 1968). This was soon followed by the suggestion to also expel plesiadapiforms (Martin 1972) from the Order Primates. Like treeshrews, plesiadapiforms lack a postorbital bar, nails, and details of the ear region that characterize true primates. Many paleoanthropologists were reluctant to accept this move to banish plesiadapiforms (e.g., F. S. Szalay, P. D. Gingerich).<\/p>\r\n<p class=\"import-Normal\">Later, K. Christopher Beard (1990) found that in some ways, the digits of paromomyid plesiadapiforms are actually more similar to those of dermopterans (Order Dermoptera), the closest living relatives of primates, than they are to those of primates themselves (but see Krause 1991). At the same time, Richard Kay and colleagues (1990) found that cranial circulation patterns and auditory bulla morphology in the paromomyid, <em>Ignacius <\/em>(see Figure 9.4), are more like those of dermopterans than of primates.<\/p>\r\n<p class=\"import-Normal\">For many anthropologists, this one-two punch effectively removed plesiadapiforms from the Order Primates. In the last two decades, the tide of opinion has turned again, with many researchers reinstating plesiadapiforms as members of the Order Primates. New and more complete specimens demonstrate that the postcranial skeletons of plesiadapiforms, including the hands and feet, were primate-like, not dermorpteran-like (Bloch and Boyer 2002, 2007). New fine-grained CT scans of relatively complete plesiadapiform skulls revealed that they share some key traits with primates to the exclusion of other placental mammals (Bloch and Silcox 2006). Most significant was the suggestion that <em>Carpolestes simpsoni <\/em>possessed an auditory bulla formed by the [pb_glossary id=\"1696\"]<strong>petrosal <\/strong><strong>bone<\/strong>[\/pb_glossary], like in all living primates.<\/p>\r\n<p class=\"import-Normal\">The debate about the status of plesiadapiforms continues, owing to a persistent lack of key bones in some species and owing to genuine complexity of the anatomical traits involved. Maybe plesiadapiforms were the ancestral stock from which all primates arose, with some plesiadapiforms (e.g., carpolestids) nearer to the primate <strong>[pb_glossary id=\"1723\"]stem[\/pb_glossary]<\/strong> than others.<\/p>\r\n\r\n<\/div>\r\n<div class=\"__UNKNOWN__\">\r\n<h3 class=\"import-Normal\"><strong>Adapoids and Omomyoids, the First True Primates<\/strong><\/h3>\r\n<h4 class=\"import-Normal\"><em>Geographic and Temporal Distribution<\/em><\/h4>\r\n<p class=\"import-Normal\">The first universally accepted fossil primates are the adapoids (Superfamily [pb_glossary id=\"1695\"]<strong>Adapoidea<\/strong>[\/pb_glossary]) and the omomyoids (Superfamily <strong>[pb_glossary id=\"1694\"]Omomyoidea[\/pb_glossary])<\/strong>. These groups become quite distinct over evolutionary time, filling mutually exclusive niches for the most part. However, the earliest adapoids are very similar to the earliest omomyoids.<\/p>\r\n<p class=\"import-Normal\">The adapoids were mainly diurnal and herbivorous, with some achieving larger sizes than any plesiadapiforms (10 kg; 22 lbs.). By contrast, the omomyoids were mainly nocturnal, insectivorous and frugivorous, and small.<\/p>\r\n<p class=\"import-Normal\">Both groups appear suddenly at the start of the Eocene, where they are present in western North America, western Europe, and India (Figure 9.7). This wide dispersal of early primates was probably due to the presence of rainforest corridors extending far into northern latitudes.<\/p>\r\n\r\n\r\n[caption id=\"attachment_277\" align=\"aligncenter\" width=\"539\"]<img class=\"wp-image-260\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image22-3-e1691792023503.png\" alt=\"Global map with not fully formed continents and omomyoid localities.\" width=\"539\" height=\"317\" \/> Figure 9.7: Map of the world in the Eocene, highlighting adapoid and omomyoid localities on lands that would become North America, southern Europe, Africa, and Asia. Credit: <a class=\"rId36\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Eocene Map with Adapoid and Omomyoid Localities (Figure 8.6)<\/a> original to <a class=\"rId37\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId38\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId39\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 229.[\/caption]\r\n<p class=\"import-Normal\">In North America and Europe, both groups achieved considerable diversity in the Middle Eocene, then mostly died out at the end of that epoch (Figure 9.8). In some Eocene rock formations in the western United States, adapoids and omomyoids make up a major part of the mammalian fauna. The Eocene of India has yielded a modest diversity of euprimates, some of which are so plesiomorphic that it is difficult to know whether they are adapoids or omomyoids (or even early anthropoids).<\/p>\r\n\r\n<div style=\"text-align: left\">\r\n<table class=\"aligncenter\" style=\"width: 473.25pt\"><caption>Figure 9.8: Families of adapoids and omomyoids with example genera and traits: a table. Credit: Adapoids and omomyoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId40\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\r\n<thead>\r\n<tr style=\"height: 25pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\r\n&nbsp;<\/td>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr class=\"Table2-R\" style=\"height: 18pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Cercamoniidae<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Donrussellia<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Variable in tooth number and jaw shape.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Europe and Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early to Late Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Asiadapidae<sup>2<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Asiadapis<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Plesiomorphic teeth and jaw resemble early Omomyids.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Caenopithecidae<sup>3<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Darwinius<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Robust jaws with crested molars. Fewer premolars.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Europe, Africa, North America, and Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle to Late Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Adapidae<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Adapis<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Fused mandible. Long molar crests. Large size and large chewing muscles.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Europe<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Late Eocene to Early Oligocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Sivaladapidae<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Sivaladapis<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Some large with robust jaws.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle Eocene to Late Miocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Notharctidae<sup>4<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Notharctus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Canine sexual dimorphism. Lemur-like skull. Clinging and leaping adaptations.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">North America and Europe<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early to Middle Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Omomyidae<sup>5<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Teilhardina<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Small, nocturnal, frugivorous or insectivorous. Tarsier-like skull in some.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">North America, Europe, and Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early Eocene to Early Miocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 16pt\">\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Microchoeridae<sup>6<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Necrolemur<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Long bony ear tubes. Tarsier-like lower limb adaptations for leaping.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Europe and Asia<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Early Eocene to Early Oligocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table2-R\" style=\"height: 1pt\">\r\n<td class=\"Table2-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\r\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\r\n<p class=\"import-Normal\"><sup>2<\/sup> See Dunn et al. 2016 and Rose et al. 2018.<\/p>\r\n<p class=\"import-Normal\"><sup>3<\/sup> See Kirk and Williams 2011 and Seiffert et al. 2009.<\/p>\r\n<p class=\"import-Normal\"><sup>4<\/sup> See Gregory 1920.<\/p>\r\n<p class=\"import-Normal\"><sup>5<\/sup> See Beard and MacPhee 1994 and Strait 2001.<\/p>\r\n<p class=\"import-Normal\"><sup>6<\/sup> See Schmid 1979.<\/p>\r\n<\/td>\r\n<td class=\"Table2-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\r\n<p class=\"import-Normal\"><\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n<p class=\"import-Normal\">Adapoids and omomyoids barely survived the Eocene-Oligocene extinctions, when colder temperatures, increased seasonality, and the retreat of rainforests to lower latitudes led to changes in mammalian biogeography. In North America, one genus (originally considered an omomyoid but recently reclassified as Adapoidea) persisted until the Miocene: <em>Ekgmowechashala<\/em> (Rose and Rensberger 1983). This taxon has highly unusual teeth and might have been a late immigrant to North America from Asia. In Asia, one family of adapoids, the Sivaladapidae, retained considerable diversity as late as the Late Miocene.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Adapoid Diversity<\/em><\/h4>\r\n<p class=\"import-Normal\">Adapoids were very diverse, particularly in the Eocene of North America and Europe. They can be divided into six families, with a few species of uncertain familial relationship. As a group, adapoids have some features in common, although much of what they share is plesiomorphic. Important features include the hallmarks of euprimates: postorbital bar, flattened nails, grasping extremities, and a petrosal bulla (Figures 9.9 and 9.10). In addition, some adapoids retain the ancestral dental formula of 2.1.4.3; that is, in each quadrant of the mouth, there are two incisors, one canine, four premolars, and three molars. In general, the incisors are small compared to the molars, but the canines are relatively large, with sexual dimorphism in some species. Cutting crests on the molars are well developed in some species, and the two halves of the mandible were fused at the midline in some species. Some adapoids were quite small (<em>Anchomomys <\/em>at a little over 100 g), and some were quite large (<em>Magnadapis<\/em> at 10 kg; 22 lbs.). Furthermore, the spaces and attachment features for the chewing muscles were truly enormous in some species, suggesting that these muscles were very large and powerful. Taken together, this suggests an overall adaptive profile of diurnal herbivory. The canine sexual dimorphism in some species suggests a possible mating pattern of polygyny, as males in polygynous primate species often compete with each other for mates and have especially large canine teeth.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"548\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image18-1.jpg\" alt=\"Three partial animal crania.\" width=\"548\" height=\"350\" \/> Figure 9.9: Representative crania of Adapidae from Museum d\u2019Histoire Naturelle Victor Brun, a natural history museum in Montauban, France. The white scale bar is 1 cm long. Credit: <a class=\"rId43\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Representative crania of adapids (European adapoids, (Figure 8.7)<\/a> from the <a class=\"rId44\" href=\"https:\/\/www.museum.montauban.com\/\">Museum d\u2019Histoire Naturelle Victor Brun in Montauban, France<\/a> original to <a class=\"rId45\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology <\/a>by Jonathan M. G. Perry is under a <a class=\"rId46\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"547\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image19-2.jpg\" alt=\"Side views of small rodentlike skeleton with long tail.\" width=\"547\" height=\"525\" \/> Figure 9.10: Darwinius masillae, a member of the Caenopithecidae. The slab on the left is Plate A and the slab on the right is Plate B. The parts of the skeleton in B that are outside of the dashed lines were fabricated. Credit: <a class=\"rId48\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Darwinius%20masillae%20holotype%20slabs.jpg\">Darwinius masillae holotype slabs<\/a> by Jens L. Franzen, Philip D. Gingerich, J\u00f6rg Habersetzer1, J\u00f8rn H. Hurum, Wighart von Koenigswald, B. Holly Smith is under a <a class=\"rId49\" href=\"https:\/\/creativecommons.org\/licenses\/by\/2.5\/legalcode\">CC BY 2.5 License<\/a>. Originally from Franzen et al. 2009.[\/caption]\r\n<h4 class=\"import-Normal\"><em>Omomyoid Diversity<\/em><\/h4>\r\n<p class=\"import-Normal\">Like adapoids, omomyoids appeared suddenly at the start of the Eocene and then became very diverse with most species dying out before the Oligocene. Omomyoids are known from thousands of jaws with teeth, relatively complete skulls for about a half-dozen species, and very little postcranial material. Omomyoids were relatively small primates, with the largest being less than three kilograms (approximately 7 lbs.; <em>Macrotarsius montanus<\/em>). All known crania possess a postorbital bar, which in some has been described as \u201cincipient closure.\u201d Some\u2014but not all\u2014known crania have an elongated bony ear tube extending lateral to the location of the eardrum, a feature seen in living tarsiers and <strong>[pb_glossary id=\"2568\"]catarrhines[\/pb_glossary]<\/strong>. The anterior teeth tend to be large, with canines that are usually not much larger than the incisors. Often it is difficult to distinguish closely related species using molar morphology, but the premolars tend to be distinct from one species to another. The postcranial skeleton of most omomyoids shows hallmarks of leaping behavior reminiscent of that of tarsiers. In North America, omomyoids became very diverse and abundant. In fact, omomyoids from Wyoming are sufficiently abundant and from such stratigraphically controlled conditions that they have served as strong evidence for the gradual evolution of anatomical traits over time (Rose and Bown 1984).<\/p>\r\n<p class=\"import-Normal\"><em>Teilhardina <\/em>(Figure 9.11; see Figure 9.2) is one of the earliest and arguably the most plesiomorphic of omomyoids. <em>Teilhardina<\/em> has several species, most of which are from North America, with one from Europe (<em>T. belgica<\/em>) and one from Asia (<em>T. asiatica<\/em>). The species of this genus are anatomically similar and the deposits from which they are derived are roughly contemporaneous. Thus, this small primate likely dispersed across the northern continents very rapidly (Smith et al. 2006).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"545\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image3-1.jpg\" alt=\"World map with primates jumping across forested areas.\" width=\"545\" height=\"289\" \/> Figure 9.11: A map of the world during the early Eocene showing one hypothesis for the direction of dispersal of the omomyoid Teilhardina. The map depicts primates hopping from continent to continent (East to West) via the forest corridors at high latitudes. Credit: <a href=\"https:\/\/www.pnas.org\/content\/103\/30\/11223\">Paleogeographic map showing hypothetical migration routes of Teilhardina (Figure 1)<\/a> by Thierry Smith, Kenneth D. Rose, and Philip D. Gingerich. 2006. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America <\/a>103 (30): 11223\u201311227. Copyright (2006) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a>[\/caption]\r\n<h2 class=\"import-Normal\">The Emergence of Modern Primate Groups<\/h2>\r\n<h3 class=\"import-Normal\"><strong>Origins of Crown Strepsirrhines<\/strong><\/h3>\r\n<p class=\"import-Normal\">Until the turn of this century, very little was known about the origins of the <strong>[pb_glossary id=\"1698\"]crown[\/pb_glossary]<\/strong> (living) strepsirrhines. The Quaternary record of Madagascar contains many amazing forms of lemurs, including giant sloth-like lemurs, lemurs with perhaps monkey-like habits, lemurs with koala-like habits, and even a giant aye-aye (Godfrey and Jungers 2002). However, in Madagascar, early Tertiary continental sediments are lacking, and there is no record of lemur fossils before the Pleistocene.<\/p>\r\n<p class=\"import-Normal\">The fossil record of galagos is slightly more informative. Namely, there are Miocene African fossils that are very likely progenitors of lorisids (Simpson 1967). However, these are much like modern galagos and do not reveal anything about the relationship between crown strepsirrhines and Eocene fossil primates (but see below regarding <em>Propotto<\/em>). A similar situation exists for lorises in Asia: there are Miocene representatives, but these are substantially like modern lorises. The discovery of the first definite [pb_glossary id=\"1699\"]<strong>toothcomb<\/strong>[\/pb_glossary] canine (a hallmark of stresirrhines) in 2003 provided the \u201csmoking gun\u201d for the origin of crown strepsirrhines (Seiffert et al. 2003). Recently, several other African primates have been recognized as having strepsirrhine affinities (Marivaux et al. 2013; Seiffert 2012). The enigmatic Fayum primate <em>Plesiopithecus<\/em> is known from a skull that has been compared to aye-ayes and to lorises (Godinot 2006; Simons and Rasmussen 1994a).<\/p>\r\n<p class=\"import-Normal\">The now-recognized diversity of stem strepsirrhines from the Eocene and Oligocene of Afro-Arabia is strong evidence to suggest that strepsirrhines originated in that geographic area. This implies that lorises dispersed to Asia subsequent to an African origin. It is unknown what the first strepsirrhines in Madagascar were like. However, it seems likely that the lemuriform-lorisiform split occurred in continental Africa, followed by dispersal of lemuriform stock to Madagascar. Recent evidence suggests that <em>Propotto<\/em>, a Miocene primate from Kenya originally described as a potto antecedent, actually forms a clade with <em>Plesiopithecus <\/em>and the aye-aye; this might suggest that strepsirrhines dispersed to Madagascar from continental Africa more than once (Gunnell et al. 2018).<\/p>\r\n\r\n<h3 class=\"import-Normal\"><strong>The Fossil Record of Tarsiers<\/strong><\/h3>\r\n<p class=\"import-Normal\">Tarsiers are so unusual that they fuel major debates about primate taxonomy. Tarsiers today are moderately diverse but geographically limited and not very different in their ecological habits\u2014especially considering that the split between them and their nearest living relative probably occurred over 50 million years ago. If omomyoids are excluded, then the fossil record of tarsiers is very limited. Two fossil species from the Miocene of Thailand have been placed in the genus <em>Tarsius<\/em>, as has an Eocene fossil from China (Beard et al. 1994). These, and <em>Xanthorhysis<\/em> from the Eocene of China, are all very tarsier-like. In fact, it is striking that <em>Tarsius eocaenus<\/em> from China was already so tarsier-like as early as the Eocene. This suggests that tarsiers achieved their current morphology very early in their evolution and have remained more or less the same while other primates changed dramatically. Two additional genera, <em>Afrotarsius<\/em> from the Oligocene of Egypt and Libya and <em>Afrasia<\/em> from the Eocene of Myanmar, have also been implicated in tarsier origins, though the relationship between them and tarsiers is unclear (Chaimanee et al. 2012). More recently, a partial skeleton of a small Eocene primate from China, <em>Archicebus achilles<\/em> (dated to approximately 55.8 million to 54.8 million years ago), was described as the most basal tarsiiform (Ni et al. 2013). This primate is reconstructed as a diurnal insectivore and an arboreal quadruped that did some leaping\u2014but not to the specialized degree seen in living tarsiers. The anatomy of the eye in living tarsiers suggests that their lineage passed through a diurnal stage, so <em>Archicebus<\/em> (and diurnal omomyoids) might represent such a stage.<\/p>\r\n\r\n<h3 class=\"import-Normal\"><strong>Climate Change and the Paleogeography of Modern Primate Origins<\/strong><\/h3>\r\n<p class=\"import-Normal\">Changing global climate has had profound effects on primate dispersal patterns and ecological habits over evolutionary time. Primates today are strongly tied to patches of trees and particular plant parts such as fruits, seeds, and immature leaves. It is no surprise, then, that the distribution of primates mirrors the distribution of forests. Today, primates are most diverse in the tropics, especially in tropical rainforests. Global temperature trends across the Tertiary have affected primate ranges. Following the Cretaceous-Tertiary extinction event, cooler temperatures and greater seasonality characterized the Paleocene. In the Eocene, temperatures (and probably rainfall) increased globally and rainforests likely extended to very high latitudes. During this time, euprimates became diverse. With cooling and increased aridity at the end of the Eocene, many primate extinctions occurred in the northern continents and the surviving primates were confined to lower latitudes in South America, Afro-Arabia, Asia, and southern Europe. Among these survivors are the progenitors of the living groups of primates: lemurs and lorises, tarsiers, [pb_glossary id=\"1700\"]<strong>platyrrhines<\/strong>[\/pb_glossary] (monkeys of the Americas), and catarrhines (monkeys and apes of Africa and Asia) (Figure 9.12).<\/p>\r\n\r\n\r\n[caption id=\"attachment_277\" align=\"aligncenter\" width=\"539\"]<img class=\"wp-image-264\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image2-5-e1691791570984.png\" alt=\"Map of world with gray continents.\" width=\"539\" height=\"306\" \/> Figure 9.12: Map of key localities of early anthropoids on land that becomes Africa and southern Asia. Credit: <a class=\"rId56\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Oligocene Map with Key Early Anthropoid Localities (Figure 8.10)<\/a> original to <a class=\"rId57\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId58\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId59\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 265.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Competing Hypotheses for the Origin of Anthropoids<\/strong><\/h3>\r\n<p class=\"import-Normal\">There is considerable debate among paleoanthropologists as to the geographic origins of anthropoids. In addition, there is debate regarding the source group for anthropoids. Three different hypotheses have been articulated in the literature. These are the adapoid origin hypothesis, the omomyoid origin hypothesis, and the tarsier origin hypothesis (Figure 9.13).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"419\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image24-1-1.jpg\" alt=\"Diagrams show three relationships among primate groups.\" width=\"419\" height=\"742\" \/> Figure 9.13: Competing models of anthropoid origins. Branch lengths are not to scale. The omomyoid origin model and tarsier origin model do not make specific reference to the evolutionary position of strepsirrhines; however, they were included here for completeness. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\">A full text description of this image is available<\/a>. Credit: <a class=\"rId61\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Competing Trees for Anthropoid Origins (Figure 8.11)<\/a> original to <a class=\"rId62\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Jonathan M. G. Perry is under a <a class=\"rId63\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<h4 class=\"import-Normal\"><em>Adapoid Origin Hypothesis<\/em><\/h4>\r\n<p class=\"import-Normal\">Resemblances between some adapoids and some extant anthropoids include fusion of the [pb_glossary id=\"1702\"]<strong>mandibular symphysis<\/strong>[\/pb_glossary], overall robusticity of the chewing system, overall large body size, features that signal a diurnal lifestyle (like relatively small eye sockets), and ankle bone morphology. Another feature in common is canine sexual dimorphism, which is present in some species of adapoids (probably) and in several species of anthropoids.<\/p>\r\n<p class=\"import-Normal\">These features led some paleoanthropologists in the last half of the 20th century to suggest that anthropoids came from adapoid stock (Gingerich 1980; Simons and Rasmussen 1994b). One of the earliest supporters of the link between adapoids and anthropoids was Hans Georg Stehlin, who described much of the best material of adapoids and compared these Eocene primates to South American monkeys (Stehlin 1912). In more recent times, the adapoid origin hypothesis was reinforced by resemblances between these European adapoids (especially <em>Adapis <\/em>and <em>Leptadapis<\/em>) and some early anthropoids from the Fayum Basin (e.g., <em>Aegyptopithecus<\/em>, see below; Figure 9.14).<\/p>\r\n\r\n<div style=\"text-align: left\">\r\n<table class=\"aligncenter\" style=\"width: 473.25pt\"><caption>Figure 9.14: Families of early anthropoids with example genera and traits: a table. Credit: Early anthropoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId64\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\r\n<thead>\r\n<tr style=\"height: 25pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\r\n&nbsp;<\/td>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr class=\"Table3-R\" style=\"height: 18pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Propliopithecidae<sup>2<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Aegyptopithecus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Large size. Cranial sexual dimorphism, large canines. Robust jaws and rounded molars. Partially ossified ear tube (in some). Robust skeleton; quadruped.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Africa<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Late Eocene to Early Oligocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 16pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Parapithecidae<sup>3<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Apidium<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Medium size. Retention of three premolars per quadrant. Rounded molars and premolars with large central cusps. Adaptations for leaping in the lower limb.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Africa<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Late Eocene to Late Oligocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 16pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Proteopithecidae<sup>4<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Proteopithecus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Small size. Retention of three premolars per quadrant. Arboreal quadrupeds that ate fruit.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Africa<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Late Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 16pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Oligopithecidae<sup>5<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Catopithecus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Small size. Skull has postorbital septum and unfused mandible. Deep jaws. Diet of fruits. Generalized quadruped.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Africa<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Late Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 16pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Eosimiidae<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Eosimias<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Deep jaw with vertical unfused symphysis. Pointed incisors and canines. Crowded premolars.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Asia<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle Eocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 16pt\">\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Amphipithecidae<sup>6<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\"><em>Pondaungia<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Deep jaws. Molars generally rounded with wide basins.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Asia<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\r\n<p class=\"import-Normal\">Middle Eocene to Early Oligocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table3-R\" style=\"height: 1pt\">\r\n<td class=\"Table3-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\r\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\r\n<p class=\"import-Normal\"><sup>2<\/sup> See Gebo and Simons 1987 and Simons et al. 2007.<\/p>\r\n<p class=\"import-Normal\"><sup>3<\/sup> See Feagle and Simons 1995 and Simons 2001.<\/p>\r\n<p class=\"import-Normal\"><sup>4<\/sup> See Simons and Seiffert 1999.<\/p>\r\n<p class=\"import-Normal\"><sup>5<\/sup> See Simons and Rasmussen 1996.<\/p>\r\n<p class=\"import-Normal\"><sup>6<\/sup> See Kay et al. 2004.<\/p>\r\n<\/td>\r\n<td class=\"Table3-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\r\n<p class=\"import-Normal\"><\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<td><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n<p class=\"import-Normal\">Unfortunately for the adapoid hypothesis, most of the shared features listed above probably emerged independently in the two groups as adaptations to a diet of hard and\/or tough foods. For example, fusion of the mandibular symphysis likely evolved as a means to strengthen the jaw against forces that would pull the two halves away from each other, in the context of active chewing muscles on both sides of the head generating great bite forces. This context would also favor the development of robust jaws, large chewing muscles, shorter faces, and some other features shared by some adapoids and some anthropoids.<\/p>\r\n<p class=\"import-Normal\">As older and more plesiomorphic anthropoids were found in the Fayum Basin, it became clear that the earliest anthropoids from Africa did not possess these features of jaw robusticity (Seiffert et al. 2009). Furthermore, many adapoids never evolved these features. Fusion of the mandibular symphysis in adapoids is actually quite different from that in anthropoids and probably occurred during juvenile development in the former (Beecher 1983; Ravosa 1996). Eventually, the adapoid origin hypothesis fell out of favor among most paleoanthropologists, although the description of <em>Darwinius<\/em> is a recent revival of that idea (Franzen et al. 2009; but see Seiffert et al. 2009, Williams et al. 2010b).<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Omomyoid Origin Hypothesis<\/em><\/h4>\r\n<p class=\"import-Normal\">Similarities in cranial and hindlimb morphology between some omomyoids and extant tarsiers have led to the suggestion that tarsiers arose from some kind of omomyoid. In particular, <em>Necrolemur<\/em> has many features in common with tarsiers, as does the North American <em>Shoshonius<\/em>, which is known from a few beautifully preserved (although distorted) crania. Tarsiers and <em>Shoshonius <\/em>share exclusively some features of the base of the cranium; however, <em>Shoshonius<\/em> does not have any sign of postorbital closure, and it lacks the bony ear tube of tarsiers. Nevertheless, some of the resemblances between some omomyoids and tarsiers suggest that tarsiers might have originated from within the Omomyoidea (Beard 2002; Beard and MacPhee 1994). In this scenario, although living tarsiers and living anthropoids might be sister taxa, they might have evolved from different omomyoids, possibly separated from each other by more than 50 million years of evolution, or from anthropoids evolved from some non-omomyoid fossil group. The arguments against the omomyoid origin hypothesis are essentially the arguments <em>for<\/em> the tarsier origin hypothesis (see below). Namely, tarsiers and anthropoids share many features (especially of the soft tissues) that must have been retained for many millions of years or must have evolved convergently in the two groups. Furthermore, a key hard-tissue feature shared between the two extant groups, the postorbital septum, was not present in any omomyoid. Therefore, that feature must have arisen convergently in the two extant groups or must have been lost in omomyoids. Neither scenario is very appealing, although recent arguments for <strong>convergent evolution<\/strong> of the postorbital septum in tarsiers and anthropoids have arisen from embryology and histology of the structure (DeLeon et al. 2016).<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Tarsier Origin Hypothesis<\/em><\/h4>\r\n<p class=\"import-Normal\">Several paleoanthropologists have suggested that there is a relationship between tarsiers and anthropoids to the exclusion of omomyoids and adapoids (e.g., Cartmill and Kay 1978; Ross 2000; Williams and Kay 1995). Tarsiers and anthropoids today share several traits, including many soft-tissue features related to the olfactory system (e.g., the loss of a hairless external nose and loss of the median cleft running from the nose to the mouth, as possessed by strepsirrhines), and aspects of the visual system (e.g., the loss of a reflective layer at the back of the eye, similarities in carotid circulation to the brain, and mode of placentation). Unfortunately, none of these can be assessed directly in fossils. Some bony similarities between tarsiers and anthropoids include an extra air-filled chamber below the middle ear cavity, reduced bones within the nasal cavity, and substantial postorbital closure; these can be assessed in fossils, but the distribution of these traits in omomyoids does not yield clear answers. Furthermore, several similarities between tarsiers and anthropoids are probably due to similarities in sensory systems, which might have evolved in parallel for ecological reasons. Although early attempts to resolve the crown primates with molecular data were sometimes equivocal or in disagreement with one another, more recent analyses (including those of short interspersed elements) suggest that tarsiers and anthropoids are sister groups to the exclusion of lemurs and lorises (Williams et al. 2010a). However, this does not address omomyoids, all of which are far too ancient for DNA extraction.<\/p>\r\n<p class=\"import-Normal\">The above three hypotheses are not the only possibilities for anthropoid origins. It may be that anthropoids are neither the closest sister group of tarsiers, nor evolved from adapoids or omomyoids. In recent years, two new groups of Eocene Asian primates have been implicated in the origin of anthropoids: the eosimiids and the amphipithecids. It is possible that one or the other of these two groups gave rise to anthropoids. Regardless of the true configuration of the tree for crown primates, the three major extant groups probably diverged from each other quite long ago (Seiffert et al. 2004).<\/p>\r\n\r\n<h3 class=\"import-Normal\"><strong>Early Anthropoid Fossils in Africa<\/strong><\/h3>\r\n[caption id=\"\" align=\"aligncenter\" width=\"526\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image7-2.jpg\" alt=\"People digging in a sandy desert.\" width=\"526\" height=\"352\" \/> Figure 9.15: Egyptian workers sweeping Quarry I in the Fayum Basin (2004). This technique, called wind harvesting, removes the desert crust and permits wind to blow out fine sediment and reveal fossils. Credit: <a class=\"rId66\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Egyptian workers sweeping Quarry I in the Fayum Basin (2004, Figure 8.12)<\/a> by Jonathan M. G. Perry is under a <a class=\"rId67\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"280\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image14-2.jpg\" alt=\"A person using a tool to expose bone in sand.\" width=\"280\" height=\"423\" \/> Figure 9.16: Elwyn Laverne Simons excavating Aegyptopithecus in the Fayum Basin. Credit: <a class=\"rId69\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Elwyn Laverne Simons in the Fayum Basin (Figure 8.13)<\/a> used by permission of the <a class=\"rId70\" href=\"https:\/\/lemur.duke.edu\/\">Duke Lemur Center,<\/a> Division of Fossil Primates, is under a <a class=\"rId71\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<p class=\"import-Normal\">The classic localities yielding the greatest wealth of early anthropoid fossils are those from the Fayum Basin in Egypt (Simons 2008; Figure 9.15). The Fayum is a veritable oasis of fossil primates in an otherwise spotty early Tertiary African record. Since the 1960s, teams led by E. L. Simons have discovered several new species of early anthropoids, some of which are known from many parts of the skeleton and several individuals (Figure 9.16).<\/p>\r\n<p class=\"import-Normal\">The Fayum Jebel Qatrani Formation and Birket Qarun Formation between them have yielded a remarkable array of terrestrial, arboreal, and aquatic mammals. These include ungulates, bats, sea cows, elephants, hyraces, rodents, whales, and primates. Also, many other vertebrates, like water birds, were present. The area at the time of deposition (Late Eocene through Early Oligocene) was probably very wet, with slow-moving rivers, standing water, swampy conditions, and lots of trees (see Bown and Kraus 1988). In short, it was an excellent place for primates.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>General Morphology of Anthropoids<\/em><\/h4>\r\n<p class=\"import-Normal\">The anthropoids known from the Fayum (and their close relatives from elsewhere in East Africa and Afro-Arabia) bear many of the anatomical hallmarks of extant anthropoids; however, there are plesiomorphic forms in several families that lack one or more anthropoid traits. All Fayum anthropoids known from skulls possess postorbital closure, most had fused mandibular symphyses, and most had ring-like [pb_glossary id=\"1704\"]<strong>ectotympanic<\/strong> [\/pb_glossary] bones. Tooth formulae were generally either 2.1.3.3 or 2.1.2.3. Fayum anthropoids ranged in size from the very small <em>Qatrania<\/em> and <em>Biretia <\/em>(less than 500 g) to the much-larger <em>Aegyptopithecus<\/em> (approximately 7 kg; 15 lbs.). Fruit was probably the main component of the diet for most or all of the anthropoids, with some of them supplementing with leaves (Kay and Simons 1980; Kirk and Simons 2001; Teaford et al. 1996). Most Fayum anthropoids were probably diurnal above-branch quadrupeds. Some of them (e.g., <em>Apidium<\/em>; see Figure 9.14) were probably very good leapers (Gebo and Simons 1987), but none show specializations for gibbon-style suspensory locomotion. Some of the Fayum anthropoids are known from hundreds of individuals, permitting the assessment of individual variation, sexual dimorphism, and in some cases growth and development. The description that follows provides greater detail for the two best known Fayum anthropoid families, the Propliopithecidae and the Parapithecidae; the additional families are summarized briefly.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Fayum Anthropoid Families<\/em><\/h4>\r\n<p class=\"import-Normal\">The Propliopithecidae (see Figure 9.14) include the largest anthropoids from the fauna, and they are known from several crania and some postcranial elements. They have been suggested to be stem catarrhines, although perhaps near the split between catarrhines and platyrrhines. The best known propliopithecid is <em>Aegyptopithecus<\/em>, known from many teeth, crania, and postcranial elements (Figure 9.17) .<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"431\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image4-2-1.jpg\" alt=\"Two animal skull side views.\" width=\"431\" height=\"281\" \/> Figure 9.17: Female (left) and male (right) skull material for Aegyptopithecus zeuxis. The mandibles are not associated with the crania. Credit: <a href=\"https:\/\/www.pnas.org\/doi\/full\/10.1073\/pnas.0703129104#supplementary-materials\">Female and male cranium of A. zeuxi (03129Fig5, Supporting Information)<\/a> by Elwyn L. Simons, Erik R. Seiffert, Timothy M. Ryan, and Yousry Attia. 2007. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America<\/a> 104 (21): 8731\u20138736. Copyright (2007) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a>[\/caption]\r\n<p class=\"import-Normal\">Parapithecidae are an extremely abundant and unusual family of anthropoids from the Fayum. The parapithecid <em>Apidium<\/em> is known from many jaws with teeth, crushed and distorted crania, and several skeletal elements. <em>Parapithecus<\/em> is known from cranial material including a beautiful, undistorted cranium. This genus shows extreme reduction of the incisors, including complete absence of the lower incisors in <em>P. grangeri <\/em>(Simons 2001). This trait is unique among primates. Parapithecids were once thought to be the ancestral stock of platyrrhines; however, their platyrrhine-like features are probably ancestral retentions, so the most conservative approach is to consider them stem anthropoids.<\/p>\r\n<p class=\"import-Normal\">The Proteopithecidae were small frugivores that probably mainly walked along horizontal branches on all fours. They are considered stem anthropoids. The best known genus, <em>Proteopithecus<\/em>, is represented by dentitions, crania, and postcranial elements.<\/p>\r\n<p class=\"import-Normal\">The Oligopithecidae share a mixture of traits that makes them difficult to classify more specifically within anthropoids. The best known member, <em>Catopithecus<\/em>, is known from crania that demonstrate a postorbital septum and from mandibles that lack symphyseal fusion. They share the catarrhine tooth formula of 2.1.2.3 and have a canine honing complex that involves the anterior lower premolar. The postcranial elements known for the group suggest generalized arboreal quadrupedalism. The best known member, <em>Catopithecus<\/em>, is known from crania that demonstrate a postorbital septum and from mandibles that lack symphyseal fusion (Simons and Rasmussen 1996). The jaws are deep, with broad muscle attachment areas and crested teeth. <em>Catopithecus<\/em> was probably a little less than a kilogram in weight.<\/p>\r\n<p class=\"import-Normal\">Other genera of putative anthropoids from the Fayum include the very poorly known <em>Arsinoea<\/em>, the contentious <em>Afrotarsius<\/em>, and the enigmatic <em>Nosmips<\/em>. The last of these possesses traits of several major primate <strong>[pb_glossary id=\"1705\"]clades[\/pb_glossary]<\/strong> and defies classification (Seiffert et al. 2010).<\/p>\r\n\r\n<h3 class=\"import-Normal\"><strong>Early Anthropoid Fossils in Asia<br style=\"clear: both\" \/><\/strong><\/h3>\r\n<p class=\"import-Normal\">For the last half of the 1900s, researchers believed that Africa was the unquestioned homeland of early anthropoids (see Fleagle and Kay 1994). However, two very different groups of primates from Asia soon began to change that. One was an entirely new discovery (Eosimiidae), and the other was a poorly known group discovered decades prior (Amphipithecidae). Soon, attention on anthropoid origins began to shift eastward (see Ross and Kay 2004; Simons 2004). If anthropoids arose in Asia instead of Africa, then this implies that the African early anthropoids either emigrated from Asia or evolved their anthropoid traits in parallel with living anthropoids.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Eosimiids<\/em><\/h4>\r\n<p class=\"import-Normal\">First described in the 1990s, the eosimiids are best represented by <em>Eosimias <\/em>(see Figure 9.14; Figure 9.18). This tiny \u201cdawn monkey\u201d is known from relatively complete jaws with teeth, a few small fragments of the face, and some postcranial elements (Beard et al. 1994; Beard et al. 1996; Gebo et al. 2000). <em>Eosimias<\/em> (along with the other less-well-known genera in its family) bears some resemblance to tarsiers as well as anthropoids. Unfortunately, no good crania are known for this family, and the anatomy of, for example, the posterior orbital margin could be very revealing as to higher-level relationships.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"550\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image16-1-1.jpg\" alt=\"Red-colored lower jaw of an animal.\" width=\"550\" height=\"232\" \/> Figure 9.18: Cast of the right half of the mandible of Eosimias centennicus, type specimen. The white scale bar is 1 cm long. Credit: <a class=\"rId74\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Cast of the right half of the mandible of <\/a><a class=\"rId75\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Eosimias centennicus <\/em><\/a><a class=\"rId76\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">(Figure 8.15),<\/a> type specimen, from K. D. Rose cast collection, photo by Jonathan M. G. Perry is under a <a class=\"rId77\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<h4 class=\"import-Normal\"><em>Amphipithecids<\/em><\/h4>\r\n<p class=\"import-Normal\">Amphipithecids are small- to medium-size primates (up to 10 kg; 22 lbs.). Most are from the Eocene Pondaung Formation in Myanmar (Early\u2013Middle Eocene), but one genus is known from Thailand. Some dental similarities with anthropoids were noted early on, such as deep jaws and wide basins that separate low molar cusps. The best known genera were <em>Pondaungia<\/em> and <em>Amphipithecus <\/em>(Ciochon and Gunnell 2002; see Figure 9.14). Another amphipithecid, <em>Siamopithecus<\/em> from Thailand, has very rounded molars and was probably a seed-eater (Figure 9.19). In addition to teeth and jaws, some cranial fragments, ankle material, and ends of postcranial bones have been found for <em>Pondaungia<\/em>. There are important resemblances between the postcranial bones of <em>Pondaungia<\/em> and those of adapoids, suggesting adapoid affinities for the amphipithecidae. This would imply that the resemblances with anthropoids in the teeth are convergent, based on similarities in diet (see Ciochon and Gunnell 2002). Unfortunately, the association between postcranial bones and teeth is not definite. With other primates in these faunas (including eosimiids), one cannot be certain that the postcranial bones belong with the teeth. Some researchers suggest that some bones belong to a sivaladapid (or asiadapid) and others to an early anthropoid (Beard et al. 2007; Marivaux et al. 2003). Additional well-associated material of amphipithecids would help to clear up this uncertainty.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"505\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image15-2.jpg\" alt=\"Four casts of jawbone fragments with teeth.\" width=\"505\" height=\"368\" \/> Figure 9.19: Casts of representative amphipithecid material. A. Pondaungia cotteri right lower jaw fragment with m2 and m3. B. Siamopithecus eocaenus right upper jaw fragment with p4-m3. C. S. eocaenus right lower jaw fragment with partial m1, m2, and m3 in lateral view. D. Same as in C but occlusal view. White scale bars are 1 cm long. Credit: <a class=\"rId79\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Casts of representative amphipithecid material (Figure 8.16)l<\/a> from K. D. Rose cast collection, photo by Jonathan M. G. Perry is under a <a class=\"rId80\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Platyrrhine Dispersal to South America<\/strong><\/h3>\r\n<p class=\"import-Normal\">Today there is an impressive diversity of primates in South and Central America. These are considered to be part of a single clade, the Platyrrhini. Primates colonized South America sometime in the Eocene from an African source. In the first half of the 20th century, the source of platyrrhines was a matter of major debate among paleontologists, with some favoring a North American origin (e.g., Simpson 1940).<\/p>\r\n<p class=\"import-Normal\">Part of the reason for this debate is that South America was an island in the Eocene. Primates needed to cross open ocean to get there from either North America or Africa, although the distance from the former was shorter. Morphology yields clues to platyrrhine origins. The first known primates in South America have more in common morphologically with African primates than with North American ones. At the time, anthropoids were popping up in North Africa, whereas the only euprimates in North America were adapoids and omomyoids. Despite lacking a bony ear tube, early platyrrhines shared a great deal with other anthropoids, including full postorbital closure and fusion of the mandibular symphysis.<\/p>\r\n<p class=\"import-Normal\">The means by which a population of small North African primates managed to disperse across the Atlantic and survive to colonize South America remains a mystery. The most plausible scenario is one of rafting. That is, primates must have been trapped on vegetation that was blown out to sea by a storm. The vegetation then became a sort of life raft, which eventually landed ashore, dumping its passengers in South America. Rodents probably arrived in South America in the same way (Antoine et al. 2012).<\/p>\r\n<p class=\"import-Normal\">Once ashore, platyrrhines must have crossed South America fairly rapidly because the earliest-known primates from that continent are from Peru (Bond et al. 2015). Soon after that, platyrrhines were in Bolivia, namely <em>Branisella<\/em>. By the Miocene, platyrrhines were living in extreme southern Argentina and were exploiting a variety of feeding niches. The Early Miocene platyrrhines were all somewhat plesiomorphic in their morphology, but some features that likely arose by ecological convergence suggest (to some) relationships with extant platyrrhine families. This has led to a lively debate about the pattern of primate evolution in South America (Kay 2015; Kay and Fleagle 2010; Rosenberger 2010). By the Middle Miocene, clear representatives of modern families were present in a diverse fauna from La Venta, Colombia (Wheeler 2010). The Plio-Pleistocene saw the emergence of giant platyrrhines as well as several taxa of platyrrhines living on Caribbean islands (Cooke et al. 2016).<\/p>\r\n<p class=\"import-Normal\">The story of platyrrhines seems to be one of amazing sweepstakes dispersal, followed by rapid diversification and widespread geographic colonization of much of South America. After that, dramatic extinctions resulted in the current, much-smaller geographic distribution of platyrrhines. These extinctions were probably caused by changing climates, leading to the contraction of forests. Platyrrhines dispersed to the Caribbean and to Central America, with subsequent extinctions in those regions that might have been related to interactions with humans. Unlike anthropoids of Africa and Asia, platyrrhines do not seem to have evolved any primarily terrestrial forms and so have always been highly dependent on forests.<\/p>\r\n\r\n<div class=\"textbox\">\r\n<h2 class=\"import-Normal\">Special Topic: Jonathan Perry and Primates of the Extreme South<\/h2>\r\n<p class=\"import-Normal\">Many primates are very vulnerable to ecological disturbance because they are heavily dependent on fruit to eat and trees to live in. This is one reason why so many primates are endangered today and why many of them went extinct due to climatic and vegetational changes in the past. I (Jonathan Perry) have conducted paleontological research focusing on primates that lived on the edge of their geographic distribution. This research has taken me to extreme environments in the Americas: southern Patagonia, the Canadian prairies, western Wyoming, and the badlands of eastern Oregon.<\/p>\r\n<p class=\"import-Normal\">Santa Cruz Province in Argentina is as far south as primates have ever lived. The Santa Cruz fauna of the Miocene has yielded a moderate diversity of platyrrhines, each with slightly different dietary adaptations. These include <em>Homunculus<\/em>, first described by Florentino Ameghino in 1891 (Figure 9.20). Recent fieldwork by my colleagues and I in Argentina has revealed several skulls of <em>Homunculus <\/em>as well as many parts of the skeleton (Kay et al. 2012). The emerging profile of this extinct primate is one of a dedicated arboreal quadruped that fed on fruits and leaves. Many of the foods eaten by <em>Homunculus<\/em> must have been very tough and were probably covered and impregnated with grit; we suspect this because the cheek teeth are very worn down, even in young individuals, and because the molar tooth roots were very large, presumably to resist strong bite forces (Perry et al. 2010, 2014).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"497\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image9-2.jpg\" alt=\"An animal skull, a partial skull, and a fossil jaw with teeth.\" width=\"497\" height=\"634\" \/> Figure 9.20: Representative specimens of Homunculus patagonicus. A. Adult cranium in lateral view. B. Adult cranium surface reconstructed from microCT scans, with the teeth segmented out. C. Juvenile cranium. White scale bars are 1cm long. Credit: <a class=\"rId82\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Representative specimens of <\/a><a class=\"rId83\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Homunculus patagonicus <\/em><\/a><a class=\"rId84\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">(Figure 8.17)<\/a> photo by Jonathan M. G. Perry is under a <a class=\"rId85\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n<p class=\"import-Normal\">I began working in Argentina while a graduate student at Duke University. I participated as a field assistant in a team led by my Ph.D. advisor, Richard F. Kay, and Argentine colleagues Sergio F. Vizca\u00edno and M. Susana Bargo. Most of the localities examined belong to a suite of beach sites known since the 1800s and visited by many field parties from various museums in the early 1900s. Since 2003, our international team of paleontologists from the U.S. and Argentina has visited these localities every single year (Figure 9.21). Over time, new fossils and new students have led to new projects and new approaches, including the use of microcomputed tomography (microCT) to visualize and analyze internal structures of the skeleton.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"491\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image23.jpg\" alt=\"Sandy rocky coastline. People digging on a grassy hillside.\" width=\"491\" height=\"561\" \/> Figure 9.21: Field localities in Argentina and Canada. A. Ca\u00f1adon Palos locality, coastal Santa Cruz Province, Argentina. B. Swift Current Creek locality, southwest Saskatchewan, Canada. Credits: A. <a class=\"rId87\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Ca\u00f1adon Palos Field Locality in Argentina<\/a> by Jonathan M. G. Perry is under a <a class=\"rId88\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. B. <a class=\"rId89\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Swift Current Creek locality, Saskatchewan, Canada<\/a> by Jonathan M. G. Perry is under a <a class=\"rId90\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.[\/caption]\r\n\r\n<\/div>\r\n<h2 class=\"import-Normal\">Planet of Apes<\/h2>\r\n<h3 class=\"import-Normal\"><strong>Geologic Activity and Climate Change in the Miocene<\/strong><\/h3>\r\n<p class=\"import-Normal\">The Miocene Epoch was a time of mammalian diversification and extinction, global climate change, and ecological turnover. In the Miocene, there was an initial warming trend across the globe with the expansion of subtropical forests, followed by widespread cooling and drying with the retreat of tropical forests and replacement with more open woodlands and eventually grasslands. It was also a time of major geologic activity. On one side of the globe, South America experienced the rise of the Andes Mountains. On the other side, the Indian subcontinent collided with mainland Asia, resulting in the rise of the Himalayan Mountains. In Africa, volcanic activity promoted the development of the East African Rift System. Critical to the story of ape evolution was the exposure of an intercontinental landbridge between East Africa and Eurasia, permitting a true planet of apes (Figure 9.22).<\/p>\r\n\r\n\r\n[caption id=\"attachment_277\" align=\"aligncenter\" width=\"580\"]<img class=\"wp-image-273\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image21-3-e1691792198797.png\" alt=\"Map of world with gray continents.\" width=\"580\" height=\"335\" \/> Figure 9.22: Map of the world in the Miocene, highlighting fossil ape localities across Africa, southern Europe, and southern Asia. Credit: <a class=\"rId92\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Miocene Map with Fossil Ape Localities (Figure 8.19)<\/a> original to <a class=\"rId93\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId94\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId95\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 311.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Geographic Distribution: Africa, Asia, Europe<\/strong><\/h3>\r\n<p class=\"import-Normal\">The world of the Miocene had tremendous ape diversity compared to today. The earliest records of fossil apes are from Early Miocene deposits in Africa. However, something dramatic happened around 16 million years ago. With the closure of the ancient Tethys Sea, the subsequent exposure of the <em>Gomphotherium<\/em> Landbridge, and a period of global warming, the Middle\u2013Late Miocene saw waves of emigration of mammals (including primates) out of Africa and into Eurasia, with evidence of later African re-entry for some (Harrison 2010). Some of the mammals that dispersed from Africa to Eurasia and back were apes. Though most of these early apes left no modern descendants, some of them gave rise to the ancestors of modern apes\u2014including <strong>[pb_glossary id=\"800\"]hominins[\/pb_glossary]<\/strong> (Figure 9.23).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"560\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image20-1.jpg\" alt=\"Miocene apes set against a geologic time scale.\" width=\"560\" height=\"796\" \/> Figure 9.23: Representative Miocene apes set against a geologic time scale. Credit: <a href=\"https:\/\/www.pnas.org\/content\/108\/14\/5554\">Range chart for Miocene hominoids of Western Eurasia (Figure 3)<\/a> by Isaac Casanovas-Vilar, David M. Alba, Miguel Garc\u00e9s, Josep M. Robles, and Salvador Moy\u00e0-Sol\u00e0. 2011. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America<\/a> 108 (14): 5554-5559. Copyright (2011) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a>[\/caption]\r\n<h3 class=\"import-Normal\"><strong>Where Are the Monkeys? Diversity in the Miocene<\/strong><\/h3>\r\n<p class=\"import-Normal\">Whereas the Oligocene deposits in the Fayum of Egypt have yielded the earliest-known catarrhine fossils, the Miocene demonstrates some diversification of Cercopithecoidea. However, compared to the numerous and diverse Miocene apes (see below), monkeys of the Miocene are very rare and restricted to a single extinct family, the Victoriapithecidae (Figure 9.24). This family contains the earliest definite cercopithecoids. These monkeys are found from northern and eastern Africa between 20 million and 12.5 million years ago (Miller et al. 2009). The best known early African monkey is <em>Victoriapithecus <\/em>(Figure 9.25), a small-bodied (approximately 7 kg; 15 lbs.), small-brained monkey. <strong>[pb_glossary id=\"1708\"]Bilophodonty[\/pb_glossary]<\/strong>, known to be a hallmark of molar teeth of modern cercopithecoid, was present to some extent in Victoriapithecids. <em>Victoriapithecus<\/em> has been reconstructed as being more frugivorous and perhaps spent more time on the ground (terrestrial locomotion) than in the trees (arboreal locomotion; Blue et al. 2006). The two major groups of cercopithecoids today are cercopithecines and colobines. The earliest records demonstrating clear members of each of these two groups are at the end of the Miocene. Examples include the early colobine <em>Microcolobus<\/em> from Kenya and the early cercopithecine <em>Pliopapio<\/em> from Ethiopia.<\/p>\r\n\r\n<div style=\"text-align: left\">\r\n<table class=\"aligncenter\" style=\"width: 473.25pt;height: 349px\"><caption>Figure 9.24: Some families of later anthropoids with example genera and traits: a table. Credit: Late anthropoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId100\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\r\n<thead>\r\n<tr style=\"height: 25pt\">\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 119.35px\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 103.417px\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 191.65px\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 67.3667px\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\r\n&nbsp;<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 73.2167px\">\r\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\r\n&nbsp;<\/td>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr class=\"Table4-R\" style=\"height: 18pt\">\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 119.35px\">\r\n<p class=\"import-Normal\">Victoriapithecidae<sup>2<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 103.417px\">\r\n<p class=\"import-Normal\"><em>Victoriapithecus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 191.65px\">\r\n<p class=\"import-Normal\">Long, sloping face. Round, narrowly spaced orbits. Deep cheek bones. Well-developed sagittal crest.<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 67.3667px\">\r\n<p class=\"import-Normal\">Africa<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 73.2167px\">\r\n<p class=\"import-Normal\">Early to Middle Miocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table4-R\" style=\"height: 16pt\">\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 119.35px\">\r\n<p class=\"import-Normal\">Proconsulidae<sup>3<\/sup><\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 103.417px\">\r\n<p class=\"import-Normal\"><em>Proconsul<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 191.65px\">\r\n<p class=\"import-Normal\">Short face. Generalized dentition. Arboreal quadruped. Probably tailless.<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 67.3667px\">\r\n<p class=\"import-Normal\">Africa and Arabia<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 73.2167px\">\r\n<p class=\"import-Normal\">Early to Middle Miocene<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table4-R\" style=\"height: 16pt\">\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 119.35px\">\r\n<p class=\"import-Normal\">Pongidae<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 103.417px\">\r\n<p class=\"import-Normal\"><em>Gigantopithecus<\/em><\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 191.65px\">\r\n<p class=\"import-Normal\">Largest primate ever. Deep jaws and low rounded molars.<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 67.3667px\">\r\n<p class=\"import-Normal\">Asia<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 73.2167px\">\r\n<p class=\"import-Normal\">Miocene to Present<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"Table4-R\" style=\"height: 1pt\">\r\n<td class=\"Table4-C\" style=\"border-color: #000000;border-style: solid none none;border-width: 0.5pt 0pt 0pt;padding: 0pt 5.4pt;height: 90px;width: 526.983px\" colspan=\"4\">\r\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\r\n<p class=\"import-Normal\"><sup>2<\/sup> See Benefit and McCrossin 1997 and Fleagle 2013.<\/p>\r\n<p class=\"import-Normal\"><sup>3<\/sup> See Begun 2007.<\/p>\r\n<\/td>\r\n<td class=\"Table4-C\" style=\"border-color: #000000;border-style: solid none none;border-width: 0.5pt 0pt 0pt;padding: 0pt 5.4pt;height: 90px;width: 73.2167px\">\r\n<p class=\"import-Normal\"><\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr style=\"height: 15px\">\r\n<td style=\"height: 15px;width: 121.283px\"><\/td>\r\n<td style=\"height: 15px;width: 105.35px\"><\/td>\r\n<td style=\"height: 15px;width: 193.583px\"><\/td>\r\n<td style=\"height: 15px;width: 69.3px\"><\/td>\r\n<td style=\"height: 15px;width: 74.65px\"><\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3 class=\"import-Normal\"><strong>The Story of Us, the Apes<\/strong><\/h3>\r\n<h4 class=\"import-Normal\"><em>African Ape Diversity\u00a0<\/em><\/h4>\r\n<p class=\"import-Normal\">The Early Miocene of Africa has yielded around 14 genera of early apes (Begun 2003). Many of these taxa have been reconstructed as frugivorous arboreal quadrupeds (Kay 1977). One of the best studied of these genera is the East African <em>Proconsul<\/em> (Family Proconsulidae; see Figure 9.24). Several species have been described, with body mass reconstructions ranging from 17 to 50 kg (approximately 37\u2013110 lbs.). A paleoenvironmental study reconstructed the habitat of <em>Proconsul <\/em>to be a dense, closed-canopy tropical forest (Michel et al. 2014). No caudal vertebrae (tail bones) have been found in direct association with <em>Proconsul <\/em>postcrania, and the morphology of the sacrum is consistent with <em>Proconsul<\/em> lacking a tail (Russo 2016; Ward et al. 1991).<\/p>\r\n<p class=\"import-Normal\">Overall, the African ape fossil record in the Late Miocene is sparse, with seven fossil localities dating between eleven and five million years ago (Pickford et al. 2009). Nevertheless, most species of great apes live in Africa today. Where did the progenitors of modern African apes arise? Did they evolve in Africa or somewhere else? The paucity of apes in the Late Miocene of Africa stands in contrast to the situation in Eurasia. There, ape diversity was high. Furthermore, several Eurasian ape fossils show morphological affinities with modern hominoids (apes). Because of this, some paleoanthropologists suggest that the ancestors of modern African great apes recolonized Africa from Eurasia toward the end of the Miocene (Begun 2002). However, discoveries of Late Miocene hominoids like the Kenyan <em>Nakalipithecus<\/em> (9.9 million to 9.8 million years ago), the Ethiopian <em>Chororapithecus<\/em> (10.7 million to 10.1 million years ago), and the late-Middle Miocene Namibian <em>Otavipithecus<\/em> (13 million to 12 million years ago) fuel an alternative hypothesis\u2014namely that African hominoid diversity was maintained throughout the Miocene and that one of these taxa might, in fact, be the last common ancestor of extant African apes (Kunimatsu et al. 2007; Mocke et al. 2002). The previously underappreciated diversity of Late Miocene apes in Africa might be due to poor sampling of the fossil record in Africa.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Eurasian Ape Diversity<\/em><\/h4>\r\n<p class=\"import-Normal\">With the establishment of the <em>Gomphotherium<\/em> Landbridge (a result of the closure of the Eastern Mediterranean seaway; R\u00f6gl 1999), the Middle Miocene was an exciting time for hominoid radiations outside of Africa (see Figure 9.23). Eurasian hominoid species exploited their environments in many different ways in the Miocene. Food exploitation ranged from soft-fruit feeding in some taxa to hard-object feeding in others, in part owing to seasonal fluctuations and the necessary adoptions of fallback foods (DeMiguel et al. 2014). For example, the molars of <em>Oreopithecus bambolii<\/em> (Family Hominidae) have relatively long lower-molar shearing crests, suggesting that this hominoid was very folivorous (Ungar and Kay 1995). Associated with variation in diet, there is great variation in the degree to which cranial features (e.g., zygomatic bone or supraorbital tori) are developed across the many taxa (Cameron 1997); however, Middle Miocene fossils tend to exhibit relatively thick molar enamel and relatively robust jaws (Andrews and Martin 1991).<\/p>\r\n<p class=\"import-Normal\">In Spain, the cranium with upper dentition, part of a mandible, and partial skeleton of <em>Pliobates <\/em>(Family Pliobatidae), a small-bodied ape (4\u20135 kg; 9\u201311 lbs.), was discovered in deposits dating to 11.6 million years ago (Alba et al. 2015). It is believed to be a frugivore with a relative brain size that overlaps with modern cercopithecoids. The fossilized postcrania of <em>Pliobates<\/em> suggest that this ape might have had a unique style of locomotion, including the tendency to walk across the branches of trees with its palms facing downward and flexible wrists that permitted rotation of the forearm during climbing. However, the anatomy of the distal humerus differs from those of living apes in ways that suggest that <em>Pliobates<\/em> was less efficient at stabilizing its elbow while suspended (Benefit and McCrossin 2015). Two other recently described apes from Spain, <em>Pierolapithecus <\/em>and <em>Anoiapithecus<\/em>, are known from relatively complete skeletons. <em>Pierolapithecus<\/em> had a very projecting face and thick molar enamel as well as some skeletal features that suggest (albeit controversially) a less suspensory locomotor style than in extant apes (Moy\u00e0-Sol\u00e0 et al. 2004). In contrast to <em>Pierolapithecus<\/em>, the slightly younger <em>Anoiapithecus<\/em> has a very flat face (Moy\u00e0-Sol\u00e0 et al. 2009).<\/p>\r\n<p class=\"import-Normal\">Postcranial evidence for suspensory or well-developed orthograde behaviors in apes does not appear until the Late Miocene of Europe. Primary evidence supporting these specialized locomotor modes includes the relatively short lumbar vertebrae of <em>Oreopithecus <\/em>(Figure 9.26) and <em>Dryopithecus<\/em> (Maclatchy 2004). Further, fossil material of the lower torso of <em>O. bambolii <\/em>(which dates to the <em>Pan<\/em>-hominin divergence) conveys a higher degree of flexion-extension abilities in the lumbar region (lower back) than what is possible in extant apes. Additionally, the hindlimb of <em>O. bambolii <\/em>is suggested to have supported powerful hip adduction during climbing (Hammond et al. 2020). The Late Miocene saw the extinction of most of the Eurasian hominoids in an event referred to as the Vallesian Crisis (Agust\u00ed et al. 2003). Among the latest surviving hominoid taxa in Eurasia were <em>Oreopithecus<\/em> and <em>Gigantopithecus<\/em>, the latter of which held out until the Pleistocene in Asia and was probably even sympatric with <em>Homo erectus<\/em> (Cachel 2015).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"436\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image8-2-1.jpg\" alt=\"Posterior view of ancient ape skeleton.\" width=\"436\" height=\"775\" \/> Figure 9.26: Skeleton of Oreopithecus bambolii. Credit: <a class=\"rId107\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Oreopithecus_bambolii_1.JPG\">Oreopithecus bambolii 1<\/a> by <a class=\"rId108\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Ghedoghedo\">Ghedoghedo<\/a> is under a <a class=\"rId109\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/legalcode\">CC BY-SA 3.0 License<\/a>.[\/caption]\r\n<h3 class=\"import-Normal\"><strong>The Origins of Extant Apes<\/strong><\/h3>\r\n<p class=\"import-Normal\">The fossil record of the extant apes is somewhat underwhelming: it ranges from being practically nonexistent for some taxa (e.g., chimpanzees) to being a little better for others (e.g., humans). There are many possible reasons for these differences in fossil abundance, and many are associated with the environmental conditions necessary for the fossilization of bones. One way to understand the evolution of extant apes that is not so dependent on the fossil record is via molecular evolutionary analyses. This can include counting up the differences in the genetic sequence between two closely related species to estimate the amount of time since these species shared a common ancestor. This is called a molecular clock, and it is often calibrated using fossils of known absolute age that stand in for the last common ancestor of a particular clade. Molecular clock estimates have placed the Hylobatidae and Hominidae split between 19.7 million and 24.1 million years ago, the African ape and Asian ape split between 15.7 million and 19.3 million years ago, and the split of Hylobatidae into its current genera between 6.4 million and 8 million years ago (Israfil et al. 2011).<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Small Ape Origins and Fossils<\/em><\/h4>\r\n<p class=\"import-Normal\">Unfortunately, the fossil record for the small (formerly \u201clesser\u201d) apes is meager, particularly in Miocene deposits. One possible early hylobatid is <em>Laccopithecus robustus<\/em>, a Late Miocene catarrhine from China (Harrison 2016). Although it does share some characteristics with modern gibbons and siamangs (including an overall small body size and a short face), <em>Laccopithecus<\/em> most likely represents a plesiomorphic stem catarrhine and is therefore distantly related to extant apes (Jablonski and Chaplin 2009). A more likely candidate for the hylobatid stem is another Late Miocene taxon from China, <em>Yuanmoupithecus xiaoyuan<\/em>. Interpretation of its phylogenetic standing, however, is complicated by contradicting dental features\u2014some of them quite plesiomorphic\u2014which some believe best place <em>Yuanmoupithecus<\/em> as a stem hylobatid (Harrison 2016). Recently, a Middle Miocene Indian fossil ape, <em>Kapi ramnagarensis<\/em>, has extended the fossil record of small apes by approximately five million years. Its teeth are suggestive of a shift to a more frugivorous diet and it is likely a stem hylobatid (Gilbert et al. 2020). The history of Hylobatidae becomes clearer in the Pleistocene, with fossils representing extant genera.<\/p>\r\n\r\n<h4 class=\"import-Normal\"><em>Great Ape Origins and Fossils<\/em><\/h4>\r\n<p class=\"import-Normal\">The most extensive fossil record of a modern great ape is that of our own genus, <em>Homo<\/em>. However, the evolutionary history of the Asian great ape, the orangutan (<em>Pongo<\/em>), is becoming clearer. Today, orangutans are found only on the islands of Borneo and Sumatra. However, Pleistocene-aged teeth, attributed to <em>Pongo<\/em>, have been found in Cambodia, China, Laos, Peninsular Malaysia, and Vietnam\u2014demonstrating the vastness of the orangutan\u2019s previous range (Ibrahim et al. 2013; Wang et al. 2014). <em>Sivapithecus <\/em>from the Miocene of India and Pakistan is represented by many specimens, including parts of the face. <em>Sivapithecus<\/em> is very similar to <em>Pongo<\/em>, especially in the face, and it probably is closely related to ancestral orangutans (Pilbeam 1982). Originally, jaws and teeth belonging to the former genus <em>Ramapithecus<\/em> were thought to be important in the origin of humans (Simons 1961), but now these are recognized as specimens of <em>Sivapithecus<\/em> (Kelley 2002). Postcranial bones of <em>Sivapithecus<\/em>, however, suggest a more generalized locomotor mode\u2014including terrestrial locomotion\u2014than seen in <em>Pongo <\/em>(Pilbeam et al. 1990). Stable carbon and oxygen isotope data from dental enamel have reconstructed the paleoecological space of <em>Sivapithecus <\/em>(as well as the contemporaneous Late Miocene pongine <em>Khoratpithecus<\/em>) within the canopies of forested habitats (Habinger et al. 2022).<\/p>\r\n<p class=\"import-Normal\">A probable close relative of <em>Sivapithecus <\/em>is the amazing <em>Gigantopithecus<\/em> (see Figure 9.24). Known only from teeth and jaws from China and India (e.g., Figure 9.27), this ape probably weighed as much as 270 kg (595 lbs.) and was likely the largest primate ever (Bocherens et al. 2017). Because of unique features of its teeth (including molarized premolars and patterns of wear) and its massive size, it has been reconstructed as a bamboo specialist, somewhat like the modern panda. Small silica particles (phytoliths) from grasses have been found stuck to the molars of <em>Gigantopithecus<\/em> (Ciochon et al. 1990). Recent studies evaluating the carbon isotope composition of the enamel sampled from <em>Gigantopithecus<\/em> teeth suggest that this ape exploited a wide range of vegetation, including fruits, leaves, roots, and bamboo (Bocherens et al. 2017). Its face is reminiscent of that of modern orangutans and it might belong in the same family, Pongidae (Kelley 2002).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"488\"]<img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image12.jpg\" alt=\"Superior view of mandible and teeth.\" width=\"488\" height=\"533\" \/> Figure 9.27: Cast of the mandible of Gigantopithecus blacki. Credit: <a class=\"rId111\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Gigantopithecus%20blacki%20mandible%20010112.jpg\">Gigantopithecus blacki mandible 010112<\/a> by <a class=\"rId112\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Wilson44691\">Wilson44691<\/a> is under a <a class=\"rId113\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/legalcode\">CC BY-SA 3.0 License<\/a>.[\/caption]\r\n<p class=\"import-Normal\">In Africa, the first fossil to be confidently attributed to <em>Pan<\/em>, and known to be the earliest evidence of a chimpanzee, was described based on teeth found in Middle Pleistocene deposits in the Eastern Rift Valley of Kenya (McBrearty and Jablonski 2005). Paleoenvironmental reconstructions of this locality suggest that this early chimpanzee was living in close proximity to early <em>Homo<\/em> in a closed-canopy wooded habitat. Similarly, fossil teeth and mandibular remains attributed to two species of Middle-Late Miocene apes\u2014<em>Chororapithecus abyssinicus<\/em> (from Ethiopia; Suwa et al. 2007) and <em>Nakalipithecus nakayamai<\/em> (from Kenya; Kunimatsu et al. 2007)\u2014have been suggested as basal members of the gorilla clade.<\/p>\r\n<p class=\"import-Normal\">While the deposits of Eastern Africa have yielded a profound record of our fossil hominin ancestors, the continent\u2019s rainforests remain a \u201cpalaeontological desert\u201d (Rosas et al. 2022). Clearly, more work is needed to fill in the large gaps in the fossil record of the nonhuman great apes. The twentieth century witnessed the discovery of many hominin fossils in East Africa, which have been critical for improving our understanding of human evolution. While twenty-first-century conservationists fight to prevent the extinction of the living great apes, perhaps efforts by twenty-first-century paleoanthropologists will yield the evolutionary story of these, our closest relatives.<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<h2>Summary<\/h2>\r\nWhile there are large gaps in the fossil records linking primates to early hominins, evolutionary trends make it clear that humans are one branch of the broader primate family tree. In this chapter we go over the major development that characterize primate evolution: enhanced vision, grasping hands and feet, greater reliance on social behavior, and increased brain complexity. It is these traits which distinguish primates from other mammals and furthermore, help define major subsections within the primate class, such as strepsirrhines, haplorhines, monkeys, apes, and ultimately hominins.\r\n\r\nWithin this chapter, we also examine how anthropologists reconstruct these evolutionary relationships. Fossil evidence has provided key information about when and where different primates lived, while genetic data such as skeletal features allow researchers to understand how extinct species moved, ate, and interacted with their environments. Just as crucial are the influences of Earth\u2019s changing environments: continental drift, glacial cycles, and long-term climate shifts have repeatedly reshaped habitats, driving both extinctions and the emergence of new adaptive forms, including the emergence of our own human lineage.\r\n<h2 class=\"import-Normal\">Review Questions<strong>\r\n<\/strong><\/h2>\r\n<ul>\r\n \t<li>Compare three major hypotheses about primate origins, making reference to each one\u2019s key ecological reason for primate uniqueness.<\/li>\r\n \t<li>Explain how changes in temperature, rainfall, and vegetation led to major changes in primate biogeography over the Early Tertiary.<\/li>\r\n \t<li>List some euprimate features that plesiadapiforms have and some that they lack.<\/li>\r\n \t<li>Contrast adapoids and omomyoids in terms of life habits.<\/li>\r\n \t<li>Describe one piece of evidence for each of the adapoid, omomyoid, and tarsier origin hypotheses for anthropoids.<\/li>\r\n \t<li>Discuss the biogeography of the origins of African great apes and orangutans using examples from the Miocene ape fossil record.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<h2 class=\"import-Normal\">Key Terms<strong>\r\n<\/strong><\/h2>\r\n<p class=\"import-Normal\"><strong>Adapoidea<\/strong>: Order: Primates. One of the earliest groups of euprimates (true primates; earliest records from the early Eocene).<\/p>\r\n<p class=\"import-Normal\"><strong>A<\/strong><strong>daptive radiations<\/strong>: Rapid diversifications of single lineages into many species which may present unique morphological features in response to different ecological settings.<\/p>\r\n<p class=\"import-Normal\"><strong>Ancestral traits<\/strong>: Features that were inherited from a common ancestor and which remain (largely) unchanged.<\/p>\r\n<p class=\"import-Normal\"><strong>Anthropoids<\/strong>:Group containing monkeys and apes, including humans.<\/p>\r\n<p class=\"import-Normal\"><strong>Auditory bulla<\/strong>: The rounded bony floor of the middle ear cavity.<\/p>\r\n<p class=\"import-Normal\"><strong>Bilophodonty<\/strong>: Dental condition in which the cusps of molar teeth form ridges (or lophs) separated from each other by valleys (seen, e.g., in modern catarrhine monkeys).<\/p>\r\n<p class=\"import-Normal\"><strong>Catarrhines<\/strong>: Order: Primates; Suborder: Anthropoidea; Infraorder: Catarrhini. Group, with origins in Africa and Asia, that contains monkeys and apes, including humans.<\/p>\r\n<p class=\"import-Normal\"><strong>Clade<\/strong>:Group containing all of the descendants of a single ancestor. A portion of a phylogenetic tree represented as a bifurcation (node) in a lineage and all of the branches leading forward in time from that bifurcation.<\/p>\r\n<p class=\"import-Normal\"><strong>Convergent evolution<\/strong>: The independent evolution of a morphological feature in animals not closely related (e.g., wings in birds and bats).<\/p>\r\n<p class=\"import-Normal\"><strong>Crown<\/strong>: Smallest monophyletic group (clade) containing a specified set of extant taxa and all descendants of their last common ancestor.<\/p>\r\n<p class=\"import-Normal\"><strong>Diastema<\/strong>: Space between adjacent teeth.<\/p>\r\n<p class=\"import-Normal\"><strong>Diffuse coevolution<\/strong>: The ecological interaction between whole groups of species (e.g., primates) with whole groups of other species (e.g., fruiting trees).<\/p>\r\n<p class=\"import-Normal\"><strong>Ectotympanic<\/strong>: Bony ring or tube that holds the tympanic membrane (eardrum).<\/p>\r\n<p class=\"import-Normal\"><strong>Euprimates<\/strong>: Order: Primates. True primates or primates of modern aspect.<\/p>\r\n<p class=\"import-Normal\"><strong>Haplorhines<\/strong>: Group containing catarrhines, platyrrhines, and tarsiers.<\/p>\r\n<p class=\"import-Normal\"><strong>Hominins<\/strong>: Modern humans and any extinct relatives more closely related to us than to chimpanzees.<\/p>\r\n<p class=\"import-Normal\"><strong>Mandibular symphysis<\/strong>: Fibrocartilaginous joint between the left and right mandibular segments, located in the midline of the body.<\/p>\r\n<p class=\"import-Normal\"><strong>Omomyoidea<\/strong>: Order: Primates; Superfamily: Omomyoidea. One of the earliest groups of euprimates (true primates; earliest record in the early Eocene).<\/p>\r\n<p class=\"import-Normal\"><strong>Petrosal bone<\/strong>: The portion of the temporal bone that houses the inner ear apparatus.<\/p>\r\n<p class=\"import-Normal\"><strong>Plagiaulacoid<\/strong>: Dental condition where at least one of the lower cheek-teeth (molars or premolars) is a laterally compressed blade.<\/p>\r\n<p class=\"import-Normal\"><strong>Platyrrhines<\/strong>: Order: Primates; Suborder: Anthropoidea; Infraorder: Platyrrhini. Group containing monkeys found in the Americas.<\/p>\r\n<p class=\"import-Normal\"><strong>Plesiadapiforms<\/strong>: Order: Plesiadapiformes. Archaic primates or primate-like placental mammals (Early Paleocene\u2013Late Eocene).<\/p>\r\n<p class=\"import-Normal\"><strong>P<\/strong><strong>lesiomorphic<\/strong>: Having features that are shared by different groups which arose from a common ancestor.<\/p>\r\n<p class=\"import-Normal\"><strong>Stem<\/strong>: Taxa that are basal to a given crown group but are more closely related to the crown group than to the closest living sister taxon of the crown group.<\/p>\r\n<p class=\"import-Normal\"><strong>Strepsirrhines<\/strong>: Order: Primates; Suborder: Stresirrhini. Group containing lemurs, lorises, and galagos (does not include tarsiers).<\/p>\r\n<p class=\"import-Normal\"><strong>Toothcomb<\/strong>: Dental condition found in modern strepsirrhines in which the lower incisors and canines are laterally compressed and protrude forward at a nearly horizontal inclination. This structure is used in grooming.<\/p>\r\n\r\n<\/div>\r\n<div class=\"__UNKNOWN__\">\r\n<h2 class=\"import-Normal\">For Further Exploration<strong>\r\n<\/strong><\/h2>\r\n<p class=\"import-Normal\">Beard, Chris. 2004. <em>The Hunt for the Dawn Monkey: Unearthing the Origins of Monkeys, Apes, and Humans<\/em>. Berkeley: University of California Press.<\/p>\r\n<p class=\"import-Normal\">Begun, David R. 2010. \u201cMiocene Hominids and the Origins of the African Apes and Humans.\u201d <em>Annual Review of Anthropology<\/em> 39: 67\u201384.<\/p>\r\n<p class=\"import-Normal\">Fleagle, John G. 2013. <em>Primate Adaptation and Evolution.<\/em> Third edition. San Diego, CA: Academic Press.<\/p>\r\n<p class=\"import-Normal\">Gebo, Daniel L., ed. 1993. <em>Postcranial Adaptations in Nonhuman Primates<\/em>. Dekalb: Northern Illinois University Press.<\/p>\r\n<p class=\"import-Normal\">Godfrey, Laurie R., and William L. Jungers. 2002. \u201cQuaternary Fossil Lemurs.\u201d In <em>The Primate Fossil Record, <\/em>edited by Walter C. Hartwig, 97\u2013121. Cambridge: Cambridge University Press.<\/p>\r\n<p class=\"import-Normal\">Godinot, Marc. 2006. \u201cLemuriform Origins as Viewed from the Fossil Record.\u201d <em>Folia Primatologica<\/em> 77 (6): 446\u2013464.<\/p>\r\n<p class=\"import-Normal\">Kay, Richard F. 2018. \u201c100 Years of Primate Paleontology.\u201d <em>American Journal of Physical Anthropology<\/em> 165 (4): 652\u2013676.<\/p>\r\n<p class=\"import-Normal\">Marivaux, Laurent. 2006. \u201cThe Eosimiid and Amphipithecid Primates (Anthropoidea) from the Oligocene of the Bugti Hills (Balochistan, Pakistan): New Insight into Early Higher Primate Evolution in South Asia.\u201d <em>Palaeovertebrata, Montpellier <\/em>34 (1\u20132): 29\u2013109.<\/p>\r\n<p class=\"import-Normal\">Martin, R. D. 1990. <em>Primate Origins and Evolution<\/em><em>: A <\/em><em>Phylogenetic Reconstruction<\/em>. Princeton: Princeton University Press.<\/p>\r\n<p class=\"import-Normal\">Rose, Kenneth D., Marc Godinot, and Thomas M. Bown. 1994. \u201cThe Early Radiation of Euprimates and the Initial Diversification of Omomyidae.\u201d In <em>Anthropoid Origins: The Fossil Evidence, <\/em>edited by John G. Fleagle and Richard F. Kay, 1\u201328. New York: Plenum Press.<\/p>\r\n<p class=\"import-Normal\">Ross, Callum F. 1999. \u201cHow to Carry Out Functional Morphology.\u201d <em>Evolutionary Anthropology<\/em> 7 (6): 217\u2013222.<\/p>\r\n<p class=\"import-Normal\">Seiffert, Erik R. 2012. \u201cEarly Primate Evolution in Afro-Arabia.\u201d Evolutionary Anthropology: Issues, News, and Reviews 21(6): 239\u2013253.<\/p>\r\n<p class=\"import-Normal\">Szalay, Frederic S., and Eric Delson. 1979. Evolutionary History of the Primates. New York: Academic Press.<\/p>\r\n<p class=\"import-Normal\">Ungar, Peter S. 2002. \u201cReconstructing the Diets of Fossil Primates.\u201d In <em>Reconstructing Behavior in the Primate Fossil Record<\/em>, edited by Joseph Plavcan, Richard F. Kay, William Jungers, and Carel P. van Schaik, 261\u2013296. New York: Kluwer Academic\/Plenum Publishers.<\/p>\r\n\r\n<h2 class=\"import-Normal\">References<\/h2>\r\n<p class=\"import-Normal\">Agust\u00ed, J., A. Sanz de Siria, and M. Garc\u00e9s M. 2003. \u201cExplaining the End of the Hominoid Experiment in Europe.\u201d <em>Journal of Human Evolution<\/em> 45 (2): 145\u2013153.<\/p>\r\n<p class=\"import-Normal\">Alba, David M., Sergio Alm\u00e9cija, Daniel DeMiguel, Josep Fortuny, Miriam P\u00e9rez de los R\u00edos, Marta Pina, Josep M. 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Christopher, Laurent Marivaux, Soe Thura Tun, Aung Naing Soe, Yaowalak Chaimanee, Wanna Htoon, Bernard Marandat, Htun Htun Aung, and Jean-Jacques Jaeger. 2007. \u201cNew Sivaladapid Primates from the Eocene Pondaung Formation of Myanmar and the Anthropoid Status of Amphipithecidae.\u201d <em>Bulletin of Carnegie Museum of Natural History<\/em> 39: 67\u201376.<\/p>\r\n<p class=\"import-Normal\">Beard, K. Christopher, Tao Qi, Mary R. Dawson, Banyue Wang, and Chuankuei Li. 1994. \u201cA Diverse New Primate Fauna from Middle Eocene Fissure-Fillings in Southeastern China.\u201d <em>Nature<\/em> 368 (6472): 604\u2013609.<\/p>\r\n<p class=\"import-Normal\">Beard, K. Christopher, Yongsheng Tong, Mary R. 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New York: Kluwer\/Plenum Publishing.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L. 1961. \u201cThe Phyletic Position of <em>Ramapithecus<\/em>.\u201d <em>Postilla<\/em> 57: 1\u20139.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L. 2001. \u201cThe Cranium of <em>Parapithecus grangeri<\/em>, an Egyptian Oligocene Anthropoidean Primate.\u201d <em>Proceedings of the National Academy of Sciences of the United States of America<\/em> 98 (4): 7892\u20137897.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L. 2004. \u201cThe Cranium and Adaptations of <em>Parapithecus grangeri<\/em>, a Stem Anthropoid From the Fayum Oligocene of Egypt.\u201d In <em>Anthropoid Origins: New Visions<\/em>, edited by Callum F. Ross and Richard F. Kay, 183\u2013204. New York: Kluwer\/Plenum Publishing.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L. 2008. \u201cEocene and Oligocene Mammals of the Fayum, Egypt.\u201d In <em>Elwyn Simons: A Search for Origins<\/em>, edited by John G. Fleagle and Christopher C. Gilbert, 87\u2013105. New York: Springer.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L., and D. Tab Rasmussen. 1994a. \u201cA Remarkable Cranium of <em>Plesiopithecus teras<\/em> (Primates, Prosimii) from the Eocene of Egypt.\u201d <em>Proceedings of the National Academy of Sciences<\/em> <em>of the United States of America<\/em> 91(21): 9946\u20139950.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L., and D. Tab Rasmussen. 1994b. \u201cA Whole New World of Ancestors: Eocene Anthropoideans from Africa.\u201d <em>Evolutionary Anthropology<\/em> 3 (4): 128\u2013139.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L., and D. Tab Rasmussen. 1996. \u201cSkull of <em>Catopithecus browni<\/em>, an Early Tertiary Catarrhine.\u201d <em>American Journal of Physical Anthropology<\/em> 100 (2): 261\u2013292.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L., and Erik R. Seiffert. 1999. \u201cA Partial Skeleton of <em>Proteopithecus<\/em> <em>sylviae<\/em> (Primates Anthropoidea): First Associated Dental and Postcranial Remains of an Eocene Anthropoidean.\u201d <em>Comptes Rendus de l'Acad\u00e9mie des Sciences, Paris<\/em> 329 (12): 921\u2013927.<\/p>\r\n<p class=\"import-Normal\">Simons, Elwyn L., Erik R. Seiffert, Timothy M. Ryan, and Yousry Attia. 2007. \u201cA Remarkable Female Cranium of the Early Oligocene Anthropoid <em>Aegyptopithecus zeuxis<\/em> (Catarrhini, Propliopithecidae).\u201d <em>Proceedings of the National Academy of Sciences of the United States of America<\/em> 104 (21): 8731\u20138736.<\/p>\r\n<p class=\"import-Normal\">Simpson, George Gaylord. 1933. \u201cThe \u2018Plagiaulacoid\u2019 Type of Mammalian Dentition: A Study of Convergence.\u201d <em>Journal of Mammalogy<\/em> 14 (2): 97\u2013107.<\/p>\r\n<p class=\"import-Normal\">Simpson, George Gaylord. 1940. \u201cReview of the Mammal-Bearing Tertiary of South America.\u201d <em>Proceedings of the American Philosophical Society<\/em> 83 (5): 649\u2013709.<\/p>\r\n<p class=\"import-Normal\">Simpson, George Gaylord. 1967. \u201cThe Tertiary Lorisiform Primates of Africa.\u201d <em>Bulletin of the Museum of Comparative Zoology at Harvard University<\/em> 136: 39\u201362.<\/p>\r\n<p class=\"import-Normal\">Smith, G. Elliot. 1912. \u201cThe Evolution of Man.\u201d <em>Smithsonian Institute Annual Report <\/em>2012: 553\u2013572.<\/p>\r\n<p class=\"import-Normal\">Smith, Thierry, Kenneth D. Rose, and Philip D. Gingerich. 2006. \u201cRapid Asia\u2013Europe\u2013North America Geographic Dispersal of Earliest Eocene Primate <em>Teilhardina<\/em> during the Paleocene\u2013Eocene Thermal Maximum.\u201d <em>Proceedings of the National Academy of Sciences of the United States of America<\/em> 103 (30): 11223\u201311227.<\/p>\r\n<p class=\"import-Normal\">Stehlin, Hans G. 1912. \u201cDie s\u00e4ugetiere des schweizerischen Eocaens. Siebenter teil, erst h\u00e4lfte: <em>Adapis<\/em>\u201d [\u201cThe Mammals of the Swiss Eocene. Part Seven, First Half: Adapis\u201d]. <em>Abhandlungen der Schweizerischen Pal\u00e4ontologischen Gesellschaft<\/em> 38: 1165\u20131298.<\/p>\r\n<p class=\"import-Normal\">Strait, Suzanne G. 2001. \u201cDietary Reconstruction of Small-Bodied Omomyoid Primates.\u201d <em>Journal of Vertebrate Paleontology<\/em> 21 (2): 322\u2013334.<\/p>\r\n<p class=\"import-Normal\">Sussman, Robert W. 1991. \u201cPrimate Origins and the Evolution of Angiosperms.\u201d <em>American Journal of Primatology<\/em> 23 (4): 209\u2013223.<\/p>\r\n<p class=\"import-Normal\">Suwa, Gen, Reiko T. Kono, Shigehiro Katoh, Berhane Asfaw, and Yonas Beyene. 2007. \u201cA New Species of Great Ape from the Late Miocene Epoch in Ethiopia.\u201d <em>Nature<\/em> 448 (7156): 921\u2013924.<\/p>\r\n<p class=\"import-Normal\">Teaford, Mark F., Mary C. Maas, and Elwyn L. Simons. 1996. \u201cDental Microwear and Microstructure in Early Oligocene Primates from the Fayum, Egypt: Implications for Diet.\u201d <em>American Journal of Physical Anthropology<\/em> 101 (4): 527\u2013543.<\/p>\r\n<p class=\"import-Normal\">Ungar, Peter S., and Richard F. Kay. 1995. \u201cThe Dietary Adaptations of European Miocene Catarrhines.\u201d <em>Proceedings of the National Academy of Sciences of the United States of America<\/em> 92 (12): 5479\u20135481.<\/p>\r\n<p class=\"import-Normal\">Wang, Cui-Bin, Ling-Xia Zhao, Chang-Zhu Jin, Yuan Wang, Da-Gong Qin, and Wen-Shi Pan. 2014. \u201cNew Discovery of Early Pleistocene Orangutan Fossils from Sanhe Cave in Chongzuo, Guangxi, Southern China.\u201d <em>Quaternary International<\/em> 354: 68\u201374.<\/p>\r\n<p class=\"import-Normal\">Ward, C. V., A. Walker, and M. F. Teaford. 1991. \u201c<em>Proconsul<\/em> Did Not Have a Tail.\u201d <em>Journal of Human Evolution<\/em> 21 (3): 215\u2013220.<\/p>\r\n<p class=\"import-Normal\">Wheeler, Brandon C. 2010. \u201cCommunity Ecology of the Middle Miocene Primates of La Venta, Colombia: The Relationship between Ecological Diversity, Divergence Time, and Phylogenetic Richness.\u201d <em>Primates<\/em> 51 (2): 131\u2013138.<\/p>\r\n<p class=\"import-Normal\">Williams, Blythe A., and Richard F. Kay. 1995. \u201cThe Taxon Anthropoidea and the Crown Clade Concept.\u201d <em>Evolutionary Anthropology<\/em> 3 (6): 188\u2013190.<\/p>\r\n<p class=\"import-Normal\">Williams, Blythe A., Richard F. Kay, and E. Christopher Kirk. 2010a. \u201cNew Perspectives on Anthropoid Origins.\u201d <em>Proceedings of the National Academy<\/em> <em>of the United States of America<\/em> 107 (11): 4797\u20134804.<\/p>\r\n<p class=\"import-Normal\">Williams, Blythe A., Richard F. Kay, E. Christopher Kirk, and Callum F. Ross. 2010b. \u201c<em>Darwinius masillae<\/em> Is a European Middle Eocene Stem Strepsirrhine\u2014A Reply to Franzen et al.\u201d <em>Journal of Human Evolution<\/em> 59(5): 567\u2013573.<\/p>\r\n<p class=\"import-Normal\">Wilson Mantilla, G. P., S. G. B. Chester, W. A. Clemens, J. R. Moore, C. J. Sprain, B. T. Hovatter, W. S. Mitchell, W. W. Mans, R. Mundil, and P. R. Renne. 2021. \u201cEarliest Palaeocene Purgatoriids and the Initial Radiation of Stem Primates.\u201d <em>Royal Society Open Science<\/em> 8(2):210050. doi:10.1098\/rsos.210050.<\/p>\r\n\r\n<h2 class=\"import-Normal\">Acknowledgments<\/h2>\r\n<p class=\"import-Normal\">We are immensely grateful to the editors of this book, Drs. Beth Shook, Lara Braff, Katie Nelson, and Kelsie Aguilera, for their time and commitment to making this knowledge freely accessible to all, and for giving us the opportunity to participate in this important project.<\/p>\r\n\r\n<\/div>","rendered":"<div class=\"__UNKNOWN__\">\n<p class=\"import-Normal\">Jonathan M. G. Perry, Ph.D., Western University of Health Sciences<\/p>\n<p class=\"import-Normal\">Stephanie L. Canington, Ph.D., University of Pennsylvania<\/p>\n<p class=\"import-Normal\"><em>This chapter is a revision from &#8220;<\/em><a class=\"rId7\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Chapter 8: Primate Evolution<\/em><\/a><em>\u201d by Jonathan M. G. Perry and Stephanie L. Canington. In <\/em><a class=\"rId8\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\"><em>Explorations: An Open Invitation to Biological Anthropology, first edition<\/em><\/a><em>, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under <\/em><a class=\"rId9\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\"><em>CC BY-NC 4.0<\/em><\/a><em>. <\/em><\/p>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<h2 class=\"textbox__title\"><span style=\"color: #000000\">Learning Objectives<\/span><\/h2>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Understand the major trends in primate evolution from the origin of primates to the origin of our own species.<\/li>\n<li>Learn about primate adaptations and how they characterize major primate groups.<\/li>\n<li>Discuss the kinds of evidence that anthropologists use to find out how extinct primates are related to each other and to living primates.<\/li>\n<li>Recognize how the changing geography and climate of Earth have influenced where and when primates have thrived or gone extinct.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p class=\"import-Normal\">The first fifty million years of primate evolution was a series of <strong>adaptive radiations<\/strong> leading to the diversification of the earliest lemurs, monkeys, and apes. The primate story begins in the canopy and understory of conifer-dominated forests, with our small, furtive ancestors subsisting at night, beneath the notice of day-active dinosaurs.<\/p>\n<p class=\"import-Normal\">From the ancient <strong>plesiadapiforms<\/strong> (archaic primates) to the earliest groups of true primates (<strong>euprimates<\/strong>) (Bloch and Boyer 2002), the origin of our own order is characterized by the struggle for new food sources and microhabitats in the arboreal setting. Climate change forced major extinctions as the northern continents became increasingly dry, cold, and seasonal and as tropical rainforests gave way to deciduous forests, woodlands, and eventually grasslands. Lemurs, lorises, and tarsiers\u2014once diverse groups containing many species\u2014became rare, except for lemurs in Madagascar, where there were no anthropoid competitors and perhaps few predators. Meanwhile, <strong>anthropoids<\/strong> (monkeys and apes) likely emerged in Asia and then dispersed across parts of the northern hemisphere, Africa, and ultimately South America. The movement of continents, shifting sea levels, and changing patterns of rainfall and vegetation contributed to the developing landscape of primate biogeography, morphology, and behavior. Today\u2019s primates provide modest reminders of the past diversity and remarkable adaptations of their extinct relatives. This chapter explores the major trends in primate evolution from the origin of the Order Primates to the beginnings of our own lineage, providing a window into these stories from our ancient past.<\/p>\n<h2 class=\"import-Normal\">Major Hypotheses About Primate Origins<\/h2>\n<p class=\"import-Normal\">For many groups of mammals, there is a key feature that led to their success. A good example is powered flight in bats. Primates lack a feature like this (see Chapter 5). Instead, if there is something unique about primates, it is probably a group of features rather than one single thing. Because of this, anthropologists and paleontologists struggle to describe an ecological scenario that could explain the rise and success of our own order. Three major hypotheses have been advanced to consider the origin of primates and to explain what makes our order distinct among mammals (Figure 9.1); these are described below.<\/p>\n<figure id=\"attachment_277\" aria-describedby=\"caption-attachment-277\" style=\"width: 634px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-255\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2023\/03\/8.1.jpg\" alt=\"Primates swinging in tree, eating an insect, and eating fruit.\" width=\"634\" height=\"221\" \/><figcaption id=\"caption-attachment-277\" class=\"wp-caption-text\">Figure 9.1: The three major hypotheses are (a) the arboreal hypothesis, (b) the visual predation hypothesis, and (c) the angiosperm-primate coevolution hypothesis. Credit: Primate origin hypotheses original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by <a class=\"rId13\" href=\"https:\/\/marynelsonstudio.com\">Mary Nelson<\/a> is under a <a class=\"rId14\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Arboreal Hypothesis<\/strong><\/h3>\n<p class=\"import-Normal\">In the 1800s, many anthropologists viewed all animals in relation to humans. That is, animals that were more like humans were considered to be more \u201cadvanced\u201d and those lacking humanlike features were considered more \u201cprimitive.\u201d This way of thinking was particularly obvious in studies of primates. A more modern way of referring to members of a group that lack certain evolutionary innovations seen in other members is to call them <strong>plesiomorphic<\/strong> (literally \u201canciently shaped\u201d). The state of their morphological features is sometimes referred to as <strong>ancestral<\/strong><strong> traits<\/strong>.<\/p>\n<p class=\"import-Normal\">Thus, when anthropologists sought features that separate primates from other mammals, they focused on features that were least developed in lemurs and lorises, more developed in monkeys, and most developed in apes (Figure 9.2). Frederic Wood Jones, one of the leading anatomist-anthropologists of the early 1900s, is usually credited with the Arboreal Hypothesis of primate origins (Jones 1916). This hypothesis holds that many of the features of primates evolved to improve locomotion in the trees; this way of getting around is referred to as arboreal. For example, the grasping hands and feet of primates are well suited to gripping tree branches of various sizes and our flexible joints are good for reorienting the extremities in many different ways. A mentor of Jones, Grafton Elliot Smith, had suggested that the reduced olfactory system, acute vision, and forward-facing eyes of primates are adaptations for making accurate leaps and bounds through a complex, three-dimensional canopy (Smith 1912). The forward orientation of the eyes in primates causes the visual fields to overlap, enhancing depth perception, especially at close range. Evidence to support this hypothesis includes the facts that many extant primates are arboreal, and the plesiomorphic members of most primate groups are dedicated arborealists. The Arboreal Hypothesis was well accepted by most anthropologists at the time and for decades afterward.<\/p>\n<figure style=\"width: 663px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image27-2.png\" alt=\"Diagram shows primates descended from Plesiadapiforms.\" width=\"663\" height=\"543\" \/><figcaption class=\"wp-caption-text\">Figure 9.2: Primate family tree showing major groups. Disconnected lines show uncertainty about relationships. Two lines lead to tarsiers from different possible groups of origin. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit: <a class=\"rId16\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Primate family tree (Figure 8.2)<\/a> by Jonathan M. G. Perry is under a <a class=\"rId17\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Visual Predation Hypothesis<\/strong><\/h3>\n<p class=\"import-Normal\">In the late 1960s and early 1970s, Matt Cartmill studied and tested the idea that the characteristic features of primates evolved in the context of arboreal locomotion. Cartmill noted that squirrels climb trees (and even vertical walls) very effectively, even though they lack some of the key adaptations of primates. As members of the Order Rodentia, squirrels also lack the hand and foot anatomy of primates. They have claws instead of flattened nails and their eyes face more laterally than those of primates. Cartmill reasoned that there must be some other explanation for the unique traits of primates. He noted that some nonarboreal animals share at least some of these traits with primates; for example, cats and predatory birds have forward-facing eyes that enable visual field overlap. Cartmill suggested that the unique suite of features in primates is an adaptation to detecting insect prey and guiding the hands (or feet) to catch insects (Cartmill 1972). His hypothesis emphasizes the primary role of vision in prey detection and capture; it is explicitly comparative, relying on form-function relationships in other mammals and nonmammalian vertebrates. According to Cartmill, many of the key features of primates evolved for preying on insects in this special manner (Cartmill 1974).<\/p>\n<h3 class=\"import-Normal\"><strong>Angiosperm-Primate Coevolution Hypothesis<\/strong><\/h3>\n<p class=\"import-Normal\">The visual predation hypothesis was unpopular with some anthropologists. One reason for this is that many primates today are not especially predatory. Another is that, whereas primates do seem well adapted to moving around in the smallest, terminal branches of trees, insects are not necessarily easier to find there. A counterargument to the visual predation hypothesis is the angiosperm-primate coevolution hypothesis. Primate ecologist Robert Sussman (Sussman 1991) argued that the few primates that eat mostly insects often catch their prey on the ground rather than in tree branches. Furthermore, predatory primates often use their ears more than their eyes to detect prey. Finally, most early primate fossils show signs of having been omnivorous rather than insectivorous. Instead, he argued, the earliest primates were probably seeking fruit. Fruit (and flowers) of angiosperms (flowering plants) often develop in the terminal branches. Therefore, any mammal trying to access those fruits must possess anatomical traits that allow them to maintain their hold on thin branches and avoid falling while reaching for the fruits. Primates likely evolved their distinctive visual traits and extremities in the Paleocene (approximately 65 million to 54 million years ago) and Eocene (approximately 54 million to 34 million years ago) epochs, just when angiosperms were going through a revolution of their own\u2014the evolution of large, fleshy fruit that would have been attractive to a small arboreal mammal. Sussman argued that, just as primates were evolving anatomical traits that made them more efficient fruit foragers, angiosperms were also evolving fruit that would be more attractive to primates to promote better seed dispersal. This mutually beneficial relationship between the angiosperms and the primates was termed coevolution or more specifically <strong>diffuse coevolution<\/strong>.<\/p>\n<p class=\"import-Normal\">At about the same time, D. Tab Rasmussen noted several parallel traits in primates and the South American woolly opossum, <em>Caluromys<\/em>. He argued that early primates were probably foraging on both fruits and insects (Rasmussen 1990). As is true of <em>Caluromys<\/em> today, early primates probably foraged for fruits in the terminal branches of angiosperms, and they probably used their visual sense to aid in catching insects. Insects are also attracted to fruit (and flowers), so these insects represent a convenient opportunity for a primarily fruit-eating primate to gather protein. This solution is a compromise between the visual predation hypothesis and the angiosperm-primate coevolution hypothesis. It is worth noting that other models of primate origins have been proposed, and these include the possibility that no single ecological scenario can account for the origin of primates.<\/p>\n<h2 class=\"import-Normal\">The Origins of Primates<\/h2>\n<h3 class=\"import-Normal\"><strong>Paleocene: Mammals in the Wake of Dinosaur Extinctions<\/strong><\/h3>\n<p class=\"import-Normal\">Placental mammals, including primates, originated in the Mesozoic Era (approximately 251 million to 65.5 million years ago), the Age of Dinosaurs. During this time, most placental mammals were small, probably nocturnal, and probably avoided predators via camouflage and slow, quiet movement. It has been suggested that the success and diversity of the dinosaurs constituted a kind of ecological barrier to Mesozoic mammals. The extinction of the dinosaurs (and many other organisms) at the end of the Cretaceous Period (approximately 145.5\u201365.5 million years ago) might have opened up these ecological niches, leading to the increased diversity and disparity in mammals of the Tertiary Period (approximately 65.5\u20132.5 million years ago).<\/p>\n<p class=\"import-Normal\">The Paleocene was the first epoch in the Age of Mammals. Soon after the Cretaceous-Tertiary (K-T) extinction event, new groups of placental mammals appear in the fossil record. Many of these groups achieved a broad range of sizes and lifestyles as well as a great number of species before declining sometime in the Eocene (or soon thereafter). These groups were ultimately replaced by the modern orders of placental mammals (Figure 9.3). It is unknown whether these replacements occurred gradually, for example by competitive exclusion, or rapidly, perhaps by sudden geographic dispersals with replacement. In some senses, the Paleocene might have been a time of recovery from the extinction event; it was cooler and more seasonal globally than the subsequent Eocene.<\/p>\n<figure style=\"width: 628px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image26.jpg\" alt=\"Person in front of a mural depicting forest animals.\" width=\"628\" height=\"511\" \/><figcaption class=\"wp-caption-text\">Figure 9.3: A mural of Eocene flora and fauna in North America. Credit: <a class=\"rId19\" href=\"https:\/\/flickr.com\/photos\/126377022@N07\/18404106406\">Image from page 27 of &#8220;Annual report for the year ended June 30 &#8230;&#8221; (1951)<\/a> by <a class=\"rId20\" href=\"https:\/\/flickr.com\/photos\/internetarchivebookimages\/\">Internet Archive Book Images<\/a> has been designated to the <a class=\"rId21\" href=\"https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/\">public domain (CC0)<\/a>. This photograph of the mural &#8220;Fauna and flora of middle Eocene in the Wyoming area&#8221; by Jay Matternes, was originally published by the <a class=\"rId22\" href=\"https:\/\/www.si.edu\/\">Smithsonian<\/a>, and can be viewed in context in the <a class=\"rId23\" href=\"https:\/\/archive.org\/details\/annualreportfory1961united\/page\/7\/mode\/1up?view=theater\">online version of this book<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Plesiadapiforms, the Archaic Primates<\/strong><\/h3>\n<p class=\"import-Normal\">The Paleocene epoch saw the emergence of several families of mammals that have been implicated in the origin of primates. These are the plesiadapiforms, which are archaic primates, meaning they possessed some primate features and lacked others. The word <em>plesiadapiform <\/em>means \u201calmost adapiform,\u201d a reference to some similarities between some plesiadapiforms and some adapiforms (or adapoids; later-appearing true primates)\u2014mainly in the molar teeth. Because enamel fossilizes better than other parts of the body, the molar teeth are the parts most often found and first discovered for any new species. Thus, dental similarities were often the first to be noticed by early mammalian paleontologists, partly explaining why plesiadapiforms were thought to be primates. Major morphological differences between plesidapiforms and euprimates (true primates) were observed later when more parts of plesiadapiform skeletons were discovered. Many plesiadapiforms have unusual anterior teeth and most have digits possessing claws rather than nails. So far, no plesiadapiform ever discovered has a postorbital bar (seen in extant <strong>strepsirrhines<\/strong>) or septum (as seen in <strong>haplorhines<\/strong>), and whether or not the <strong>auditory bulla<\/strong> was formed by the <strong>petrosal bone<\/strong> remains unclear for many plesiadapiform specimens. Nevertheless, there are compelling reasons (partly from new skeletal material) for including plesiadapiforms within the Order Primates.<\/p>\n<h4 class=\"import-Normal\"><em>Geographic and Temporal Distribution<\/em><\/h4>\n<p class=\"import-Normal\"><em>Purgatorius<\/em> is generally considered to be the earliest primate. This Paleocene mammal is known from teeth that are very plesiomorphic for a primate. It has some characteristics that suggest it is a basal plesiadapiform, but there is very little to link it specifically with euprimates (see Clemens 2004). Its ankle bones suggest a high degree of mobility, signaling an arboreal lifestyle (Chester et al. 2015). <em>Purgatorius<\/em> is plesiomorphic enough to have given rise to all primates, including the plesiadapiforms. However, new finds suggest that this genus was more diverse and had more differing tooth morphologies than previously appreciated (Wilson Mantilla et al. 2021). Plesiadapiform families were numerous and diverse during parts of the Paleocene in western North America and western Europe, with some genera (e.g., <em>Plesiadapis<\/em>; see Figure 9.4) living on both continents (Figure 9.5). Thus, there were probably corridors for plesiadapiform dispersal between the two continents, and it stands to reason that these mammals were living all across North America, including in the eastern half of the continent and at high latitudes. A few plesiadapiforms have been described from Asia (e.g., <em>Carpocristes<\/em>), but the affinities of these remain uncertain.<\/p>\n<div style=\"text-align: left\">\n<table class=\"aligncenter\" style=\"width: 473.25pt\">\n<caption>Figure 9.4: Families of plesiadapiforms with example genera and traits: a table. Credit: Plesiadapiforms table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId24\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\n<thead>\n<tr style=\"height: 25pt\">\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\n<p>&nbsp;<\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr class=\"Table1-R\" style=\"height: 17pt\">\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Paromomyidae<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Ignacius<\/em><\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Long, dagger-like, lower incisor.<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">North America and Europe<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early Paleocene to Late Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table1-R\" style=\"height: 18pt\">\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Carpolestidae<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Carpolestes<\/em><\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Plagiaulacoid dentition. Limb adaptations to terminal branch feeding. Grasping big toe.<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">North America, Europe, and Asia<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle Paleocene to Early Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table1-R\" style=\"height: 16pt\">\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Plesiadapidae<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Plesiadapis<\/em><\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Mitten-like upper incisor. Diastema. Large body size for group.<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">North America and Europe<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle Paleocene to Early Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table1-R\" style=\"height: 1pt\">\n<td class=\"Table1-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\n<\/td>\n<td class=\"Table1-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\n<p class=\"import-Normal\">\n<\/td>\n<\/tr>\n<tr>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<figure id=\"attachment_277\" aria-describedby=\"caption-attachment-277\" style=\"width: 555px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-258\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image5-5-e1691791897574.png\" alt=\"Global map with not fully formed continents.\" width=\"555\" height=\"308\" \/><figcaption id=\"caption-attachment-277\" class=\"wp-caption-text\">Figure 9.5: Map of the world in the Paleocene, highlighting plesiadapiform localities on lands that would become North America, southern Europe, and eastern Asia. Credit: <a class=\"rId26\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Paleocene Map with Plesiadapiform Localities (Figure 8.4)<\/a> original to<a class=\"rId27\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\"> Expl<\/a><a class=\"rId28\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">orations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId29\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId30\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 211.<\/figcaption><\/figure>\n<h4 class=\"import-Normal\"><em>General Morphological Features<\/em><\/h4>\n<p class=\"import-Normal\">Although there is much morphological variation among the families of plesiadapiforms, some common features unite the group. Most plesiadapiforms were small, the largest being about three kilograms (approximately 7 lbs.; <em>Plesiadapis cookei<\/em>). They had small brains and fairly large snouts, with eyes that faced more laterally than in euprimates. Many species show reduction and\/or loss of the canine and anterior premolars, with the resulting formation of a rodent-like <strong>diastema <\/strong>(a pronounced gap between the premolars and the incisors, with loss of at least the canine); this probably implies a herbivorous diet. Some families appear to have had very specialized diets, as suggested by unusual tooth and jaw shapes.<\/p>\n<p class=\"import-Normal\">Arguably the most interesting and unusual family of plesiadapiforms is the Carpolestidae. They are almost exclusively from North America (with a couple of possible members from Asia), and mainly from the Middle and Late Paleocene. Their molars are not very remarkable, being quite similar to those of some other plesiadapiforms (e.g., Plesiadapidae). However, their lower posterior premolars (p4) are laterally compressed and blade-like with vertical serrations topped by tiny cuspules. This unusual dental morphology is termed <strong><em>plagiaulacoid<\/em><\/strong>  (Simpson 1933). The upper premolar occlusal surfaces are broad and are covered with many small cuspules; the blade-like lower premolar might have cut across these cuspules, between them, or both.<\/p>\n<figure style=\"width: 357px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image13-5.png\" alt=\"Front view of skull with pointed teeth.\" width=\"357\" height=\"322\" \/><figcaption class=\"wp-caption-text\">Figure 9.25: Skull of Victoriapithecus macinnesi. Credit: Victoriapithecus macinnesi skull photo taken at the Musee d&#8217;Histoire Naturelle, Paris by Ghedoghedo is under a CC BY-SA 3.0 License.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Many plesiadapiforms have robust limb bones with hallmarks of arboreality. Instead of having nails, most taxa had sharp claws on most or all of the digits. The extremities show grasping abilities comparable to those of primates and some arboreal marsupials. Nearly complete skeletons have yielded a tremendous wealth of information on locomotor and foraging habits. Many plesiadapiforms appear to have been able to cling to vertical substrates (like a broad tree trunk) using their sharp claws, propelling themselves upward using powerful hindlimbs, bounding along horizontal supports, grasping smaller branches, and moving head-first down tree trunks. In carpolestids in particular, the skeleton appears to have been especially well adapted to moving slowly and carefully in small terminal branches (Figure 9.6).<\/p>\n<\/div>\n<div class=\"textbox shaded\">\n<h3 class=\"import-Normal\">Dig Deeper: Debate: Relationship of Plesiadapiforms to True Primates<\/h3>\n<p class=\"import-Normal\">In the middle of the twentieth century, treeshrews (Order Scandentia) were often considered part of the Order Primates, based on anatomical similarities between some treeshrews and primates. For many people, plesiadapiforms represented intermediates between primates and treeshrews, so plesiadapiforms were included in Primates as well.<\/p>\n<p class=\"import-Normal\">Studies of reproduction and brain anatomy in treeshrews and lemurs suggested that treeshrews are not primates (e.g., Martin 1968). This was soon followed by the suggestion to also expel plesiadapiforms (Martin 1972) from the Order Primates. Like treeshrews, plesiadapiforms lack a postorbital bar, nails, and details of the ear region that characterize true primates. Many paleoanthropologists were reluctant to accept this move to banish plesiadapiforms (e.g., F. S. Szalay, P. D. Gingerich).<\/p>\n<p class=\"import-Normal\">Later, K. Christopher Beard (1990) found that in some ways, the digits of paromomyid plesiadapiforms are actually more similar to those of dermopterans (Order Dermoptera), the closest living relatives of primates, than they are to those of primates themselves (but see Krause 1991). At the same time, Richard Kay and colleagues (1990) found that cranial circulation patterns and auditory bulla morphology in the paromomyid, <em>Ignacius <\/em>(see Figure 9.4), are more like those of dermopterans than of primates.<\/p>\n<p class=\"import-Normal\">For many anthropologists, this one-two punch effectively removed plesiadapiforms from the Order Primates. In the last two decades, the tide of opinion has turned again, with many researchers reinstating plesiadapiforms as members of the Order Primates. New and more complete specimens demonstrate that the postcranial skeletons of plesiadapiforms, including the hands and feet, were primate-like, not dermorpteran-like (Bloch and Boyer 2002, 2007). New fine-grained CT scans of relatively complete plesiadapiform skulls revealed that they share some key traits with primates to the exclusion of other placental mammals (Bloch and Silcox 2006). Most significant was the suggestion that <em>Carpolestes simpsoni <\/em>possessed an auditory bulla formed by the <strong>petrosal <\/strong><strong>bone<\/strong>, like in all living primates.<\/p>\n<p class=\"import-Normal\">The debate about the status of plesiadapiforms continues, owing to a persistent lack of key bones in some species and owing to genuine complexity of the anatomical traits involved. Maybe plesiadapiforms were the ancestral stock from which all primates arose, with some plesiadapiforms (e.g., carpolestids) nearer to the primate <strong>stem<\/strong> than others.<\/p>\n<\/div>\n<div class=\"__UNKNOWN__\">\n<h3 class=\"import-Normal\"><strong>Adapoids and Omomyoids, the First True Primates<\/strong><\/h3>\n<h4 class=\"import-Normal\"><em>Geographic and Temporal Distribution<\/em><\/h4>\n<p class=\"import-Normal\">The first universally accepted fossil primates are the adapoids (Superfamily <strong>Adapoidea<\/strong>) and the omomyoids (Superfamily <strong>Omomyoidea)<\/strong>. These groups become quite distinct over evolutionary time, filling mutually exclusive niches for the most part. However, the earliest adapoids are very similar to the earliest omomyoids.<\/p>\n<p class=\"import-Normal\">The adapoids were mainly diurnal and herbivorous, with some achieving larger sizes than any plesiadapiforms (10 kg; 22 lbs.). By contrast, the omomyoids were mainly nocturnal, insectivorous and frugivorous, and small.<\/p>\n<p class=\"import-Normal\">Both groups appear suddenly at the start of the Eocene, where they are present in western North America, western Europe, and India (Figure 9.7). This wide dispersal of early primates was probably due to the presence of rainforest corridors extending far into northern latitudes.<\/p>\n<figure id=\"attachment_277\" aria-describedby=\"caption-attachment-277\" style=\"width: 539px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-260\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image22-3-e1691792023503.png\" alt=\"Global map with not fully formed continents and omomyoid localities.\" width=\"539\" height=\"317\" \/><figcaption id=\"caption-attachment-277\" class=\"wp-caption-text\">Figure 9.7: Map of the world in the Eocene, highlighting adapoid and omomyoid localities on lands that would become North America, southern Europe, Africa, and Asia. Credit: <a class=\"rId36\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Eocene Map with Adapoid and Omomyoid Localities (Figure 8.6)<\/a> original to <a class=\"rId37\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId38\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId39\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 229.<\/figcaption><\/figure>\n<p class=\"import-Normal\">In North America and Europe, both groups achieved considerable diversity in the Middle Eocene, then mostly died out at the end of that epoch (Figure 9.8). In some Eocene rock formations in the western United States, adapoids and omomyoids make up a major part of the mammalian fauna. The Eocene of India has yielded a modest diversity of euprimates, some of which are so plesiomorphic that it is difficult to know whether they are adapoids or omomyoids (or even early anthropoids).<\/p>\n<div style=\"text-align: left\">\n<table class=\"aligncenter\" style=\"width: 473.25pt\">\n<caption>Figure 9.8: Families of adapoids and omomyoids with example genera and traits: a table. Credit: Adapoids and omomyoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId40\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\n<thead>\n<tr style=\"height: 25pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\n<p>&nbsp;<\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr class=\"Table2-R\" style=\"height: 18pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Cercamoniidae<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Donrussellia<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Variable in tooth number and jaw shape.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Europe and Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early to Late Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Asiadapidae<sup>2<\/sup><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Asiadapis<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Plesiomorphic teeth and jaw resemble early Omomyids.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Caenopithecidae<sup>3<\/sup><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Darwinius<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Robust jaws with crested molars. Fewer premolars.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Europe, Africa, North America, and Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle to Late Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Adapidae<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Adapis<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Fused mandible. Long molar crests. Large size and large chewing muscles.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Europe<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Late Eocene to Early Oligocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Sivaladapidae<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Sivaladapis<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Some large with robust jaws.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle Eocene to Late Miocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Notharctidae<sup>4<\/sup><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Notharctus<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Canine sexual dimorphism. Lemur-like skull. Clinging and leaping adaptations.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">North America and Europe<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early to Middle Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Omomyidae<sup>5<\/sup><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Teilhardina<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Small, nocturnal, frugivorous or insectivorous. Tarsier-like skull in some.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">North America, Europe, and Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early Eocene to Early Miocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 16pt\">\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Microchoeridae<sup>6<\/sup><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Necrolemur<\/em><\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Long bony ear tubes. Tarsier-like lower limb adaptations for leaping.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Europe and Asia<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Early Eocene to Early Oligocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table2-R\" style=\"height: 1pt\">\n<td class=\"Table2-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\n<p class=\"import-Normal\"><sup>2<\/sup> See Dunn et al. 2016 and Rose et al. 2018.<\/p>\n<p class=\"import-Normal\"><sup>3<\/sup> See Kirk and Williams 2011 and Seiffert et al. 2009.<\/p>\n<p class=\"import-Normal\"><sup>4<\/sup> See Gregory 1920.<\/p>\n<p class=\"import-Normal\"><sup>5<\/sup> See Beard and MacPhee 1994 and Strait 2001.<\/p>\n<p class=\"import-Normal\"><sup>6<\/sup> See Schmid 1979.<\/p>\n<\/td>\n<td class=\"Table2-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\n<p class=\"import-Normal\">\n<\/td>\n<\/tr>\n<tr>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p class=\"import-Normal\">Adapoids and omomyoids barely survived the Eocene-Oligocene extinctions, when colder temperatures, increased seasonality, and the retreat of rainforests to lower latitudes led to changes in mammalian biogeography. In North America, one genus (originally considered an omomyoid but recently reclassified as Adapoidea) persisted until the Miocene: <em>Ekgmowechashala<\/em> (Rose and Rensberger 1983). This taxon has highly unusual teeth and might have been a late immigrant to North America from Asia. In Asia, one family of adapoids, the Sivaladapidae, retained considerable diversity as late as the Late Miocene.<\/p>\n<h4 class=\"import-Normal\"><em>Adapoid Diversity<\/em><\/h4>\n<p class=\"import-Normal\">Adapoids were very diverse, particularly in the Eocene of North America and Europe. They can be divided into six families, with a few species of uncertain familial relationship. As a group, adapoids have some features in common, although much of what they share is plesiomorphic. Important features include the hallmarks of euprimates: postorbital bar, flattened nails, grasping extremities, and a petrosal bulla (Figures 9.9 and 9.10). In addition, some adapoids retain the ancestral dental formula of 2.1.4.3; that is, in each quadrant of the mouth, there are two incisors, one canine, four premolars, and three molars. In general, the incisors are small compared to the molars, but the canines are relatively large, with sexual dimorphism in some species. Cutting crests on the molars are well developed in some species, and the two halves of the mandible were fused at the midline in some species. Some adapoids were quite small (<em>Anchomomys <\/em>at a little over 100 g), and some were quite large (<em>Magnadapis<\/em> at 10 kg; 22 lbs.). Furthermore, the spaces and attachment features for the chewing muscles were truly enormous in some species, suggesting that these muscles were very large and powerful. Taken together, this suggests an overall adaptive profile of diurnal herbivory. The canine sexual dimorphism in some species suggests a possible mating pattern of polygyny, as males in polygynous primate species often compete with each other for mates and have especially large canine teeth.<\/p>\n<figure style=\"width: 548px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image18-1.jpg\" alt=\"Three partial animal crania.\" width=\"548\" height=\"350\" \/><figcaption class=\"wp-caption-text\">Figure 9.9: Representative crania of Adapidae from Museum d\u2019Histoire Naturelle Victor Brun, a natural history museum in Montauban, France. The white scale bar is 1 cm long. Credit: <a class=\"rId43\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Representative crania of adapids (European adapoids, (Figure 8.7)<\/a> from the <a class=\"rId44\" href=\"https:\/\/www.museum.montauban.com\/\">Museum d\u2019Histoire Naturelle Victor Brun in Montauban, France<\/a> original to <a class=\"rId45\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology <\/a>by Jonathan M. G. Perry is under a <a class=\"rId46\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<figure style=\"width: 547px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image19-2.jpg\" alt=\"Side views of small rodentlike skeleton with long tail.\" width=\"547\" height=\"525\" \/><figcaption class=\"wp-caption-text\">Figure 9.10: Darwinius masillae, a member of the Caenopithecidae. The slab on the left is Plate A and the slab on the right is Plate B. The parts of the skeleton in B that are outside of the dashed lines were fabricated. Credit: <a class=\"rId48\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Darwinius%20masillae%20holotype%20slabs.jpg\">Darwinius masillae holotype slabs<\/a> by Jens L. Franzen, Philip D. Gingerich, J\u00f6rg Habersetzer1, J\u00f8rn H. Hurum, Wighart von Koenigswald, B. Holly Smith is under a <a class=\"rId49\" href=\"https:\/\/creativecommons.org\/licenses\/by\/2.5\/legalcode\">CC BY 2.5 License<\/a>. Originally from Franzen et al. 2009.<\/figcaption><\/figure>\n<h4 class=\"import-Normal\"><em>Omomyoid Diversity<\/em><\/h4>\n<p class=\"import-Normal\">Like adapoids, omomyoids appeared suddenly at the start of the Eocene and then became very diverse with most species dying out before the Oligocene. Omomyoids are known from thousands of jaws with teeth, relatively complete skulls for about a half-dozen species, and very little postcranial material. Omomyoids were relatively small primates, with the largest being less than three kilograms (approximately 7 lbs.; <em>Macrotarsius montanus<\/em>). All known crania possess a postorbital bar, which in some has been described as \u201cincipient closure.\u201d Some\u2014but not all\u2014known crania have an elongated bony ear tube extending lateral to the location of the eardrum, a feature seen in living tarsiers and <strong>catarrhines<\/strong>. The anterior teeth tend to be large, with canines that are usually not much larger than the incisors. Often it is difficult to distinguish closely related species using molar morphology, but the premolars tend to be distinct from one species to another. The postcranial skeleton of most omomyoids shows hallmarks of leaping behavior reminiscent of that of tarsiers. In North America, omomyoids became very diverse and abundant. In fact, omomyoids from Wyoming are sufficiently abundant and from such stratigraphically controlled conditions that they have served as strong evidence for the gradual evolution of anatomical traits over time (Rose and Bown 1984).<\/p>\n<p class=\"import-Normal\"><em>Teilhardina <\/em>(Figure 9.11; see Figure 9.2) is one of the earliest and arguably the most plesiomorphic of omomyoids. <em>Teilhardina<\/em> has several species, most of which are from North America, with one from Europe (<em>T. belgica<\/em>) and one from Asia (<em>T. asiatica<\/em>). The species of this genus are anatomically similar and the deposits from which they are derived are roughly contemporaneous. Thus, this small primate likely dispersed across the northern continents very rapidly (Smith et al. 2006).<\/p>\n<figure style=\"width: 545px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image3-1.jpg\" alt=\"World map with primates jumping across forested areas.\" width=\"545\" height=\"289\" \/><figcaption class=\"wp-caption-text\">Figure 9.11: A map of the world during the early Eocene showing one hypothesis for the direction of dispersal of the omomyoid Teilhardina. The map depicts primates hopping from continent to continent (East to West) via the forest corridors at high latitudes. Credit: <a href=\"https:\/\/www.pnas.org\/content\/103\/30\/11223\">Paleogeographic map showing hypothetical migration routes of Teilhardina (Figure 1)<\/a> by Thierry Smith, Kenneth D. Rose, and Philip D. Gingerich. 2006. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America <\/a>103 (30): 11223\u201311227. Copyright (2006) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a><\/figcaption><\/figure>\n<h2 class=\"import-Normal\">The Emergence of Modern Primate Groups<\/h2>\n<h3 class=\"import-Normal\"><strong>Origins of Crown Strepsirrhines<\/strong><\/h3>\n<p class=\"import-Normal\">Until the turn of this century, very little was known about the origins of the <strong>crown<\/strong> (living) strepsirrhines. The Quaternary record of Madagascar contains many amazing forms of lemurs, including giant sloth-like lemurs, lemurs with perhaps monkey-like habits, lemurs with koala-like habits, and even a giant aye-aye (Godfrey and Jungers 2002). However, in Madagascar, early Tertiary continental sediments are lacking, and there is no record of lemur fossils before the Pleistocene.<\/p>\n<p class=\"import-Normal\">The fossil record of galagos is slightly more informative. Namely, there are Miocene African fossils that are very likely progenitors of lorisids (Simpson 1967). However, these are much like modern galagos and do not reveal anything about the relationship between crown strepsirrhines and Eocene fossil primates (but see below regarding <em>Propotto<\/em>). A similar situation exists for lorises in Asia: there are Miocene representatives, but these are substantially like modern lorises. The discovery of the first definite <strong>toothcomb<\/strong> canine (a hallmark of stresirrhines) in 2003 provided the \u201csmoking gun\u201d for the origin of crown strepsirrhines (Seiffert et al. 2003). Recently, several other African primates have been recognized as having strepsirrhine affinities (Marivaux et al. 2013; Seiffert 2012). The enigmatic Fayum primate <em>Plesiopithecus<\/em> is known from a skull that has been compared to aye-ayes and to lorises (Godinot 2006; Simons and Rasmussen 1994a).<\/p>\n<p class=\"import-Normal\">The now-recognized diversity of stem strepsirrhines from the Eocene and Oligocene of Afro-Arabia is strong evidence to suggest that strepsirrhines originated in that geographic area. This implies that lorises dispersed to Asia subsequent to an African origin. It is unknown what the first strepsirrhines in Madagascar were like. However, it seems likely that the lemuriform-lorisiform split occurred in continental Africa, followed by dispersal of lemuriform stock to Madagascar. Recent evidence suggests that <em>Propotto<\/em>, a Miocene primate from Kenya originally described as a potto antecedent, actually forms a clade with <em>Plesiopithecus <\/em>and the aye-aye; this might suggest that strepsirrhines dispersed to Madagascar from continental Africa more than once (Gunnell et al. 2018).<\/p>\n<h3 class=\"import-Normal\"><strong>The Fossil Record of Tarsiers<\/strong><\/h3>\n<p class=\"import-Normal\">Tarsiers are so unusual that they fuel major debates about primate taxonomy. Tarsiers today are moderately diverse but geographically limited and not very different in their ecological habits\u2014especially considering that the split between them and their nearest living relative probably occurred over 50 million years ago. If omomyoids are excluded, then the fossil record of tarsiers is very limited. Two fossil species from the Miocene of Thailand have been placed in the genus <em>Tarsius<\/em>, as has an Eocene fossil from China (Beard et al. 1994). These, and <em>Xanthorhysis<\/em> from the Eocene of China, are all very tarsier-like. In fact, it is striking that <em>Tarsius eocaenus<\/em> from China was already so tarsier-like as early as the Eocene. This suggests that tarsiers achieved their current morphology very early in their evolution and have remained more or less the same while other primates changed dramatically. Two additional genera, <em>Afrotarsius<\/em> from the Oligocene of Egypt and Libya and <em>Afrasia<\/em> from the Eocene of Myanmar, have also been implicated in tarsier origins, though the relationship between them and tarsiers is unclear (Chaimanee et al. 2012). More recently, a partial skeleton of a small Eocene primate from China, <em>Archicebus achilles<\/em> (dated to approximately 55.8 million to 54.8 million years ago), was described as the most basal tarsiiform (Ni et al. 2013). This primate is reconstructed as a diurnal insectivore and an arboreal quadruped that did some leaping\u2014but not to the specialized degree seen in living tarsiers. The anatomy of the eye in living tarsiers suggests that their lineage passed through a diurnal stage, so <em>Archicebus<\/em> (and diurnal omomyoids) might represent such a stage.<\/p>\n<h3 class=\"import-Normal\"><strong>Climate Change and the Paleogeography of Modern Primate Origins<\/strong><\/h3>\n<p class=\"import-Normal\">Changing global climate has had profound effects on primate dispersal patterns and ecological habits over evolutionary time. Primates today are strongly tied to patches of trees and particular plant parts such as fruits, seeds, and immature leaves. It is no surprise, then, that the distribution of primates mirrors the distribution of forests. Today, primates are most diverse in the tropics, especially in tropical rainforests. Global temperature trends across the Tertiary have affected primate ranges. Following the Cretaceous-Tertiary extinction event, cooler temperatures and greater seasonality characterized the Paleocene. In the Eocene, temperatures (and probably rainfall) increased globally and rainforests likely extended to very high latitudes. During this time, euprimates became diverse. With cooling and increased aridity at the end of the Eocene, many primate extinctions occurred in the northern continents and the surviving primates were confined to lower latitudes in South America, Afro-Arabia, Asia, and southern Europe. Among these survivors are the progenitors of the living groups of primates: lemurs and lorises, tarsiers, <strong>platyrrhines<\/strong> (monkeys of the Americas), and catarrhines (monkeys and apes of Africa and Asia) (Figure 9.12).<\/p>\n<figure id=\"attachment_277\" aria-describedby=\"caption-attachment-277\" style=\"width: 539px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-264\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image2-5-e1691791570984.png\" alt=\"Map of world with gray continents.\" width=\"539\" height=\"306\" \/><figcaption id=\"caption-attachment-277\" class=\"wp-caption-text\">Figure 9.12: Map of key localities of early anthropoids on land that becomes Africa and southern Asia. Credit: <a class=\"rId56\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Oligocene Map with Key Early Anthropoid Localities (Figure 8.10)<\/a> original to <a class=\"rId57\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId58\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId59\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 265.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Competing Hypotheses for the Origin of Anthropoids<\/strong><\/h3>\n<p class=\"import-Normal\">There is considerable debate among paleoanthropologists as to the geographic origins of anthropoids. In addition, there is debate regarding the source group for anthropoids. Three different hypotheses have been articulated in the literature. These are the adapoid origin hypothesis, the omomyoid origin hypothesis, and the tarsier origin hypothesis (Figure 9.13).<\/p>\n<figure style=\"width: 419px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image24-1-1.jpg\" alt=\"Diagrams show three relationships among primate groups.\" width=\"419\" height=\"742\" \/><figcaption class=\"wp-caption-text\">Figure 9.13: Competing models of anthropoid origins. Branch lengths are not to scale. The omomyoid origin model and tarsier origin model do not make specific reference to the evolutionary position of strepsirrhines; however, they were included here for completeness. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\">A full text description of this image is available<\/a>. Credit: <a class=\"rId61\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Competing Trees for Anthropoid Origins (Figure 8.11)<\/a> original to <a class=\"rId62\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Jonathan M. G. Perry is under a <a class=\"rId63\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h4 class=\"import-Normal\"><em>Adapoid Origin Hypothesis<\/em><\/h4>\n<p class=\"import-Normal\">Resemblances between some adapoids and some extant anthropoids include fusion of the <strong>mandibular symphysis<\/strong>, overall robusticity of the chewing system, overall large body size, features that signal a diurnal lifestyle (like relatively small eye sockets), and ankle bone morphology. Another feature in common is canine sexual dimorphism, which is present in some species of adapoids (probably) and in several species of anthropoids.<\/p>\n<p class=\"import-Normal\">These features led some paleoanthropologists in the last half of the 20th century to suggest that anthropoids came from adapoid stock (Gingerich 1980; Simons and Rasmussen 1994b). One of the earliest supporters of the link between adapoids and anthropoids was Hans Georg Stehlin, who described much of the best material of adapoids and compared these Eocene primates to South American monkeys (Stehlin 1912). In more recent times, the adapoid origin hypothesis was reinforced by resemblances between these European adapoids (especially <em>Adapis <\/em>and <em>Leptadapis<\/em>) and some early anthropoids from the Fayum Basin (e.g., <em>Aegyptopithecus<\/em>, see below; Figure 9.14).<\/p>\n<div style=\"text-align: left\">\n<table class=\"aligncenter\" style=\"width: 473.25pt\">\n<caption>Figure 9.14: Families of early anthropoids with example genera and traits: a table. Credit: Early anthropoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId64\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\n<thead>\n<tr style=\"height: 25pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\n<p>&nbsp;<\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr class=\"Table3-R\" style=\"height: 18pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Propliopithecidae<sup>2<\/sup><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Aegyptopithecus<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Large size. Cranial sexual dimorphism, large canines. Robust jaws and rounded molars. Partially ossified ear tube (in some). Robust skeleton; quadruped.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Africa<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Late Eocene to Early Oligocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 16pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Parapithecidae<sup>3<\/sup><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Apidium<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Medium size. Retention of three premolars per quadrant. Rounded molars and premolars with large central cusps. Adaptations for leaping in the lower limb.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Africa<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Late Eocene to Late Oligocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 16pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Proteopithecidae<sup>4<\/sup><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Proteopithecus<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Small size. Retention of three premolars per quadrant. Arboreal quadrupeds that ate fruit.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Africa<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Late Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 16pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Oligopithecidae<sup>5<\/sup><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Catopithecus<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Small size. Skull has postorbital septum and unfused mandible. Deep jaws. Diet of fruits. Generalized quadruped.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Africa<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Late Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 16pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Eosimiidae<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Eosimias<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Deep jaw with vertical unfused symphysis. Pointed incisors and canines. Crowded premolars.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Asia<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle Eocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 16pt\">\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Amphipithecidae<sup>6<\/sup><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\"><em>Pondaungia<\/em><\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Deep jaws. Molars generally rounded with wide basins.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Asia<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt 0pt 5.4pt;border: solid #000000 0.5pt\">\n<p class=\"import-Normal\">Middle Eocene to Early Oligocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table3-R\" style=\"height: 1pt\">\n<td class=\"Table3-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\" colspan=\"4\">\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\n<p class=\"import-Normal\"><sup>2<\/sup> See Gebo and Simons 1987 and Simons et al. 2007.<\/p>\n<p class=\"import-Normal\"><sup>3<\/sup> See Feagle and Simons 1995 and Simons 2001.<\/p>\n<p class=\"import-Normal\"><sup>4<\/sup> See Simons and Seiffert 1999.<\/p>\n<p class=\"import-Normal\"><sup>5<\/sup> See Simons and Rasmussen 1996.<\/p>\n<p class=\"import-Normal\"><sup>6<\/sup> See Kay et al. 2004.<\/p>\n<\/td>\n<td class=\"Table3-C\" style=\"border-top: solid #000000 0.5pt;border-right: none #000000 0pt;border-bottom: none #000000 0pt;border-left: none #000000 0pt;padding: 0pt 5.4pt 0pt 5.4pt\">\n<p class=\"import-Normal\">\n<\/td>\n<\/tr>\n<tr>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p class=\"import-Normal\">Unfortunately for the adapoid hypothesis, most of the shared features listed above probably emerged independently in the two groups as adaptations to a diet of hard and\/or tough foods. For example, fusion of the mandibular symphysis likely evolved as a means to strengthen the jaw against forces that would pull the two halves away from each other, in the context of active chewing muscles on both sides of the head generating great bite forces. This context would also favor the development of robust jaws, large chewing muscles, shorter faces, and some other features shared by some adapoids and some anthropoids.<\/p>\n<p class=\"import-Normal\">As older and more plesiomorphic anthropoids were found in the Fayum Basin, it became clear that the earliest anthropoids from Africa did not possess these features of jaw robusticity (Seiffert et al. 2009). Furthermore, many adapoids never evolved these features. Fusion of the mandibular symphysis in adapoids is actually quite different from that in anthropoids and probably occurred during juvenile development in the former (Beecher 1983; Ravosa 1996). Eventually, the adapoid origin hypothesis fell out of favor among most paleoanthropologists, although the description of <em>Darwinius<\/em> is a recent revival of that idea (Franzen et al. 2009; but see Seiffert et al. 2009, Williams et al. 2010b).<\/p>\n<h4 class=\"import-Normal\"><em>Omomyoid Origin Hypothesis<\/em><\/h4>\n<p class=\"import-Normal\">Similarities in cranial and hindlimb morphology between some omomyoids and extant tarsiers have led to the suggestion that tarsiers arose from some kind of omomyoid. In particular, <em>Necrolemur<\/em> has many features in common with tarsiers, as does the North American <em>Shoshonius<\/em>, which is known from a few beautifully preserved (although distorted) crania. Tarsiers and <em>Shoshonius <\/em>share exclusively some features of the base of the cranium; however, <em>Shoshonius<\/em> does not have any sign of postorbital closure, and it lacks the bony ear tube of tarsiers. Nevertheless, some of the resemblances between some omomyoids and tarsiers suggest that tarsiers might have originated from within the Omomyoidea (Beard 2002; Beard and MacPhee 1994). In this scenario, although living tarsiers and living anthropoids might be sister taxa, they might have evolved from different omomyoids, possibly separated from each other by more than 50 million years of evolution, or from anthropoids evolved from some non-omomyoid fossil group. The arguments against the omomyoid origin hypothesis are essentially the arguments <em>for<\/em> the tarsier origin hypothesis (see below). Namely, tarsiers and anthropoids share many features (especially of the soft tissues) that must have been retained for many millions of years or must have evolved convergently in the two groups. Furthermore, a key hard-tissue feature shared between the two extant groups, the postorbital septum, was not present in any omomyoid. Therefore, that feature must have arisen convergently in the two extant groups or must have been lost in omomyoids. Neither scenario is very appealing, although recent arguments for <strong>convergent evolution<\/strong> of the postorbital septum in tarsiers and anthropoids have arisen from embryology and histology of the structure (DeLeon et al. 2016).<\/p>\n<h4 class=\"import-Normal\"><em>Tarsier Origin Hypothesis<\/em><\/h4>\n<p class=\"import-Normal\">Several paleoanthropologists have suggested that there is a relationship between tarsiers and anthropoids to the exclusion of omomyoids and adapoids (e.g., Cartmill and Kay 1978; Ross 2000; Williams and Kay 1995). Tarsiers and anthropoids today share several traits, including many soft-tissue features related to the olfactory system (e.g., the loss of a hairless external nose and loss of the median cleft running from the nose to the mouth, as possessed by strepsirrhines), and aspects of the visual system (e.g., the loss of a reflective layer at the back of the eye, similarities in carotid circulation to the brain, and mode of placentation). Unfortunately, none of these can be assessed directly in fossils. Some bony similarities between tarsiers and anthropoids include an extra air-filled chamber below the middle ear cavity, reduced bones within the nasal cavity, and substantial postorbital closure; these can be assessed in fossils, but the distribution of these traits in omomyoids does not yield clear answers. Furthermore, several similarities between tarsiers and anthropoids are probably due to similarities in sensory systems, which might have evolved in parallel for ecological reasons. Although early attempts to resolve the crown primates with molecular data were sometimes equivocal or in disagreement with one another, more recent analyses (including those of short interspersed elements) suggest that tarsiers and anthropoids are sister groups to the exclusion of lemurs and lorises (Williams et al. 2010a). However, this does not address omomyoids, all of which are far too ancient for DNA extraction.<\/p>\n<p class=\"import-Normal\">The above three hypotheses are not the only possibilities for anthropoid origins. It may be that anthropoids are neither the closest sister group of tarsiers, nor evolved from adapoids or omomyoids. In recent years, two new groups of Eocene Asian primates have been implicated in the origin of anthropoids: the eosimiids and the amphipithecids. It is possible that one or the other of these two groups gave rise to anthropoids. Regardless of the true configuration of the tree for crown primates, the three major extant groups probably diverged from each other quite long ago (Seiffert et al. 2004).<\/p>\n<h3 class=\"import-Normal\"><strong>Early Anthropoid Fossils in Africa<\/strong><\/h3>\n<figure style=\"width: 526px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image7-2.jpg\" alt=\"People digging in a sandy desert.\" width=\"526\" height=\"352\" \/><figcaption class=\"wp-caption-text\">Figure 9.15: Egyptian workers sweeping Quarry I in the Fayum Basin (2004). This technique, called wind harvesting, removes the desert crust and permits wind to blow out fine sediment and reveal fossils. Credit: <a class=\"rId66\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Egyptian workers sweeping Quarry I in the Fayum Basin (2004, Figure 8.12)<\/a> by Jonathan M. G. Perry is under a <a class=\"rId67\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<figure style=\"width: 280px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image14-2.jpg\" alt=\"A person using a tool to expose bone in sand.\" width=\"280\" height=\"423\" \/><figcaption class=\"wp-caption-text\">Figure 9.16: Elwyn Laverne Simons excavating Aegyptopithecus in the Fayum Basin. Credit: <a class=\"rId69\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Elwyn Laverne Simons in the Fayum Basin (Figure 8.13)<\/a> used by permission of the <a class=\"rId70\" href=\"https:\/\/lemur.duke.edu\/\">Duke Lemur Center,<\/a> Division of Fossil Primates, is under a <a class=\"rId71\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">The classic localities yielding the greatest wealth of early anthropoid fossils are those from the Fayum Basin in Egypt (Simons 2008; Figure 9.15). The Fayum is a veritable oasis of fossil primates in an otherwise spotty early Tertiary African record. Since the 1960s, teams led by E. L. Simons have discovered several new species of early anthropoids, some of which are known from many parts of the skeleton and several individuals (Figure 9.16).<\/p>\n<p class=\"import-Normal\">The Fayum Jebel Qatrani Formation and Birket Qarun Formation between them have yielded a remarkable array of terrestrial, arboreal, and aquatic mammals. These include ungulates, bats, sea cows, elephants, hyraces, rodents, whales, and primates. Also, many other vertebrates, like water birds, were present. The area at the time of deposition (Late Eocene through Early Oligocene) was probably very wet, with slow-moving rivers, standing water, swampy conditions, and lots of trees (see Bown and Kraus 1988). In short, it was an excellent place for primates.<\/p>\n<h4 class=\"import-Normal\"><em>General Morphology of Anthropoids<\/em><\/h4>\n<p class=\"import-Normal\">The anthropoids known from the Fayum (and their close relatives from elsewhere in East Africa and Afro-Arabia) bear many of the anatomical hallmarks of extant anthropoids; however, there are plesiomorphic forms in several families that lack one or more anthropoid traits. All Fayum anthropoids known from skulls possess postorbital closure, most had fused mandibular symphyses, and most had ring-like <strong>ectotympanic<\/strong>  bones. Tooth formulae were generally either 2.1.3.3 or 2.1.2.3. Fayum anthropoids ranged in size from the very small <em>Qatrania<\/em> and <em>Biretia <\/em>(less than 500 g) to the much-larger <em>Aegyptopithecus<\/em> (approximately 7 kg; 15 lbs.). Fruit was probably the main component of the diet for most or all of the anthropoids, with some of them supplementing with leaves (Kay and Simons 1980; Kirk and Simons 2001; Teaford et al. 1996). Most Fayum anthropoids were probably diurnal above-branch quadrupeds. Some of them (e.g., <em>Apidium<\/em>; see Figure 9.14) were probably very good leapers (Gebo and Simons 1987), but none show specializations for gibbon-style suspensory locomotion. Some of the Fayum anthropoids are known from hundreds of individuals, permitting the assessment of individual variation, sexual dimorphism, and in some cases growth and development. The description that follows provides greater detail for the two best known Fayum anthropoid families, the Propliopithecidae and the Parapithecidae; the additional families are summarized briefly.<\/p>\n<h4 class=\"import-Normal\"><em>Fayum Anthropoid Families<\/em><\/h4>\n<p class=\"import-Normal\">The Propliopithecidae (see Figure 9.14) include the largest anthropoids from the fauna, and they are known from several crania and some postcranial elements. They have been suggested to be stem catarrhines, although perhaps near the split between catarrhines and platyrrhines. The best known propliopithecid is <em>Aegyptopithecus<\/em>, known from many teeth, crania, and postcranial elements (Figure 9.17) .<\/p>\n<figure style=\"width: 431px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image4-2-1.jpg\" alt=\"Two animal skull side views.\" width=\"431\" height=\"281\" \/><figcaption class=\"wp-caption-text\">Figure 9.17: Female (left) and male (right) skull material for Aegyptopithecus zeuxis. The mandibles are not associated with the crania. Credit: <a href=\"https:\/\/www.pnas.org\/doi\/full\/10.1073\/pnas.0703129104#supplementary-materials\">Female and male cranium of A. zeuxi (03129Fig5, Supporting Information)<\/a> by Elwyn L. Simons, Erik R. Seiffert, Timothy M. Ryan, and Yousry Attia. 2007. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America<\/a> 104 (21): 8731\u20138736. Copyright (2007) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a><\/figcaption><\/figure>\n<p class=\"import-Normal\">Parapithecidae are an extremely abundant and unusual family of anthropoids from the Fayum. The parapithecid <em>Apidium<\/em> is known from many jaws with teeth, crushed and distorted crania, and several skeletal elements. <em>Parapithecus<\/em> is known from cranial material including a beautiful, undistorted cranium. This genus shows extreme reduction of the incisors, including complete absence of the lower incisors in <em>P. grangeri <\/em>(Simons 2001). This trait is unique among primates. Parapithecids were once thought to be the ancestral stock of platyrrhines; however, their platyrrhine-like features are probably ancestral retentions, so the most conservative approach is to consider them stem anthropoids.<\/p>\n<p class=\"import-Normal\">The Proteopithecidae were small frugivores that probably mainly walked along horizontal branches on all fours. They are considered stem anthropoids. The best known genus, <em>Proteopithecus<\/em>, is represented by dentitions, crania, and postcranial elements.<\/p>\n<p class=\"import-Normal\">The Oligopithecidae share a mixture of traits that makes them difficult to classify more specifically within anthropoids. The best known member, <em>Catopithecus<\/em>, is known from crania that demonstrate a postorbital septum and from mandibles that lack symphyseal fusion. They share the catarrhine tooth formula of 2.1.2.3 and have a canine honing complex that involves the anterior lower premolar. The postcranial elements known for the group suggest generalized arboreal quadrupedalism. The best known member, <em>Catopithecus<\/em>, is known from crania that demonstrate a postorbital septum and from mandibles that lack symphyseal fusion (Simons and Rasmussen 1996). The jaws are deep, with broad muscle attachment areas and crested teeth. <em>Catopithecus<\/em> was probably a little less than a kilogram in weight.<\/p>\n<p class=\"import-Normal\">Other genera of putative anthropoids from the Fayum include the very poorly known <em>Arsinoea<\/em>, the contentious <em>Afrotarsius<\/em>, and the enigmatic <em>Nosmips<\/em>. The last of these possesses traits of several major primate <strong>clades<\/strong> and defies classification (Seiffert et al. 2010).<\/p>\n<h3 class=\"import-Normal\"><strong>Early Anthropoid Fossils in Asia<br style=\"clear: both\" \/><\/strong><\/h3>\n<p class=\"import-Normal\">For the last half of the 1900s, researchers believed that Africa was the unquestioned homeland of early anthropoids (see Fleagle and Kay 1994). However, two very different groups of primates from Asia soon began to change that. One was an entirely new discovery (Eosimiidae), and the other was a poorly known group discovered decades prior (Amphipithecidae). Soon, attention on anthropoid origins began to shift eastward (see Ross and Kay 2004; Simons 2004). If anthropoids arose in Asia instead of Africa, then this implies that the African early anthropoids either emigrated from Asia or evolved their anthropoid traits in parallel with living anthropoids.<\/p>\n<h4 class=\"import-Normal\"><em>Eosimiids<\/em><\/h4>\n<p class=\"import-Normal\">First described in the 1990s, the eosimiids are best represented by <em>Eosimias <\/em>(see Figure 9.14; Figure 9.18). This tiny \u201cdawn monkey\u201d is known from relatively complete jaws with teeth, a few small fragments of the face, and some postcranial elements (Beard et al. 1994; Beard et al. 1996; Gebo et al. 2000). <em>Eosimias<\/em> (along with the other less-well-known genera in its family) bears some resemblance to tarsiers as well as anthropoids. Unfortunately, no good crania are known for this family, and the anatomy of, for example, the posterior orbital margin could be very revealing as to higher-level relationships.<\/p>\n<figure style=\"width: 550px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image16-1-1.jpg\" alt=\"Red-colored lower jaw of an animal.\" width=\"550\" height=\"232\" \/><figcaption class=\"wp-caption-text\">Figure 9.18: Cast of the right half of the mandible of Eosimias centennicus, type specimen. The white scale bar is 1 cm long. Credit: <a class=\"rId74\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Cast of the right half of the mandible of <\/a><a class=\"rId75\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Eosimias centennicus <\/em><\/a><a class=\"rId76\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">(Figure 8.15),<\/a> type specimen, from K. D. Rose cast collection, photo by Jonathan M. G. Perry is under a <a class=\"rId77\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h4 class=\"import-Normal\"><em>Amphipithecids<\/em><\/h4>\n<p class=\"import-Normal\">Amphipithecids are small- to medium-size primates (up to 10 kg; 22 lbs.). Most are from the Eocene Pondaung Formation in Myanmar (Early\u2013Middle Eocene), but one genus is known from Thailand. Some dental similarities with anthropoids were noted early on, such as deep jaws and wide basins that separate low molar cusps. The best known genera were <em>Pondaungia<\/em> and <em>Amphipithecus <\/em>(Ciochon and Gunnell 2002; see Figure 9.14). Another amphipithecid, <em>Siamopithecus<\/em> from Thailand, has very rounded molars and was probably a seed-eater (Figure 9.19). In addition to teeth and jaws, some cranial fragments, ankle material, and ends of postcranial bones have been found for <em>Pondaungia<\/em>. There are important resemblances between the postcranial bones of <em>Pondaungia<\/em> and those of adapoids, suggesting adapoid affinities for the amphipithecidae. This would imply that the resemblances with anthropoids in the teeth are convergent, based on similarities in diet (see Ciochon and Gunnell 2002). Unfortunately, the association between postcranial bones and teeth is not definite. With other primates in these faunas (including eosimiids), one cannot be certain that the postcranial bones belong with the teeth. Some researchers suggest that some bones belong to a sivaladapid (or asiadapid) and others to an early anthropoid (Beard et al. 2007; Marivaux et al. 2003). Additional well-associated material of amphipithecids would help to clear up this uncertainty.<\/p>\n<figure style=\"width: 505px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image15-2.jpg\" alt=\"Four casts of jawbone fragments with teeth.\" width=\"505\" height=\"368\" \/><figcaption class=\"wp-caption-text\">Figure 9.19: Casts of representative amphipithecid material. A. Pondaungia cotteri right lower jaw fragment with m2 and m3. B. Siamopithecus eocaenus right upper jaw fragment with p4-m3. C. S. eocaenus right lower jaw fragment with partial m1, m2, and m3 in lateral view. D. Same as in C but occlusal view. White scale bars are 1 cm long. Credit: <a class=\"rId79\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Casts of representative amphipithecid material (Figure 8.16)l<\/a> from K. D. Rose cast collection, photo by Jonathan M. G. Perry is under a <a class=\"rId80\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Platyrrhine Dispersal to South America<\/strong><\/h3>\n<p class=\"import-Normal\">Today there is an impressive diversity of primates in South and Central America. These are considered to be part of a single clade, the Platyrrhini. Primates colonized South America sometime in the Eocene from an African source. In the first half of the 20th century, the source of platyrrhines was a matter of major debate among paleontologists, with some favoring a North American origin (e.g., Simpson 1940).<\/p>\n<p class=\"import-Normal\">Part of the reason for this debate is that South America was an island in the Eocene. Primates needed to cross open ocean to get there from either North America or Africa, although the distance from the former was shorter. Morphology yields clues to platyrrhine origins. The first known primates in South America have more in common morphologically with African primates than with North American ones. At the time, anthropoids were popping up in North Africa, whereas the only euprimates in North America were adapoids and omomyoids. Despite lacking a bony ear tube, early platyrrhines shared a great deal with other anthropoids, including full postorbital closure and fusion of the mandibular symphysis.<\/p>\n<p class=\"import-Normal\">The means by which a population of small North African primates managed to disperse across the Atlantic and survive to colonize South America remains a mystery. The most plausible scenario is one of rafting. That is, primates must have been trapped on vegetation that was blown out to sea by a storm. The vegetation then became a sort of life raft, which eventually landed ashore, dumping its passengers in South America. Rodents probably arrived in South America in the same way (Antoine et al. 2012).<\/p>\n<p class=\"import-Normal\">Once ashore, platyrrhines must have crossed South America fairly rapidly because the earliest-known primates from that continent are from Peru (Bond et al. 2015). Soon after that, platyrrhines were in Bolivia, namely <em>Branisella<\/em>. By the Miocene, platyrrhines were living in extreme southern Argentina and were exploiting a variety of feeding niches. The Early Miocene platyrrhines were all somewhat plesiomorphic in their morphology, but some features that likely arose by ecological convergence suggest (to some) relationships with extant platyrrhine families. This has led to a lively debate about the pattern of primate evolution in South America (Kay 2015; Kay and Fleagle 2010; Rosenberger 2010). By the Middle Miocene, clear representatives of modern families were present in a diverse fauna from La Venta, Colombia (Wheeler 2010). The Plio-Pleistocene saw the emergence of giant platyrrhines as well as several taxa of platyrrhines living on Caribbean islands (Cooke et al. 2016).<\/p>\n<p class=\"import-Normal\">The story of platyrrhines seems to be one of amazing sweepstakes dispersal, followed by rapid diversification and widespread geographic colonization of much of South America. After that, dramatic extinctions resulted in the current, much-smaller geographic distribution of platyrrhines. These extinctions were probably caused by changing climates, leading to the contraction of forests. Platyrrhines dispersed to the Caribbean and to Central America, with subsequent extinctions in those regions that might have been related to interactions with humans. Unlike anthropoids of Africa and Asia, platyrrhines do not seem to have evolved any primarily terrestrial forms and so have always been highly dependent on forests.<\/p>\n<div class=\"textbox\">\n<h2 class=\"import-Normal\">Special Topic: Jonathan Perry and Primates of the Extreme South<\/h2>\n<p class=\"import-Normal\">Many primates are very vulnerable to ecological disturbance because they are heavily dependent on fruit to eat and trees to live in. This is one reason why so many primates are endangered today and why many of them went extinct due to climatic and vegetational changes in the past. I (Jonathan Perry) have conducted paleontological research focusing on primates that lived on the edge of their geographic distribution. This research has taken me to extreme environments in the Americas: southern Patagonia, the Canadian prairies, western Wyoming, and the badlands of eastern Oregon.<\/p>\n<p class=\"import-Normal\">Santa Cruz Province in Argentina is as far south as primates have ever lived. The Santa Cruz fauna of the Miocene has yielded a moderate diversity of platyrrhines, each with slightly different dietary adaptations. These include <em>Homunculus<\/em>, first described by Florentino Ameghino in 1891 (Figure 9.20). Recent fieldwork by my colleagues and I in Argentina has revealed several skulls of <em>Homunculus <\/em>as well as many parts of the skeleton (Kay et al. 2012). The emerging profile of this extinct primate is one of a dedicated arboreal quadruped that fed on fruits and leaves. Many of the foods eaten by <em>Homunculus<\/em> must have been very tough and were probably covered and impregnated with grit; we suspect this because the cheek teeth are very worn down, even in young individuals, and because the molar tooth roots were very large, presumably to resist strong bite forces (Perry et al. 2010, 2014).<\/p>\n<figure style=\"width: 497px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image9-2.jpg\" alt=\"An animal skull, a partial skull, and a fossil jaw with teeth.\" width=\"497\" height=\"634\" \/><figcaption class=\"wp-caption-text\">Figure 9.20: Representative specimens of Homunculus patagonicus. A. Adult cranium in lateral view. B. Adult cranium surface reconstructed from microCT scans, with the teeth segmented out. C. Juvenile cranium. White scale bars are 1cm long. Credit: <a class=\"rId82\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Representative specimens of <\/a><a class=\"rId83\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\"><em>Homunculus patagonicus <\/em><\/a><a class=\"rId84\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">(Figure 8.17)<\/a> photo by Jonathan M. G. Perry is under a <a class=\"rId85\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">I began working in Argentina while a graduate student at Duke University. I participated as a field assistant in a team led by my Ph.D. advisor, Richard F. Kay, and Argentine colleagues Sergio F. Vizca\u00edno and M. Susana Bargo. Most of the localities examined belong to a suite of beach sites known since the 1800s and visited by many field parties from various museums in the early 1900s. Since 2003, our international team of paleontologists from the U.S. and Argentina has visited these localities every single year (Figure 9.21). Over time, new fossils and new students have led to new projects and new approaches, including the use of microcomputed tomography (microCT) to visualize and analyze internal structures of the skeleton.<\/p>\n<figure style=\"width: 491px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image23.jpg\" alt=\"Sandy rocky coastline. People digging on a grassy hillside.\" width=\"491\" height=\"561\" \/><figcaption class=\"wp-caption-text\">Figure 9.21: Field localities in Argentina and Canada. A. Ca\u00f1adon Palos locality, coastal Santa Cruz Province, Argentina. B. Swift Current Creek locality, southwest Saskatchewan, Canada. Credits: A. <a class=\"rId87\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Ca\u00f1adon Palos Field Locality in Argentina<\/a> by Jonathan M. G. Perry is under a <a class=\"rId88\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. B. <a class=\"rId89\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Swift Current Creek locality, Saskatchewan, Canada<\/a> by Jonathan M. G. Perry is under a <a class=\"rId90\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<\/div>\n<h2 class=\"import-Normal\">Planet of Apes<\/h2>\n<h3 class=\"import-Normal\"><strong>Geologic Activity and Climate Change in the Miocene<\/strong><\/h3>\n<p class=\"import-Normal\">The Miocene Epoch was a time of mammalian diversification and extinction, global climate change, and ecological turnover. In the Miocene, there was an initial warming trend across the globe with the expansion of subtropical forests, followed by widespread cooling and drying with the retreat of tropical forests and replacement with more open woodlands and eventually grasslands. It was also a time of major geologic activity. On one side of the globe, South America experienced the rise of the Andes Mountains. On the other side, the Indian subcontinent collided with mainland Asia, resulting in the rise of the Himalayan Mountains. In Africa, volcanic activity promoted the development of the East African Rift System. Critical to the story of ape evolution was the exposure of an intercontinental landbridge between East Africa and Eurasia, permitting a true planet of apes (Figure 9.22).<\/p>\n<figure id=\"attachment_277\" aria-describedby=\"caption-attachment-277\" style=\"width: 580px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-273\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image21-3-e1691792198797.png\" alt=\"Map of world with gray continents.\" width=\"580\" height=\"335\" \/><figcaption id=\"caption-attachment-277\" class=\"wp-caption-text\">Figure 9.22: Map of the world in the Miocene, highlighting fossil ape localities across Africa, southern Europe, and southern Asia. Credit: <a class=\"rId92\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-10\/\">Miocene Map with Fossil Ape Localities (Figure 8.19)<\/a> original to <a class=\"rId93\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Elyssa Ebding at <a class=\"rId94\" href=\"https:\/\/www.csuchico.edu\/geop\/geoplace\/index.shtml\">GeoPlace, California State University, Chico<\/a> is under a <a class=\"rId95\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Localities based on Fleagle 2013, 311.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Geographic Distribution: Africa, Asia, Europe<\/strong><\/h3>\n<p class=\"import-Normal\">The world of the Miocene had tremendous ape diversity compared to today. The earliest records of fossil apes are from Early Miocene deposits in Africa. However, something dramatic happened around 16 million years ago. With the closure of the ancient Tethys Sea, the subsequent exposure of the <em>Gomphotherium<\/em> Landbridge, and a period of global warming, the Middle\u2013Late Miocene saw waves of emigration of mammals (including primates) out of Africa and into Eurasia, with evidence of later African re-entry for some (Harrison 2010). Some of the mammals that dispersed from Africa to Eurasia and back were apes. Though most of these early apes left no modern descendants, some of them gave rise to the ancestors of modern apes\u2014including <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_280_800\">hominins<\/a><\/strong> (Figure 9.23).<\/p>\n<figure style=\"width: 560px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image20-1.jpg\" alt=\"Miocene apes set against a geologic time scale.\" width=\"560\" height=\"796\" \/><figcaption class=\"wp-caption-text\">Figure 9.23: Representative Miocene apes set against a geologic time scale. Credit: <a href=\"https:\/\/www.pnas.org\/content\/108\/14\/5554\">Range chart for Miocene hominoids of Western Eurasia (Figure 3)<\/a> by Isaac Casanovas-Vilar, David M. Alba, Miguel Garc\u00e9s, Josep M. Robles, and Salvador Moy\u00e0-Sol\u00e0. 2011. <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">Proceedings of the National Academy of Sciences of the United States of America<\/a> 108 (14): 5554-5559. Copyright (2011) National Academy of Sciences. Image <a href=\"https:\/\/www.pnas.org\/about\/rights-permissions\">is used for non-commercial and educational purposes as outlined by PNAS.<\/a><\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Where Are the Monkeys? Diversity in the Miocene<\/strong><\/h3>\n<p class=\"import-Normal\">Whereas the Oligocene deposits in the Fayum of Egypt have yielded the earliest-known catarrhine fossils, the Miocene demonstrates some diversification of Cercopithecoidea. However, compared to the numerous and diverse Miocene apes (see below), monkeys of the Miocene are very rare and restricted to a single extinct family, the Victoriapithecidae (Figure 9.24). This family contains the earliest definite cercopithecoids. These monkeys are found from northern and eastern Africa between 20 million and 12.5 million years ago (Miller et al. 2009). The best known early African monkey is <em>Victoriapithecus <\/em>(Figure 9.25), a small-bodied (approximately 7 kg; 15 lbs.), small-brained monkey. <strong>Bilophodonty<\/strong>, known to be a hallmark of molar teeth of modern cercopithecoid, was present to some extent in Victoriapithecids. <em>Victoriapithecus<\/em> has been reconstructed as being more frugivorous and perhaps spent more time on the ground (terrestrial locomotion) than in the trees (arboreal locomotion; Blue et al. 2006). The two major groups of cercopithecoids today are cercopithecines and colobines. The earliest records demonstrating clear members of each of these two groups are at the end of the Miocene. Examples include the early colobine <em>Microcolobus<\/em> from Kenya and the early cercopithecine <em>Pliopapio<\/em> from Ethiopia.<\/p>\n<div style=\"text-align: left\">\n<table class=\"aligncenter\" style=\"width: 473.25pt;height: 349px\">\n<caption>Figure 9.24: Some families of later anthropoids with example genera and traits: a table. Credit: Late anthropoids table original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Jonathan M. G. Perry and Stephanie L. Canington is under a <a class=\"rId100\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. Content derived from Fleagle 2013.<\/caption>\n<thead>\n<tr style=\"height: 25pt\">\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 119.35px\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Family<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 103.417px\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Genera<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 191.65px\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Morphology<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 67.3667px\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Location<\/strong><\/p>\n<p>&nbsp;<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 60px;width: 73.2167px\">\n<p class=\"import-Normal\" style=\"text-align: center\"><strong>Age<\/strong><sup><strong>1<\/strong><\/sup><\/p>\n<p>&nbsp;<\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr class=\"Table4-R\" style=\"height: 18pt\">\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 119.35px\">\n<p class=\"import-Normal\">Victoriapithecidae<sup>2<\/sup><\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 103.417px\">\n<p class=\"import-Normal\"><em>Victoriapithecus<\/em><\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 191.65px\">\n<p class=\"import-Normal\">Long, sloping face. Round, narrowly spaced orbits. Deep cheek bones. Well-developed sagittal crest.<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 67.3667px\">\n<p class=\"import-Normal\">Africa<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 77px;width: 73.2167px\">\n<p class=\"import-Normal\">Early to Middle Miocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table4-R\" style=\"height: 16pt\">\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 119.35px\">\n<p class=\"import-Normal\">Proconsulidae<sup>3<\/sup><\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 103.417px\">\n<p class=\"import-Normal\"><em>Proconsul<\/em><\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 191.65px\">\n<p class=\"import-Normal\">Short face. Generalized dentition. Arboreal quadruped. Probably tailless.<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 67.3667px\">\n<p class=\"import-Normal\">Africa and Arabia<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 61px;width: 73.2167px\">\n<p class=\"import-Normal\">Early to Middle Miocene<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table4-R\" style=\"height: 16pt\">\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 119.35px\">\n<p class=\"import-Normal\">Pongidae<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 103.417px\">\n<p class=\"import-Normal\"><em>Gigantopithecus<\/em><\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 191.65px\">\n<p class=\"import-Normal\">Largest primate ever. Deep jaws and low rounded molars.<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 67.3667px\">\n<p class=\"import-Normal\">Asia<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"vertical-align: middle;padding: 0pt 5.4pt;border: 0.5pt solid #000000;height: 46px;width: 73.2167px\">\n<p class=\"import-Normal\">Miocene to Present<\/p>\n<\/td>\n<\/tr>\n<tr class=\"Table4-R\" style=\"height: 1pt\">\n<td class=\"Table4-C\" style=\"border-color: #000000;border-style: solid none none;border-width: 0.5pt 0pt 0pt;padding: 0pt 5.4pt;height: 90px;width: 526.983px\" colspan=\"4\">\n<p class=\"import-Normal\"><sup>1<\/sup> Derived from Fleagle 2013.<\/p>\n<p class=\"import-Normal\"><sup>2<\/sup> See Benefit and McCrossin 1997 and Fleagle 2013.<\/p>\n<p class=\"import-Normal\"><sup>3<\/sup> See Begun 2007.<\/p>\n<\/td>\n<td class=\"Table4-C\" style=\"border-color: #000000;border-style: solid none none;border-width: 0.5pt 0pt 0pt;padding: 0pt 5.4pt;height: 90px;width: 73.2167px\">\n<p class=\"import-Normal\">\n<\/td>\n<\/tr>\n<tr style=\"height: 15px\">\n<td style=\"height: 15px;width: 121.283px\"><\/td>\n<td style=\"height: 15px;width: 105.35px\"><\/td>\n<td style=\"height: 15px;width: 193.583px\"><\/td>\n<td style=\"height: 15px;width: 69.3px\"><\/td>\n<td style=\"height: 15px;width: 74.65px\"><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<h3><\/h3>\n<h3><\/h3>\n<h3><\/h3>\n<h3 class=\"import-Normal\"><strong>The Story of Us, the Apes<\/strong><\/h3>\n<h4 class=\"import-Normal\"><em>African Ape Diversity\u00a0<\/em><\/h4>\n<p class=\"import-Normal\">The Early Miocene of Africa has yielded around 14 genera of early apes (Begun 2003). Many of these taxa have been reconstructed as frugivorous arboreal quadrupeds (Kay 1977). One of the best studied of these genera is the East African <em>Proconsul<\/em> (Family Proconsulidae; see Figure 9.24). Several species have been described, with body mass reconstructions ranging from 17 to 50 kg (approximately 37\u2013110 lbs.). A paleoenvironmental study reconstructed the habitat of <em>Proconsul <\/em>to be a dense, closed-canopy tropical forest (Michel et al. 2014). No caudal vertebrae (tail bones) have been found in direct association with <em>Proconsul <\/em>postcrania, and the morphology of the sacrum is consistent with <em>Proconsul<\/em> lacking a tail (Russo 2016; Ward et al. 1991).<\/p>\n<p class=\"import-Normal\">Overall, the African ape fossil record in the Late Miocene is sparse, with seven fossil localities dating between eleven and five million years ago (Pickford et al. 2009). Nevertheless, most species of great apes live in Africa today. Where did the progenitors of modern African apes arise? Did they evolve in Africa or somewhere else? The paucity of apes in the Late Miocene of Africa stands in contrast to the situation in Eurasia. There, ape diversity was high. Furthermore, several Eurasian ape fossils show morphological affinities with modern hominoids (apes). Because of this, some paleoanthropologists suggest that the ancestors of modern African great apes recolonized Africa from Eurasia toward the end of the Miocene (Begun 2002). However, discoveries of Late Miocene hominoids like the Kenyan <em>Nakalipithecus<\/em> (9.9 million to 9.8 million years ago), the Ethiopian <em>Chororapithecus<\/em> (10.7 million to 10.1 million years ago), and the late-Middle Miocene Namibian <em>Otavipithecus<\/em> (13 million to 12 million years ago) fuel an alternative hypothesis\u2014namely that African hominoid diversity was maintained throughout the Miocene and that one of these taxa might, in fact, be the last common ancestor of extant African apes (Kunimatsu et al. 2007; Mocke et al. 2002). The previously underappreciated diversity of Late Miocene apes in Africa might be due to poor sampling of the fossil record in Africa.<\/p>\n<h4 class=\"import-Normal\"><em>Eurasian Ape Diversity<\/em><\/h4>\n<p class=\"import-Normal\">With the establishment of the <em>Gomphotherium<\/em> Landbridge (a result of the closure of the Eastern Mediterranean seaway; R\u00f6gl 1999), the Middle Miocene was an exciting time for hominoid radiations outside of Africa (see Figure 9.23). Eurasian hominoid species exploited their environments in many different ways in the Miocene. Food exploitation ranged from soft-fruit feeding in some taxa to hard-object feeding in others, in part owing to seasonal fluctuations and the necessary adoptions of fallback foods (DeMiguel et al. 2014). For example, the molars of <em>Oreopithecus bambolii<\/em> (Family Hominidae) have relatively long lower-molar shearing crests, suggesting that this hominoid was very folivorous (Ungar and Kay 1995). Associated with variation in diet, there is great variation in the degree to which cranial features (e.g., zygomatic bone or supraorbital tori) are developed across the many taxa (Cameron 1997); however, Middle Miocene fossils tend to exhibit relatively thick molar enamel and relatively robust jaws (Andrews and Martin 1991).<\/p>\n<p class=\"import-Normal\">In Spain, the cranium with upper dentition, part of a mandible, and partial skeleton of <em>Pliobates <\/em>(Family Pliobatidae), a small-bodied ape (4\u20135 kg; 9\u201311 lbs.), was discovered in deposits dating to 11.6 million years ago (Alba et al. 2015). It is believed to be a frugivore with a relative brain size that overlaps with modern cercopithecoids. The fossilized postcrania of <em>Pliobates<\/em> suggest that this ape might have had a unique style of locomotion, including the tendency to walk across the branches of trees with its palms facing downward and flexible wrists that permitted rotation of the forearm during climbing. However, the anatomy of the distal humerus differs from those of living apes in ways that suggest that <em>Pliobates<\/em> was less efficient at stabilizing its elbow while suspended (Benefit and McCrossin 2015). Two other recently described apes from Spain, <em>Pierolapithecus <\/em>and <em>Anoiapithecus<\/em>, are known from relatively complete skeletons. <em>Pierolapithecus<\/em> had a very projecting face and thick molar enamel as well as some skeletal features that suggest (albeit controversially) a less suspensory locomotor style than in extant apes (Moy\u00e0-Sol\u00e0 et al. 2004). In contrast to <em>Pierolapithecus<\/em>, the slightly younger <em>Anoiapithecus<\/em> has a very flat face (Moy\u00e0-Sol\u00e0 et al. 2009).<\/p>\n<p class=\"import-Normal\">Postcranial evidence for suspensory or well-developed orthograde behaviors in apes does not appear until the Late Miocene of Europe. Primary evidence supporting these specialized locomotor modes includes the relatively short lumbar vertebrae of <em>Oreopithecus <\/em>(Figure 9.26) and <em>Dryopithecus<\/em> (Maclatchy 2004). Further, fossil material of the lower torso of <em>O. bambolii <\/em>(which dates to the <em>Pan<\/em>-hominin divergence) conveys a higher degree of flexion-extension abilities in the lumbar region (lower back) than what is possible in extant apes. Additionally, the hindlimb of <em>O. bambolii <\/em>is suggested to have supported powerful hip adduction during climbing (Hammond et al. 2020). The Late Miocene saw the extinction of most of the Eurasian hominoids in an event referred to as the Vallesian Crisis (Agust\u00ed et al. 2003). Among the latest surviving hominoid taxa in Eurasia were <em>Oreopithecus<\/em> and <em>Gigantopithecus<\/em>, the latter of which held out until the Pleistocene in Asia and was probably even sympatric with <em>Homo erectus<\/em> (Cachel 2015).<\/p>\n<figure style=\"width: 436px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image8-2-1.jpg\" alt=\"Posterior view of ancient ape skeleton.\" width=\"436\" height=\"775\" \/><figcaption class=\"wp-caption-text\">Figure 9.26: Skeleton of Oreopithecus bambolii. Credit: <a class=\"rId107\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Oreopithecus_bambolii_1.JPG\">Oreopithecus bambolii 1<\/a> by <a class=\"rId108\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Ghedoghedo\">Ghedoghedo<\/a> is under a <a class=\"rId109\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/legalcode\">CC BY-SA 3.0 License<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>The Origins of Extant Apes<\/strong><\/h3>\n<p class=\"import-Normal\">The fossil record of the extant apes is somewhat underwhelming: it ranges from being practically nonexistent for some taxa (e.g., chimpanzees) to being a little better for others (e.g., humans). There are many possible reasons for these differences in fossil abundance, and many are associated with the environmental conditions necessary for the fossilization of bones. One way to understand the evolution of extant apes that is not so dependent on the fossil record is via molecular evolutionary analyses. This can include counting up the differences in the genetic sequence between two closely related species to estimate the amount of time since these species shared a common ancestor. This is called a molecular clock, and it is often calibrated using fossils of known absolute age that stand in for the last common ancestor of a particular clade. Molecular clock estimates have placed the Hylobatidae and Hominidae split between 19.7 million and 24.1 million years ago, the African ape and Asian ape split between 15.7 million and 19.3 million years ago, and the split of Hylobatidae into its current genera between 6.4 million and 8 million years ago (Israfil et al. 2011).<\/p>\n<h4 class=\"import-Normal\"><em>Small Ape Origins and Fossils<\/em><\/h4>\n<p class=\"import-Normal\">Unfortunately, the fossil record for the small (formerly \u201clesser\u201d) apes is meager, particularly in Miocene deposits. One possible early hylobatid is <em>Laccopithecus robustus<\/em>, a Late Miocene catarrhine from China (Harrison 2016). Although it does share some characteristics with modern gibbons and siamangs (including an overall small body size and a short face), <em>Laccopithecus<\/em> most likely represents a plesiomorphic stem catarrhine and is therefore distantly related to extant apes (Jablonski and Chaplin 2009). A more likely candidate for the hylobatid stem is another Late Miocene taxon from China, <em>Yuanmoupithecus xiaoyuan<\/em>. Interpretation of its phylogenetic standing, however, is complicated by contradicting dental features\u2014some of them quite plesiomorphic\u2014which some believe best place <em>Yuanmoupithecus<\/em> as a stem hylobatid (Harrison 2016). Recently, a Middle Miocene Indian fossil ape, <em>Kapi ramnagarensis<\/em>, has extended the fossil record of small apes by approximately five million years. Its teeth are suggestive of a shift to a more frugivorous diet and it is likely a stem hylobatid (Gilbert et al. 2020). The history of Hylobatidae becomes clearer in the Pleistocene, with fossils representing extant genera.<\/p>\n<h4 class=\"import-Normal\"><em>Great Ape Origins and Fossils<\/em><\/h4>\n<p class=\"import-Normal\">The most extensive fossil record of a modern great ape is that of our own genus, <em>Homo<\/em>. However, the evolutionary history of the Asian great ape, the orangutan (<em>Pongo<\/em>), is becoming clearer. Today, orangutans are found only on the islands of Borneo and Sumatra. However, Pleistocene-aged teeth, attributed to <em>Pongo<\/em>, have been found in Cambodia, China, Laos, Peninsular Malaysia, and Vietnam\u2014demonstrating the vastness of the orangutan\u2019s previous range (Ibrahim et al. 2013; Wang et al. 2014). <em>Sivapithecus <\/em>from the Miocene of India and Pakistan is represented by many specimens, including parts of the face. <em>Sivapithecus<\/em> is very similar to <em>Pongo<\/em>, especially in the face, and it probably is closely related to ancestral orangutans (Pilbeam 1982). Originally, jaws and teeth belonging to the former genus <em>Ramapithecus<\/em> were thought to be important in the origin of humans (Simons 1961), but now these are recognized as specimens of <em>Sivapithecus<\/em> (Kelley 2002). Postcranial bones of <em>Sivapithecus<\/em>, however, suggest a more generalized locomotor mode\u2014including terrestrial locomotion\u2014than seen in <em>Pongo <\/em>(Pilbeam et al. 1990). Stable carbon and oxygen isotope data from dental enamel have reconstructed the paleoecological space of <em>Sivapithecus <\/em>(as well as the contemporaneous Late Miocene pongine <em>Khoratpithecus<\/em>) within the canopies of forested habitats (Habinger et al. 2022).<\/p>\n<p class=\"import-Normal\">A probable close relative of <em>Sivapithecus <\/em>is the amazing <em>Gigantopithecus<\/em> (see Figure 9.24). Known only from teeth and jaws from China and India (e.g., Figure 9.27), this ape probably weighed as much as 270 kg (595 lbs.) and was likely the largest primate ever (Bocherens et al. 2017). Because of unique features of its teeth (including molarized premolars and patterns of wear) and its massive size, it has been reconstructed as a bamboo specialist, somewhat like the modern panda. Small silica particles (phytoliths) from grasses have been found stuck to the molars of <em>Gigantopithecus<\/em> (Ciochon et al. 1990). Recent studies evaluating the carbon isotope composition of the enamel sampled from <em>Gigantopithecus<\/em> teeth suggest that this ape exploited a wide range of vegetation, including fruits, leaves, roots, and bamboo (Bocherens et al. 2017). Its face is reminiscent of that of modern orangutans and it might belong in the same family, Pongidae (Kelley 2002).<\/p>\n<figure style=\"width: 488px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image12.jpg\" alt=\"Superior view of mandible and teeth.\" width=\"488\" height=\"533\" \/><figcaption class=\"wp-caption-text\">Figure 9.27: Cast of the mandible of Gigantopithecus blacki. Credit: <a class=\"rId111\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Gigantopithecus%20blacki%20mandible%20010112.jpg\">Gigantopithecus blacki mandible 010112<\/a> by <a class=\"rId112\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Wilson44691\">Wilson44691<\/a> is under a <a class=\"rId113\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/legalcode\">CC BY-SA 3.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">In Africa, the first fossil to be confidently attributed to <em>Pan<\/em>, and known to be the earliest evidence of a chimpanzee, was described based on teeth found in Middle Pleistocene deposits in the Eastern Rift Valley of Kenya (McBrearty and Jablonski 2005). Paleoenvironmental reconstructions of this locality suggest that this early chimpanzee was living in close proximity to early <em>Homo<\/em> in a closed-canopy wooded habitat. Similarly, fossil teeth and mandibular remains attributed to two species of Middle-Late Miocene apes\u2014<em>Chororapithecus abyssinicus<\/em> (from Ethiopia; Suwa et al. 2007) and <em>Nakalipithecus nakayamai<\/em> (from Kenya; Kunimatsu et al. 2007)\u2014have been suggested as basal members of the gorilla clade.<\/p>\n<p class=\"import-Normal\">While the deposits of Eastern Africa have yielded a profound record of our fossil hominin ancestors, the continent\u2019s rainforests remain a \u201cpalaeontological desert\u201d (Rosas et al. 2022). Clearly, more work is needed to fill in the large gaps in the fossil record of the nonhuman great apes. The twentieth century witnessed the discovery of many hominin fossils in East Africa, which have been critical for improving our understanding of human evolution. While twenty-first-century conservationists fight to prevent the extinction of the living great apes, perhaps efforts by twenty-first-century paleoanthropologists will yield the evolutionary story of these, our closest relatives.<\/p>\n<div class=\"textbox shaded\">\n<h2>Summary<\/h2>\n<p>While there are large gaps in the fossil records linking primates to early hominins, evolutionary trends make it clear that humans are one branch of the broader primate family tree. In this chapter we go over the major development that characterize primate evolution: enhanced vision, grasping hands and feet, greater reliance on social behavior, and increased brain complexity. It is these traits which distinguish primates from other mammals and furthermore, help define major subsections within the primate class, such as strepsirrhines, haplorhines, monkeys, apes, and ultimately hominins.<\/p>\n<p>Within this chapter, we also examine how anthropologists reconstruct these evolutionary relationships. Fossil evidence has provided key information about when and where different primates lived, while genetic data such as skeletal features allow researchers to understand how extinct species moved, ate, and interacted with their environments. Just as crucial are the influences of Earth\u2019s changing environments: continental drift, glacial cycles, and long-term climate shifts have repeatedly reshaped habitats, driving both extinctions and the emergence of new adaptive forms, including the emergence of our own human lineage.<\/p>\n<h2 class=\"import-Normal\">Review Questions<strong><br \/>\n<\/strong><\/h2>\n<ul>\n<li>Compare three major hypotheses about primate origins, making reference to each one\u2019s key ecological reason for primate uniqueness.<\/li>\n<li>Explain how changes in temperature, rainfall, and vegetation led to major changes in primate biogeography over the Early Tertiary.<\/li>\n<li>List some euprimate features that plesiadapiforms have and some that they lack.<\/li>\n<li>Contrast adapoids and omomyoids in terms of life habits.<\/li>\n<li>Describe one piece of evidence for each of the adapoid, omomyoid, and tarsier origin hypotheses for anthropoids.<\/li>\n<li>Discuss the biogeography of the origins of African great apes and orangutans using examples from the Miocene ape fossil record.<\/li>\n<\/ul>\n<\/div>\n<h2 class=\"import-Normal\">Key Terms<strong><br \/>\n<\/strong><\/h2>\n<p class=\"import-Normal\"><strong>Adapoidea<\/strong>: Order: Primates. One of the earliest groups of euprimates (true primates; earliest records from the early Eocene).<\/p>\n<p class=\"import-Normal\"><strong>A<\/strong><strong>daptive radiations<\/strong>: Rapid diversifications of single lineages into many species which may present unique morphological features in response to different ecological settings.<\/p>\n<p class=\"import-Normal\"><strong>Ancestral traits<\/strong>: Features that were inherited from a common ancestor and which remain (largely) unchanged.<\/p>\n<p class=\"import-Normal\"><strong>Anthropoids<\/strong>:Group containing monkeys and apes, including humans.<\/p>\n<p class=\"import-Normal\"><strong>Auditory bulla<\/strong>: The rounded bony floor of the middle ear cavity.<\/p>\n<p class=\"import-Normal\"><strong>Bilophodonty<\/strong>: Dental condition in which the cusps of molar teeth form ridges (or lophs) separated from each other by valleys (seen, e.g., in modern catarrhine monkeys).<\/p>\n<p class=\"import-Normal\"><strong>Catarrhines<\/strong>: Order: Primates; Suborder: Anthropoidea; Infraorder: Catarrhini. Group, with origins in Africa and Asia, that contains monkeys and apes, including humans.<\/p>\n<p class=\"import-Normal\"><strong>Clade<\/strong>:Group containing all of the descendants of a single ancestor. A portion of a phylogenetic tree represented as a bifurcation (node) in a lineage and all of the branches leading forward in time from that bifurcation.<\/p>\n<p class=\"import-Normal\"><strong>Convergent evolution<\/strong>: The independent evolution of a morphological feature in animals not closely related (e.g., wings in birds and bats).<\/p>\n<p class=\"import-Normal\"><strong>Crown<\/strong>: Smallest monophyletic group (clade) containing a specified set of extant taxa and all descendants of their last common ancestor.<\/p>\n<p class=\"import-Normal\"><strong>Diastema<\/strong>: Space between adjacent teeth.<\/p>\n<p class=\"import-Normal\"><strong>Diffuse coevolution<\/strong>: The ecological interaction between whole groups of species (e.g., primates) with whole groups of other species (e.g., fruiting trees).<\/p>\n<p class=\"import-Normal\"><strong>Ectotympanic<\/strong>: Bony ring or tube that holds the tympanic membrane (eardrum).<\/p>\n<p class=\"import-Normal\"><strong>Euprimates<\/strong>: Order: Primates. True primates or primates of modern aspect.<\/p>\n<p class=\"import-Normal\"><strong>Haplorhines<\/strong>: Group containing catarrhines, platyrrhines, and tarsiers.<\/p>\n<p class=\"import-Normal\"><strong>Hominins<\/strong>: Modern humans and any extinct relatives more closely related to us than to chimpanzees.<\/p>\n<p class=\"import-Normal\"><strong>Mandibular symphysis<\/strong>: Fibrocartilaginous joint between the left and right mandibular segments, located in the midline of the body.<\/p>\n<p class=\"import-Normal\"><strong>Omomyoidea<\/strong>: Order: Primates; Superfamily: Omomyoidea. One of the earliest groups of euprimates (true primates; earliest record in the early Eocene).<\/p>\n<p class=\"import-Normal\"><strong>Petrosal bone<\/strong>: The portion of the temporal bone that houses the inner ear apparatus.<\/p>\n<p class=\"import-Normal\"><strong>Plagiaulacoid<\/strong>: Dental condition where at least one of the lower cheek-teeth (molars or premolars) is a laterally compressed blade.<\/p>\n<p class=\"import-Normal\"><strong>Platyrrhines<\/strong>: Order: Primates; Suborder: Anthropoidea; Infraorder: Platyrrhini. Group containing monkeys found in the Americas.<\/p>\n<p class=\"import-Normal\"><strong>Plesiadapiforms<\/strong>: Order: Plesiadapiformes. Archaic primates or primate-like placental mammals (Early Paleocene\u2013Late Eocene).<\/p>\n<p class=\"import-Normal\"><strong>P<\/strong><strong>lesiomorphic<\/strong>: Having features that are shared by different groups which arose from a common ancestor.<\/p>\n<p class=\"import-Normal\"><strong>Stem<\/strong>: Taxa that are basal to a given crown group but are more closely related to the crown group than to the closest living sister taxon of the crown group.<\/p>\n<p class=\"import-Normal\"><strong>Strepsirrhines<\/strong>: Order: Primates; Suborder: Stresirrhini. Group containing lemurs, lorises, and galagos (does not include tarsiers).<\/p>\n<p class=\"import-Normal\"><strong>Toothcomb<\/strong>: Dental condition found in modern strepsirrhines in which the lower incisors and canines are laterally compressed and protrude forward at a nearly horizontal inclination. This structure is used in grooming.<\/p>\n<\/div>\n<div class=\"__UNKNOWN__\">\n<h2 class=\"import-Normal\">For Further Exploration<strong><br \/>\n<\/strong><\/h2>\n<p class=\"import-Normal\">Beard, Chris. 2004. <em>The Hunt for the Dawn Monkey: Unearthing the Origins of Monkeys, Apes, and Humans<\/em>. Berkeley: University of California Press.<\/p>\n<p class=\"import-Normal\">Begun, David R. 2010. \u201cMiocene Hominids and the Origins of the African Apes and Humans.\u201d <em>Annual Review of Anthropology<\/em> 39: 67\u201384.<\/p>\n<p class=\"import-Normal\">Fleagle, John G. 2013. <em>Primate Adaptation and Evolution.<\/em> Third edition. San Diego, CA: Academic Press.<\/p>\n<p class=\"import-Normal\">Gebo, Daniel L., ed. 1993. <em>Postcranial Adaptations in Nonhuman Primates<\/em>. Dekalb: Northern Illinois University Press.<\/p>\n<p class=\"import-Normal\">Godfrey, Laurie R., and William L. Jungers. 2002. \u201cQuaternary Fossil Lemurs.\u201d In <em>The Primate Fossil Record, <\/em>edited by Walter C. Hartwig, 97\u2013121. Cambridge: Cambridge University Press.<\/p>\n<p class=\"import-Normal\">Godinot, Marc. 2006. \u201cLemuriform Origins as Viewed from the Fossil Record.\u201d <em>Folia Primatologica<\/em> 77 (6): 446\u2013464.<\/p>\n<p class=\"import-Normal\">Kay, Richard F. 2018. \u201c100 Years of Primate Paleontology.\u201d <em>American Journal of Physical Anthropology<\/em> 165 (4): 652\u2013676.<\/p>\n<p class=\"import-Normal\">Marivaux, Laurent. 2006. \u201cThe Eosimiid and Amphipithecid Primates (Anthropoidea) from the Oligocene of the Bugti Hills (Balochistan, Pakistan): New Insight into Early Higher Primate Evolution in South Asia.\u201d <em>Palaeovertebrata, Montpellier <\/em>34 (1\u20132): 29\u2013109.<\/p>\n<p class=\"import-Normal\">Martin, R. D. 1990. <em>Primate Origins and Evolution<\/em><em>: A <\/em><em>Phylogenetic Reconstruction<\/em>. Princeton: Princeton University Press.<\/p>\n<p class=\"import-Normal\">Rose, Kenneth D., Marc Godinot, and Thomas M. Bown. 1994. \u201cThe Early Radiation of Euprimates and the Initial Diversification of Omomyidae.\u201d In <em>Anthropoid Origins: The Fossil Evidence, <\/em>edited by John G. Fleagle and Richard F. Kay, 1\u201328. New York: Plenum Press.<\/p>\n<p class=\"import-Normal\">Ross, Callum F. 1999. \u201cHow to Carry Out Functional Morphology.\u201d <em>Evolutionary Anthropology<\/em> 7 (6): 217\u2013222.<\/p>\n<p class=\"import-Normal\">Seiffert, Erik R. 2012. \u201cEarly Primate Evolution in Afro-Arabia.\u201d Evolutionary Anthropology: Issues, News, and Reviews 21(6): 239\u2013253.<\/p>\n<p class=\"import-Normal\">Szalay, Frederic S., and Eric Delson. 1979. Evolutionary History of the Primates. New York: Academic Press.<\/p>\n<p class=\"import-Normal\">Ungar, Peter S. 2002. \u201cReconstructing the Diets of Fossil Primates.\u201d In <em>Reconstructing Behavior in the Primate Fossil Record<\/em>, edited by Joseph Plavcan, Richard F. Kay, William Jungers, and Carel P. van Schaik, 261\u2013296. New York: Kluwer Academic\/Plenum Publishers.<\/p>\n<h2 class=\"import-Normal\">References<\/h2>\n<p class=\"import-Normal\">Agust\u00ed, J., A. Sanz de Siria, and M. Garc\u00e9s M. 2003. \u201cExplaining the End of the Hominoid Experiment in Europe.\u201d <em>Journal of Human Evolution<\/em> 45 (2): 145\u2013153.<\/p>\n<p class=\"import-Normal\">Alba, David M., Sergio Alm\u00e9cija, Daniel DeMiguel, Josep Fortuny, Miriam P\u00e9rez de los R\u00edos, Marta Pina, Josep M. Robles, and Salvador Moy\u00e0-Sol\u00e0. 2015. \u201cMiocene Small-Bodied Ape from Eurasia Sheds Light on Hominoid Evolution.\u201d <em>Science<\/em> 350 (6260): aab2625.<\/p>\n<p class=\"import-Normal\">Andrews, Peter, and Lawrence Martin. 1991. \u201cHominoid Dietary Evolution.\u201d <em>Philosophical Transactions of the Royal Society of London B: Biological Sciences<\/em> 334 (1270): 199\u2013209.<\/p>\n<p class=\"import-Normal\">Antoine, Pierre-Oliver, Laurent Marivaux, Darren A. Croft, Guillaume Billet, Morgan Ganer\u00f8d, Carlos Jaramillo, Thomas Martin, et al. 2012. \u201cMiddle Eocene Rodents from Peruvian Amazonia Reveal the Pattern and Timing of Caviomorph Origins and Biogeography.\u201d <em>Proceedings of the Royal Society B: Biological Sciences<\/em> 279 (1732): 1319\u20131326.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher. 1990. \u201cGliding Behaviour and Palaeoecology of the Alleged Primate Family Paromomyidae (Mammalia, Dermoptera).\u201d <em>Nature<\/em> 345 (6273): 340\u2013341.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher. 2002. \u201cBasal Anthropoids.\u201d In <em>The Primate Fossil Record, <\/em>edited by William C. Hartwig, 133\u2013150. Cambridge: Cambridge University Press.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher, and R. D. E. MacPhee. 1994. \u201cCranial Anatomy of <em>Shoshonius<\/em> and the Antiquity of Anthropoidea.\u201d In <em>Anthropoid Origins: The Fossil Evidence<\/em>, edited by John G. Fleagle and Richard F. Kay, 55\u201398. New York: Plenum Press.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher, Laurent Marivaux, Soe Thura Tun, Aung Naing Soe, Yaowalak Chaimanee, Wanna Htoon, Bernard Marandat, Htun Htun Aung, and Jean-Jacques Jaeger. 2007. \u201cNew Sivaladapid Primates from the Eocene Pondaung Formation of Myanmar and the Anthropoid Status of Amphipithecidae.\u201d <em>Bulletin of Carnegie Museum of Natural History<\/em> 39: 67\u201376.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher, Tao Qi, Mary R. Dawson, Banyue Wang, and Chuankuei Li. 1994. \u201cA Diverse New Primate Fauna from Middle Eocene Fissure-Fillings in Southeastern China.\u201d <em>Nature<\/em> 368 (6472): 604\u2013609.<\/p>\n<p class=\"import-Normal\">Beard, K. Christopher, Yongsheng Tong, Mary R. 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Teaford. 1991. \u201c<em>Proconsul<\/em> Did Not Have a Tail.\u201d <em>Journal of Human Evolution<\/em> 21 (3): 215\u2013220.<\/p>\n<p class=\"import-Normal\">Wheeler, Brandon C. 2010. \u201cCommunity Ecology of the Middle Miocene Primates of La Venta, Colombia: The Relationship between Ecological Diversity, Divergence Time, and Phylogenetic Richness.\u201d <em>Primates<\/em> 51 (2): 131\u2013138.<\/p>\n<p class=\"import-Normal\">Williams, Blythe A., and Richard F. Kay. 1995. \u201cThe Taxon Anthropoidea and the Crown Clade Concept.\u201d <em>Evolutionary Anthropology<\/em> 3 (6): 188\u2013190.<\/p>\n<p class=\"import-Normal\">Williams, Blythe A., Richard F. Kay, and E. Christopher Kirk. 2010a. \u201cNew Perspectives on Anthropoid Origins.\u201d <em>Proceedings of the National Academy<\/em> <em>of the United States of America<\/em> 107 (11): 4797\u20134804.<\/p>\n<p class=\"import-Normal\">Williams, Blythe A., Richard F. Kay, E. Christopher Kirk, and Callum F. Ross. 2010b. \u201c<em>Darwinius masillae<\/em> Is a European Middle Eocene Stem Strepsirrhine\u2014A Reply to Franzen et al.\u201d <em>Journal of Human Evolution<\/em> 59(5): 567\u2013573.<\/p>\n<p class=\"import-Normal\">Wilson Mantilla, G. P., S. G. B. Chester, W. A. Clemens, J. R. Moore, C. J. Sprain, B. T. Hovatter, W. S. Mitchell, W. W. Mans, R. Mundil, and P. R. Renne. 2021. \u201cEarliest Palaeocene Purgatoriids and the Initial Radiation of Stem Primates.\u201d <em>Royal Society Open Science<\/em> 8(2):210050. doi:10.1098\/rsos.210050.<\/p>\n<h2 class=\"import-Normal\">Acknowledgments<\/h2>\n<p class=\"import-Normal\">We are immensely grateful to the editors of this book, Drs. Beth Shook, Lara Braff, Katie Nelson, and Kelsie Aguilera, for their time and commitment to making this knowledge freely accessible to all, and for giving us the opportunity to participate in this important project.<\/p>\n<\/div>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_280_1683\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1683\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1684\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1684\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1686\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1686\"><div 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class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_2568\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_2568\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1698\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1698\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1699\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1699\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1700\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1700\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1702\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1702\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1704\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1704\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1705\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1705\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_800\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_800\"><div tabindex=\"-1\"><div class=\"__UNKNOWN__\">\n<p class=\"import-Normal\">Andrea J. Alveshere, Ph.D., Western Illinois University<\/p>\n<h6>Student contributors for this chapter: Corin Laberge, Hazel Moorcroft, Isabella Michel, Julian J. Pantoja Quiroz<\/h6>\n<p class=\"import-Normal\"><em>This chapter is a revision from \"<\/em><a class=\"rId7\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\"><em>Chapter 4: Forces of Evolution<\/em><\/a><em>\u201d by Andrea J. Alveshere. In <\/em><a class=\"rId8\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\"><em>Explorations: An Open Invitation to Biological Anthropology, first edition<\/em><\/a><em>, edited by Beth Shook, Katie Nelson, Kelsie Aguilera, and Lara Braff, which is licensed under <\/em><a class=\"rId9\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\"><em>CC BY-NC 4.0<\/em><\/a><em>. <\/em><\/p>\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<h2 class=\"textbox__title\"><span style=\"color: #000000\">Learning Objectives<\/span><\/h2>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li class=\"import-Normal\">Outline a 21st-century perspective of the Modern Synthesis.<\/li>\n<li class=\"import-Normal\">Define populations and population genetics as well as the methods used to study them.<\/li>\n<li class=\"import-Normal\">Identify the forces of evolution and become familiar with examples of each.<\/li>\n<li class=\"import-Normal\">Discuss the evolutionary significance of mutation, genetic drift, gene flow, and natural selection.<\/li>\n<li class=\"import-Normal\">Explain how allele frequencies can be used to study evolution as it happens.<\/li>\n<li class=\"import-Normal\">Contrast micro- and macroevolution.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>It\u2019s hard for us, with our typical human life spans of less than 100 years, to imagine all the way back, 3.8 billion years ago, to the <strong>origins of life<\/strong>. Scientists still study and debate how life came into being and whether it originated on Earth or in some other region of the universe (including some scientists who believe that studying evolution can reveal the complex processes that were set in motion by God or a higher power). What we do know is that a living single-celled organism was present on Earth during the early stages of our planet\u2019s existence. This organism had the potential to reproduce by making copies of itself, just like bacteria, many amoebae, and our own living cells today. In fact, with modern technologies, we can now trace genetic lineages, or <strong>phylogenies<\/strong>, and determine the relationships between all of today\u2019s living organisms\u2014eukaryotes (animals, plants, fungi, etc.), archaea, and bacteria\u2014on the branches of the <strong>phylogenetic tree of life<\/strong> (Figure 5.1).<\/p>\n<figure style=\"width: 675px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2023\/02\/image1-1.png\" alt=\"Branches lead off of a single celled universal ancestor to images of bacteria, archaea, and eukarya (represented by a mouse, mushroom, and fern, among others).\" width=\"675\" height=\"475\" \/><figcaption class=\"wp-caption-text\">Figure 5.1: Phylogenetic tree of life illustrating probable relationships between the single-celled Last Universal Common Ancestor (LUCA) and select examples of bacteria, archaea, and eukaryotes. Major evolutionary developments, including independent evolution of multicellularity, photosynthesis, and respiration, are indicated along the branches. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit: <a class=\"rId11\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Cladograma_dos_Dom%C3%ADnios_e_Reinos.png\">Cladograma dos Dominios e Reinos<\/a> by <a class=\"rId12\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:MarceloTeles\">MarceloTeles<\/a> has been modified (English labels replace Portuguese) and is under a <a class=\"rId13\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0 License<\/a>..<\/figcaption><\/figure>\n<p class=\"import-Normal\">Looking at the common sequences in modern genomes, we can even make educated guesses about the likely genetic sequence of the <strong>Last Universal Common Ancestor (LUCA)<\/strong> of all living things. Through a wondrous series of mechanisms and events over nearly four billion years, that ancient single-celled organism gave rise to the rich diversity of species that fill the lands, seas, and skies of our planet. This chapter explores the mechanisms by which that amazing transformation occurred and considers some of the crucial scientific experiments that shaped our current understanding of the evolutionary process.<\/p>\n<h2 class=\"import-Normal\">Population Genetics<\/h2>\n<h3 class=\"import-Normal\"><strong>Defining Populations and the Variations <\/strong><strong>w<\/strong><strong>ithin Them<\/strong><\/h3>\n<p class=\"import-Normal\">One of the major breakthroughs in understanding the mechanisms of evolutionary change came with the realization that evolution takes place at the level of populations, not within individuals. In the biological sciences, a <strong>p<\/strong><strong>opulation<\/strong> is defined as a group of individuals of the same <strong>species<\/strong> who are geographically near enough to one another that they can breed and produce new generations of individuals.<\/p>\n<p class=\"import-Normal\">For the purpose of studying evolution, we recognize populations by their even smaller units: genes. Remember, a\u00a0<strong>gene<\/strong> is the basic unit of information that encodes the proteins needed to grow and function as a living organism. Each gene can have multiple <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_280_738\">alleles<\/a><\/strong>, or variants\u2014each of which may produce a slightly different protein. Each individual, for genetic inheritance purposes, carries a collection of genes that can be passed down to future generations. For this reason, in population genetics, we think of populations as <strong>gene pools<\/strong>, which refers to the entire collection of genetic material in a breeding community that can be passed on from one generation to the next.<\/p>\n<p class=\"import-Normal\">For genes carried on our human chromosomes (our nuclear DNA), we inherit two copies of each, one from each parent. This means we may carry two of the same alleles (a <strong>homozygous genotype<\/strong>) or two different alleles (a <strong>heterozygous<\/strong> <strong>genotype<\/strong>) for each nuclear gene.<\/p>\n<h3 class=\"import-Normal\"><strong>Defining Evolution <\/strong><\/h3>\n<p class=\"import-Normal\">In order to understand evolution, it\u2019s crucial to remember that evolution is always studied at the population level. Also, if a population were to stay exactly the same from one generation to the next, it would not be evolving. So evolution requires both a population of breeding individuals and some kind of a genetic change occurring within it. Thus, the simple definition of <strong>evolution<\/strong> is a change in the allele frequencies in a population over time. What do we mean by allele frequencies? <strong>Allele frequencies<\/strong> refer to the ratio, or percentage, of one allele (one variant of a gene) compared to the other alleles for that gene within the study population (Figure 5.2). By contrast, <strong>genotype frequencies<\/strong> are the ratios or percentages of the different homozygous and heterozygous genotypes in the population. Because we carry two alleles per <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_280_736\">genotype<\/a><\/strong>, the total count of alleles in a population will usually be exactly double the total count of genotypes in the same population (with the exception being rare cases in which an individual carries a different number of chromosomes than the typical two; e.g., Down syndrome results when a child carries three copies of Chromosome 21).<\/p>\n<figure style=\"width: 652px\" class=\"wp-caption aligncenter\"><img class=\"\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image2.jpg\" alt=\"Genotypes are represented as combinations of alleles and allele frequencies.\" width=\"652\" height=\"883\" \/><figcaption class=\"wp-caption-text\">Figure 5.2: Population evolution can be measured by allele frequency changes. This diagram illustrates the differences between genotype frequencies and allele frequencies, as well as how they can be measured in a population of snapdragon flowers. The lower portion of the diagram also depicts how evolution is recognized as allele frequencies change in a population over time. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>.\u00a0Credit: Population evolution original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Katie Nelson and Beth Shook is a collective work under a <a class=\"rId15\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\">CC BY-NC 4.0 License<\/a>. [Includes <a class=\"rId16\" href=\"https:\/\/pixabay.com\/vectors\/snapdragon-flower-pink-lilac-plant-146850\/\">Snapdragon-flower-pink-lilac<\/a> by <a class=\"rId17\" href=\"https:\/\/pixabay.com\/users\/openclipart-vectors-30363\/\">OpenClipart-Vectors<\/a>, <a class=\"rId18\" href=\"https:\/\/creativecommons.org\/share-your-work\/public-domain\/cc0\/\">public domain (CC0)<\/a> under a <a class=\"rId19\" href=\"https:\/\/pixabay.com\/service\/terms\/\">Pixabay License<\/a>.]<\/figcaption><\/figure>\n<h2 class=\"import-Normal\">The Forces of Evolution<\/h2>\n<p class=\"import-Normal\">Today, we recognize that evolution takes place through a combination of mechanisms: mutation, genetic drift, gene flow, and natural selection. These mechanisms are called the \u201cforces of evolution\u201d; together they account for all the genotypic variation observed in the world today. Keep in mind that each of these forces was first defined and then tested\u2014and retested\u2014through the experimental work of the many scientists who contributed to the Modern Synthesis.<\/p>\n<h3 class=\"import-Normal\"><strong>Mutation<\/strong><\/h3>\n<p class=\"import-Normal\">The first force of evolution we will discuss is mutation, and for good reason: mutation is the original source of all the genetic variation found in every living thing. Imagine all the way back in time to the very first single-celled organism, floating in Earth\u2019s primordial sea. Based on what we observe in simple, single-celled organisms today, that organism probably spent its lifetime absorbing nutrients and dividing to produce cloned copies of itself. While the numbers of individuals in that population would have grown (as long as the environment was favorable), nothing would have changed in that perfectly cloned population. There would not have been variety among the individuals. It was only through a copying error\u2014the introduction of a <strong>mutation<\/strong>, or change, into the genetic code\u2014that new alleles were introduced into the population.<br style=\"clear: both\" \/><br style=\"clear: both\" \/>After many generations have passed in our primordial population, mutations have created distinct chromosomes. The cells are now amoeba-like, larger than many of their tiny bacterial neighbors, who have long since become their favorite source of nutrients. Without mutation to create this diversity, all living things would still be identical to LUCA, our universal ancestor (Figure 5.3).<\/p>\n<figure style=\"width: 663px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image3-2.png\" alt=\"Universal Ancestor linked to the Eukarya branch.\" width=\"663\" height=\"338\" \/><figcaption class=\"wp-caption-text\">Figure 5.3: Key mutational differences between Last Universal Common Ancestor and an amoeba-like primordial cell. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit<strong>: <\/strong>Key differences between LUCA and a primordial cell original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId21\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId22\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Cladograma_dos_Dom%C3%ADnios_e_Reinos.png\">Cladograma dos Dominios e Reinos<\/a> by <a class=\"rId23\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:MarceloTeles\">MarceloTeles<\/a> (cropped, labels and color changed), <a class=\"rId24\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a><a class=\"rId25\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">; <\/a><a class=\"rId26\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId27\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId28\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (cropped and color changed), <a class=\"rId29\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>.]<\/figcaption><\/figure>\n<p class=\"import-Normal\">When we think of genetic mutation, we often first think of <strong>deleterious mutations<\/strong>\u2014the ones associated with negative effects such as the beginnings of cancers or heritable disorders. The fact is, though, that every genetic adaptation that has helped our ancestors survive since the dawn of life is directly due to <strong>beneficial mutations<\/strong>\u2014changes in the DNA that provided some sort of advantage to a given population at a particular moment in time. For example, a beneficial mutation allowed chihuahuas and other tropical-adapted dog breeds to have much thinner fur coats than their cold-adapted cousins the northern wolves, malamutes, and huskies.<\/p>\n<figure style=\"width: 320px\" class=\"wp-caption alignleft\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image4-1-1.png\" alt=\"UV radiation damages nucleotides in DNA.\" width=\"320\" height=\"248\" \/><figcaption class=\"wp-caption-text\">Figure 5.4: A crosslinking mutation in which a UV photon induces a bond between two thymine bases. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit<strong>: <\/strong><a class=\"rId31\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">UV-induced Thymine dimer mutation (Figure 4.6)<\/a> original to <a class=\"rId32\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId33\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Every one of us has genetic mutations. Yes, even you. The DNA in some of your cells today differs from the original DNA that you inherited when you were a tiny, fertilized egg. Mutations occur all the time in the cells of our skin and other organs, due to chemical changes in the nucleotides. Exposure to the UV radiation in sunlight is one common cause of skin mutations. Interaction with UV light causes <strong>UV crosslinking<\/strong>, in which adjacent thymine bases bind with one another (Figure 5.4). Many of these mutations are detected and corrected by <strong>DNA repair mechanisms<\/strong>, enzymes that patrol and repair DNA in living cells, while other mutations may cause a new freckle or mole or, perhaps, an unusual hair to grow. For people with the <strong>autosomal recessive<\/strong> disease <strong>xeroderma pigmentosum<\/strong>, these repair mechanisms do not function correctly, resulting in a host of problems especially related to sun exposure, including severe sunburns, dry skin, heavy freckling, and other pigment changes.<\/p>\n<p class=\"import-Normal\">Most of our mutations exist in <strong>somatic<\/strong> cells, which are the cells of our organs and other body tissues. Those will not be passed onto future generations and so will not affect the population over time. Only mutations that occur in the <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_280_686\">gametes<\/a><\/strong>, the reproductive cells (i.e., the sperm or egg cells), will be passed onto future generations. When a new mutation pops up at random in a family lineage, it is known as a <strong>spontaneous mutation<\/strong>. If the individual born with this spontaneous mutation passes it on to his offspring, those offspring receive an <strong>inherited mutation<\/strong>. Geneticists have identified many classes of mutations and the causes and effects of many of these.<\/p>\n<h4 class=\"import-Normal\"><em>Point Mutations<\/em><\/h4>\n<p class=\"import-Normal\">A <strong>point mutation<\/strong> is a single-letter (single-nucleotide) change in the genetic code resulting in the substitution of one nucleic acid base for a different one. As you learned in Chapter 3, the DNA code in each gene is translated through three-letter \u201cwords\u201d known as <strong>codons<\/strong>. So depending on how the point mutation changes the \u201cword,\u201d the effect it will have on the protein may be major or minor or may make no difference at all.<\/p>\n<p class=\"import-Normal\">If a mutation does not change the resulting protein, then it is called a <strong>synonymous mutation<\/strong>. Synonymous mutations do involve a letter (nucleic acid) change, but that change results in a codon that codes for the same \u201cinstruction\u201d (the same amino acid or stop code) as the original codon. Mutations that do cause a change in the protein are known as <strong>nonsynonymous mutations<\/strong>. Nonsynonymous mutations may change the resulting protein\u2019s amino acid sequence by altering the DNA sequence that encodes the mRNA or by changing how the mRNA is spliced prior to translation (refer to Chapter 3 for more details).<\/p>\n<h4 class=\"import-Normal\"><em>Insertions and Deletions<\/em><\/h4>\n<p class=\"import-Normal\">In addition to point mutations, another class of mutations are <strong>insertions<\/strong> and <strong>deletions<\/strong>, or <strong>indels<\/strong>, for short. As the name suggests, these involve the addition (insertion) or removal (deletion) of one or more coding sequence letters (nucleic acids). These typically first occur as an error in DNA replication, wherein one or more nucleotides are either duplicated or skipped in error. Entire codons or sets of codons may also be removed or added if the indel is a multiple of three nucleotides.<\/p>\n<p class=\"import-Normal\"><strong>Frameshift<\/strong> <strong>mutations<\/strong> are types of indels that involve the insertion or deletion of any number of nucleotides that is not a multiple of three (e.g., adding one or two extra letters to the code). Because these indels are not consistent with the codon numbering, they \u201cshift the reading frame,\u201d causing all the codons beyond the mutation to be misread. Like point mutations, small indels can also disrupt splice sites.<\/p>\n<p class=\"import-Normal\"><strong>Transposable elements<\/strong>, or <strong>transposons<\/strong>, are fragments of DNA that can \u201cjump\u201d around in the genome. There are two types of transposons: <strong>retrotransposons<\/strong> are transcribed from DNA into RNA and then \u201creverse transcribed,\u201d to insert the copied sequence into a new location in the DNA, and<strong> DNA transposons<\/strong>, which do not involve RNA. DNA transposons are clipped out of the DNA sequence itself and inserted elsewhere in the genome. Because transposable elements insert themselves into existing DNA sequences, they are frequent gene disruptors. At certain times, and in certain species, it appears that transposons became very active, likely accelerating the mutation rate (and thus, the genetic variation) in those populations during the active periods.<\/p>\n<h4 class=\"import-Normal\"><em>Chromosomal Alterations <\/em><\/h4>\n<p class=\"import-Normal\">The final major category of genetic mutations are changes at the chromosome level: crossover events, nondisjunction events, and translocations. <strong>Crossover events<\/strong>  occur when DNA is swapped between homologous chromosomes while they are paired up during meiosis I. Crossovers are thought to be so common that some DNA swapping may happen every time chromosomes go through meiosis I. Crossovers don\u2019t necessarily introduce new alleles into a population, but they do make it possible for new combinations of alleles to exist on a single chromosome that can be passed to future generations. This also enables new combinations of alleles to be found within siblings who share the same parents. Also, if the fragments that cross over don\u2019t break at exactly the same point, they can cause genes to be deleted from one of the homologous chromosomes and duplicated on the other.<\/p>\n<p class=\"import-Normal\"><strong>Nondisjunction events<\/strong> occur when the homologous chromosomes (in meiosis I) or sister chromatids (in meiosis II and mitosis) fail to separate after pairing. The result is that both chromosomes or chromatids end up in the same daughter cell, leaving the other daughter cell without any copy of that chromosome (Figure 5.5). Most nondisjunctions at the gamete level are fatal to the embryo. The most widely known exception is Trisomy 21, or Down syndrome, which results when an embryo inherits three copies of Chromosome 21: two from one parent (due to a nondisjunction event) and one from the other (Figure 5.6). <strong>Trisomies <\/strong>(triple chromosome conditions) of Chromosomes 18 (Edwards syndrome) and 13 (Patau syndrome) are also known to result in live births, but the children usually have severe complications and rarely survive beyond the first year of life.<\/p>\n<figure style=\"width: 601px\" class=\"wp-caption aligncenter\"><img class=\"\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image5.jpg\" alt=\"Egg cell undergoes normal meiosis and nondisjunction in meisosis 1.\" width=\"601\" height=\"391\" \/><figcaption class=\"wp-caption-text\">Figure 5.5: Illustration of an egg cell (oocyte) undergoing normal meiosis 1, resulting in a diploid daughter cell, compared to an egg cell undergoing nondisjunction during meiosis 1, resulting in a trisomy in the daughter cell. Credit: <a class=\"rId35\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Trisomy_due_to_nondisjunction_in_maternal_meiosis_1.png\">Trisomy due to nondisjunction in maternal meiosis 1<\/a> by Wpeissner has been modified (labels deleted by Katie Nelson) and is under a <a class=\"rId36\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>.<\/figcaption><\/figure>\n<figure style=\"width: 316px\" class=\"wp-caption alignright\"><img class=\"\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image6-1.jpg\" alt=\"A young woman in a blue polo shirt smiles at the camera.\" width=\"316\" height=\"364\" \/><figcaption class=\"wp-caption-text\">Figure 5.6: Amy Bockerstette, a competitive golfer and disabilities advocate, also has Down Syndrome. Credit: <a class=\"rId38\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amy_Bockerstette_Headshot.jpg\">Amy Bockerstette Headshot<\/a> by Bucksgrandson is under a <a class=\"rId39\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\">CC BY-SA 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Sex chromosome trisomies (XXX, XXY, XYY) and X chromosome <strong>monosomies<\/strong> (inheritance of an X chromosome from one parent and no sex chromosome from the other) are also survivable and fairly common. The symptoms vary but often include atypical sexual characteristics, either at birth or at puberty, and often result in sterility. The X chromosome carries unique genes that are required for survival; therefore, Y chromosome monosomies are incompatible with life.<\/p>\n<p class=\"import-Normal\"><strong>Chromosomal translocations<\/strong> involve transfers of DNA between nonhomologous chromosomes. This may involve swapping large portions of two or more chromosomes. The exchanges of DNA may be balanced or unbalanced. In <strong>balanced translocations<\/strong>, the genes are swapped, but no genetic information is lost. In <strong>unbalanced translocations<\/strong>, there is an unequal exchange of genetic material, resulting in duplication or loss of genes. Translocations result in new chromosomal structures called <strong>derivative chromosomes<\/strong>, because they are derived or created from two different chromosomes<em>. <\/em>Translocations are often found to be linked to cancers and can also cause infertility. Even if the translocations are balanced in the parent, the embryo often won\u2019t survive unless the baby inherits both of that parent\u2019s derivative chromosomes (to maintain the balance).<\/p>\n<h3 class=\"import-Normal\"><strong>Genetic Drift<\/strong><\/h3>\n<p class=\"import-Normal\">The second force of evolution is commonly known as genetic drift. This is an unfortunate misnomer, as this force actually involves the drifting of alleles, not genes. <strong>Genetic <\/strong><strong>d<\/strong><strong>rift<\/strong> refers to <em>random<\/em> changes (\u201cdrift\u201d) in allele frequencies from one generation to the next. The genes are remaining constant within the population; it is only the alleles of the genes that are changing in frequency. The random nature of genetic drift is a crucial point to understand: it specifically occurs when none of the variant alleles confer an advantage.<\/p>\n<figure style=\"width: 368px\" class=\"wp-caption alignright\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image7-2.png\" alt=\"A smooth cell has a gently curving exterior surface, and a ruffled cell has undulating surface.\" width=\"368\" height=\"215\" \/><figcaption class=\"wp-caption-text\">Figure 5.7: Smooth and ruffled amoeba-like cells. Credit: Smooth and ruffled amoeba-like cells original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId41\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId42\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId43\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId44\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (modified), <a class=\"rId45\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>.]<\/figcaption><\/figure>\n<p class=\"import-Normal\">Let\u2019s imagine far back in time, again, to that ancient population of amoeba-like cells, subsisting and occasionally dividing, in the primordial sea. A mutation occurs in one of the cells that changes the texture of the cell membrane from a relatively smooth surface to a highly ruffled one (Figure 5.7). This has absolutely no effect on the cell\u2019s quality of life or ability to reproduce. In fact, eyes haven\u2019t evolved yet, so no one in the world at the time would even notice the difference. The cells in the population continue to divide, and the offspring of the ruffled cell inherit the ruffled membrane. The frequency (percentage) of the ruffled allele in the population, from one generation to the next, will depend entirely on how many offspring that first ruffled cell ends up having, and the random events that might make the ruffled alleles more common or more rare (such as population bottlenecks and founder effects, which are discussed below).<\/p>\n<h4 class=\"import-Normal\"><em>Sexual Reproduction and Random Inheritance<\/em><\/h4>\n<p class=\"import-Normal\">Tracking alleles gets a bit more complicated in our primordial cells when, after a number of generations, a series of mutations have created populations that reproduce sexually. These cells now must go through an extra round of cell division (meiosis) to create haploid gametes. The combination of two gametes is now required to produce each new diploid offspring.<\/p>\n<figure style=\"width: 262px\" class=\"wp-caption alignleft\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image8-1.png\" alt=\"A Punnett square with ruffled and smooth cells.\" width=\"262\" height=\"262\" \/><figcaption class=\"wp-caption-text\">Figure 5.8: A Punnett square demonstrating the sexual inheritance pattern of ruffled (dominant) and smooth amoeba-like primordial cells. Credit: Punnett square of primordial cells original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId47\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId48\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId49\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId50\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (modified), <a class=\"rId51\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>; <a class=\"rId52\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Punnett_hetero_x_hetero.svg\">Punnett Hetero x Hetero<\/a> by <a class=\"rId53\" href=\"https:\/\/commons.wikimedia.org\/w\/index.php?title=User:Purpy_Pupple&amp;redirect=no\">Purpy Pupple<\/a> (modified), <a class=\"rId54\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/deed.en\">CC BY-SA 3.0<\/a>].<\/figcaption><\/figure>\n<p class=\"import-Normal\">In the earlier population, which reproduced via <strong>asexual reproduction<\/strong>, a cell either carried the smooth allele or the ruffled allele. With <strong>sexual reproduction<\/strong>, a cell inherits one allele from each parent, so there are homozygous cells that contain two smooth alleles, homozygous cells that contain two ruffled alleles, and heterozygous cells that contain one of each allele (Figure 5.8). If the new, ruffled allele happens to be dominant (and we\u2019ll imagine that it is), the heterozygotes will have ruffled cell <strong>phenotypes<\/strong> but also will have a 50\/50 chance of passing on a smooth allele to each offspring. As long as neither phenotype (ruffled nor smooth) provides any advantage over the other, the variation in the population from one generation to the next will remain completely random.<\/p>\n<p class=\"import-Normal\">In sexually reproducing populations (including humans and many other animals and plants in the world today), that 50\/50 chance of inheriting one or the other allele from each parent plays a major role in the random nature of genetic drift.<\/p>\n<h4 class=\"import-Normal\"><em>Population Bottlenecks <\/em><\/h4>\n<p class=\"import-Normal\">A <strong>population bottleneck<\/strong> occurs when the number of individuals in a population drops dramatically due to some random event. The most obvious, familiar examples are natural disasters. Tsunamis and hurricanes devastating island and coastal populations and forest fires and river floods wiping out populations in other areas are all too familiar. When a large portion of a population is randomly wiped out, the allele frequencies (i.e., the percentages of each allele) in the small population of survivors are often much different from the frequencies in the predisaster, or \u201cparent,\u201d population.<\/p>\n<p class=\"import-Normal\">If such an event happened to our primordial ocean cell population\u2014perhaps a volcanic fissure erupted in the ocean floor and only the cells that happened to be farthest from the spewing lava and boiling water survived\u2014we might end up, by random chance, with a surviving population that had mostly ruffled alleles, in contrast to the parent population, which had only a small percentage of ruffles (Figure 5.9).<\/p>\n<figure style=\"width: 665px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image9-2.png\" alt=\"Ruffled and smooth cells experience population bottleneck when a lava flow divides the populations.\" width=\"665\" height=\"332\" \/><figcaption class=\"wp-caption-text\">Figure 5.9: Illustration of a population of amoeba-like cells shifting from primarily smooth phenotypes (at left) to mostly ruffled phenotypes due to eruption of a volcanic fissure (at right) that exterminated the nearest cells. Credit: Population of amoeba-like cells and volcanic fissure original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId56\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId57\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId58\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId59\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (modified), <a class=\"rId60\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>.]<\/figcaption><\/figure>\n<p class=\"import-Normal\">One of the most famous examples of a population bottleneck is the prehistoric disaster that led to the extinction of dinosaurs, the <strong>Cretaceous\u2013Paleogene <\/strong><strong>extinction<\/strong> event (often abbreviated K\u2013Pg; previously K-T). This occurred approximately 66 million years ago. Dinosaurs and all their neighbors were going about their ordinary routines when a massive asteroid zoomed in from space and crashed into what is now the Gulf of Mexico, creating an impact so enormous that populations within hundreds of miles of the crash site were likely immediately wiped out. The skies filled with dust and debris, causing temperatures to plummet worldwide. It\u2019s estimated that 75% of the world\u2019s species went extinct as a result of the impact and the deep freeze that followed (Jablonski and Chaloner 1994).<\/p>\n<figure style=\"width: 399px\" class=\"wp-caption alignleft\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image10-2.png\" alt=\" A rat-like creature sits atop a dinosaur, raising a fist in a victorious gesture.\" width=\"399\" height=\"323\" \/><figcaption class=\"wp-caption-text\">Figure 5.10: The Cretaceous\u2013Paleogene extinction event, which led to the fall of the dinosaurs and rise of the mammals. Credit: <a class=\"rId62\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">The<\/a> <a class=\"rId64\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Cretaceous\u2013Paleogene extinction event (Figure 4.12)<\/a> original to <a class=\"rId65\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId66\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">The populations that emerged from the K-Pg extinction were markedly different from their pre-disaster communities. Surviving mammal populations expanded and diversified, and other new creatures appeared. The ecosystems of Earth were filled with new organisms and have never been the same (Figure 5.10).<\/p>\n<p class=\"import-Normal\">Much more recently in geological time, during the colonial period, many human populations experienced bottlenecks as a result of the fact that imperial powers were inclined to slaughter communities who were reluctant to give up their lands and resources. This effect was especially profound in the Americas, where Indigenous populations faced the compounded effects of brutal warfare, exposure to new bacteria and viruses (against which they had no immunity), and ultimately segregation on resource-starved reservations. The populations in Europe, Asia, and Africa had experienced regular gene flow during the 10,000-year period in which most kinds of livestock were being domesticated, giving them many generations of experience building up immunity against zoonotic diseases (those that can pass from animals to humans). In contrast, the residents of the Americas had been almost completely isolated during those millennia, so all these diseases swept through the Americas in rapid succession, creating a major loss of genetic diversity in the Indigenous American population. It is estimated that between 50% and 95% of the Indigenous American populations died during the first decades after European contact, around 500 years ago (Livi-Bacci 2006).<\/p>\n<p class=\"import-Normal\">An urgent health challenge facing humans today involves human-induced population bottlenecks that produce antibiotic-resistant bacteria. <strong>Antibiotics<\/strong> are medicines prescribed to treat bacterial infections. The typical prescription includes enough medicine for ten days. People often feel better much sooner than ten days and sometimes decide to quit taking the medicine ahead of schedule. This is often a big mistake. The antibiotics have quickly killed off a large percentage of the bacteria\u2014enough to reduce the symptoms and make you feel much better. However, this has created a bacterial population bottleneck. There are usually a small number of bacteria that survive those early days. If you take the medicine as prescribed for the full ten days, it\u2019s quite likely that there will be no bacterial survivors. If you quit early, though, the survivors\u2014who were the members of the original population who were most resistant to the antibiotic\u2014will begin to reproduce again. Soon the infection will be back, possibly worse than before, and now all of the bacteria are resistant to the antibiotic that you had been prescribed.<\/p>\n<p class=\"import-Normal\">Other activities that have contributed to the rise of antibiotic-resistant bacteria include the use of antibacterial cleaning products and the inappropriate use of antibiotics as a preventative measure in livestock or to treat infections that are viral instead of bacterial (viruses do not respond to antibiotics). In 2017, the World Health Organization published a list of twelve antibiotic-resistant pathogens that are considered top priority targets for the development of new antibiotics (World Health Organization 2017).<\/p>\n<div class=\"textbox shaded\" style=\"background: var(--lightblue)\">\n<h2>Dig Deeper: The North American Elephant Seal: Thriving Bottleneck Populations That Still Face Genetic Defects<\/h2>\n<p>In 1892, the Northern Elephant Seal underwent a severe population bottleneck caused by commercial hunting, reducing the species to an estimated 20 individuals at the time. This drastic decline led to a substantial loss of genetic diversity\u2013a common consequence of extreme population bottlenecks (Hoelzel et al., 2024 &amp; Weber et al., 2000). While the population has since recovered to over 200,000 individuals, its genetic variability remains significantly low. Analyses of genetic markers, including allozymes, mitochondrial DNA, and microsatellites, consistently reflect this reduced diversity (Hoelzel et al., 2024). Comparative studies further underscore this loss by highlighting the higher genetic variation observed in the Southern Elephant Seal, which did not experience similar population constraints (2024).<\/p>\n<figure style=\"width: 386px\" class=\"wp-caption alignleft\"><img src=\"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/4\/48\/Elephant_seals_at_Ano_Nuevo_%2891577%29.jpg\/250px-Elephant_seals_at_Ano_Nuevo_%2891577%29.jpg\" alt=\"File:Elephant seals at Ano Nuevo (91577).jpg\" width=\"386\" height=\"295\" \/><figcaption class=\"wp-caption-text\"><span style=\"background-color: #ffff00\">Figure 5.24<\/span> A male northern elephant seal (Mirounga angustirostris) with two pups at Ano Nuevo State Park. Credit: Elephant seals at Ano Nuevo by Rhododendrites is under <a href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\" target=\"_blank\" rel=\"noopener\">Creative Commons Attribution-Share Alike 4.0<\/a>.<\/figcaption><\/figure>\n<p>In a 2024 study for Nature, Ecology, and Evolution, Hoelzel and colleagues sequenced 260 modern and 8 historical genomes of the northern elephant seal. This comparison revealed a decrease in average heterozygosity from 0.00142 before the bottleneck to 0.000176 in the contemporary population, confirming the decline in genetic variation (2024). Hoelzel\u2019s mitogenome tree further illustrates this loss, revealing only two significant lineages remaining post-bottleneck, with limited diversity within each. Among the issues of diversity, the population has shown an increased number of loss-of-function (LOF) alleles, suggesting that increased inbreeding has amplified the frequency of these detrimental alleles; this reduced genetic diversity negatively affects both male and female reproductive fitness. Females who practiced repetitive inbreeding had higher LOF alleles and subsequently weaned fewer pups per year over their lifetime, while male reproductive success was linked to specific LOF loci associated with sperm production (2024). Hoelzel uses the example of \u201cAlpha-Male M12\u201d\u2013known for low paternity success despite frequent copulations\u2013which was homozygous for non-functional versions of four out of five LOF loci related to sperm function (2024, p. 688). The species' mating system, characterized by extreme polygyny, further exacerbates the loss of genetic variation even with countless copulatory partners<\/p>\n<p>Prior research published in Current Biology presents an empirical genetic assessment of this population bottleneck, highlighting its long-term genetic consequences, particularly the loss of mitochondrial diversity (Weber et al., 2000). In this research, Weber and colleagues note that random lineage sampling during the bottleneck led to the persistence of specific genetic variants by chance rather than through natural selection (2000). This research emphasizes that the loss of diversity poses potential future genetic vulnerabilities for the seals, and that further studies are crucial for understanding the full scope of these impacts on the seals' overall fitness (2000). In 2024, the work led by Hoelzen and company provided the missing data that the previous study had left unanswered. Their previously explored findings indicate that, although the seals have recovered in numbers, their genetic resilience remains compromised, leaving the population more vulnerable to future environmental pressures, such as climate change or resource shortages (Hoelzel et al., 2024). Ultimately, while the population's size remains stable, the genetic consequences of the bottleneck indicate that past stochastic events continue to influence the seals' long-term fitness and adaptability.<\/p>\n<p>This research indicates that the historical bottleneck continues to affect the seals' health and fitness, despite the population's recovery. Limited genetic diversity and the persistence of harmful alleles due to inbreeding have continued to handicap the species' ability to thrive in environmental challenges such as climate change and resource fluctuations (2024). This emphasizes the importance of incorporating genetic factors into conservation strategies, as populations that have rebounded may still harbour long-term genetic weaknesses. Moreover, the elephant seal\u2019s history serves as a powerful example of how human actions \u2014such as overhunting \u2014 can have long-lasting impacts on biodiversity, reinforcing the importance of understanding human-environment interactions in ecological and conservation contexts.<\/p>\n<\/div>\n<h4 class=\"import-Normal\"><em>Founder Effects<\/em><\/h4>\n<p class=\"import-Normal\"><strong>Founder effects<\/strong> occur when members of a population leave the main or \u201cparent\u201d group and form a new population that no longer interbreeds with the other members of the original group. Similar to survivors of a population bottleneck, the newly founded population often has allele frequencies that are different from the original group. Alleles that may have been relatively rare in the parent population can end up being very common due to the founder effect. Likewise, recessive traits that were seldom seen in the parent population may be seen frequently in the descendants of the offshoot population.<\/p>\n<p class=\"import-Normal\">One striking example of the founder effect was first noted in the Dominican Republic in the 1970s. During a several-year period, eighteen children who had been born with female genitalia and raised as girls suddenly grew penises at puberty. This culture tended to value sons over daughters, so these transitions were generally celebrated. They labeled the condition <em><strong>guevedoces<\/strong><\/em>, which translates to \u201cpenis at twelve,\u201d due to the average age at which this occurred. Scientists were fascinated by the phenomenon.<\/p>\n<p class=\"import-Normal\">Genetic and hormonal studies revealed that the condition, scientifically termed <strong>5-alpha reductase deficiency,<\/strong> is an autosomal recessive syndrome that manifests when a child having both X and Y sex chromosomes inherits two nonfunctional (mutated) copies of the <em>SRD5A2 <\/em>gene (Imperato-McGinley and Zhu 2002). These children develop testes internally, but the 5-alpha reductase 2 steroid, which is necessary for development of male genitals in babies, is not produced. In absence of this male hormone, the baby develops female-looking genitalia (in humans, \u201cfemale\u201d is the default infant body form, if the full set of the necessary male hormones are not produced). At puberty, however, a different set of male hormones are produced by other fully functional genes. These hormones complete the male genital development that did not happen in infancy. This condition became quite common in the Dominican Republic during the 1970s due to founder effect\u2014that is, the mutated <em>SRD5A2<\/em>\u00a0gene happened to be much more common among the Dominican Republic\u2019s founding population than in the parent populations. (The Dominican population derives from a mixture of Indigenous Americans [Taino] peoples, West Africans, and Western Europeans.) Five-alpha reductase syndrome has since been observed in other small, isolated populations around the world.<\/p>\n<p class=\"import-Normal\">Founder effect is closely linked to the concept of inbreeding, which in population genetics does not necessarily mean breeding with immediate family relatives. Instead, <strong>inbreeding<\/strong>  refers to the selection of mates exclusively from within a small, closed population\u2014that is, from a group with limited allelic variability. This can be observed in small, physically isolated populations but also can happen when cultural practices limit mates to a small group. As with the founder effect, inbreeding increases the risk of inheriting two copies of any nonfunctional (mutant) alleles.<\/p>\n<p class=\"import-Normal\">The Amish in the United States are a population that, due to their unique history and cultural practices, emerged from a small founding population and have tended to select mates from within their groups. The <strong>Old Order Amish<\/strong> population of Lancaster County, Pennsylvania, has approximately 50,000 current members, all of whom can trace their ancestry back to a group of approximately 80 individuals. This small founding population immigrated to the United States from Switzerland in the mid-1700s to escape religious persecution. Since the Amish keep to themselves and almost exclusively select mates from within their own communities, they have more recessive traits compared to their parent population.<\/p>\n<figure style=\"width: 441px\" class=\"wp-caption alignright\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image11-1.jpg\" alt=\"One individual\u2019s hands with six fingers.\" width=\"441\" height=\"331\" \/><figcaption class=\"wp-caption-text\">Figure 5.11: A person displaying polydactyly. Credit: <a class=\"rId68\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:6_Finger.JPG\">6 Finger<\/a> by Wilhelmy is under a <a class=\"rId69\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/legalcode\">CC BY-SA 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">One of the genetic conditions that has been observed much more frequently in the Lancaster County Amish population is <strong>Ellis-van Creveld syndrome<\/strong>, which is an autosomal recessive disorder characterized by short stature (dwarfism), polydactyly (the development of more than five digits [fingers or toes] on the hands or feet], abnormal tooth development, and heart defects (Figure 5.11). Among the general world population, Ellis-van Creveld syndrome is estimated to affect approximately 1 in 60,000 individuals; among the Old Order Amish of Lancaster County, the rate is estimated to be as high as 1 in every 200 births (D\u2019Asdia et al. 2013).<\/p>\n<p class=\"import-Normal\">One important insight that has come from the study of founder effects is that a limited gene pool carries a much higher risk for genetic diseases. Genetic diversity in a population greatly reduces these risks.<\/p>\n<h3 class=\"import-Normal\"><strong>Gene Flow<\/strong><\/h3>\n<p class=\"import-Normal\">The third force of evolution is traditionally called gene flow. As with genetic drift, this is a misnomer, because it refers to flowing alleles, not genes. (All members of the same species share the same genes; it is the alleles of those genes that may vary.) <strong>Gene <\/strong><strong>f<\/strong><strong>low<\/strong>  refers to the movement of alleles from one population to another. In most cases, gene flow can be considered synonymous with migration.<\/p>\n<p class=\"import-Normal\">Returning again to the example of our primordial cell population, let\u2019s imagine that, after the volcanic fissure opened up in the ocean floor, wiping out the majority of the parent population, two surviving populations developed in the waters on opposite sides of the fissure. Ultimately, the lava from the fissure cooled into a large island that continued to provide a physical barrier between the populations (Figure 5.12).<\/p>\n<figure style=\"width: 685px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image12-2.png\" alt=\"An illustration of gene flow.\" width=\"685\" height=\"342\" \/><figcaption class=\"wp-caption-text\">Figure 5.12: Smooth and predominantly ruffled amoeba-like populations separated by a volcanic eruption (at left) and an island (at right) with unidirectional gene flow moving from east to west with ocean currents. Credit: Population of amoeba-like cells separated by volcanic eruption original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId74\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId75\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId76\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId77\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (modified), <a class=\"rId78\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>.]<\/figcaption><\/figure>\n<p class=\"import-Normal\">In the initial generations after the eruption, due to founder effect, isolation, and random inheritance (genetic drift), the population to the west of the islands contained a vast majority of the ruffled membrane alleles while the eastern population carried only the smooth alleles. Ocean currents in the area typically flowed from east to west, sometimes carrying cells (facilitating gene flow) from the eastern (smooth) population to the western (ruffled) population. Due to the ocean currents, it was almost impossible for any cells from the western population to be carried eastward. Thus, for inheritance purposes, the eastern (smooth) population remained isolated. In this case, the gene flow is unidirectional (going only in one direction) and unbalanced (only one population is receiving the new alleles).<\/p>\n<p class=\"import-Normal\">Among humans, gene flow is often described as <strong>admixture<\/strong>. In forensic cases, anthropologists and geneticists are often asked to estimate the ancestry of unidentified human remains to help determine whether they match any missing persons\u2019 reports. This is one of the most complicated tasks in these professions because, while \u201crace\u201d or \u201cancestry\u201d involves simple checkboxes on a missing person\u2019s form, among humans today there are no truly distinct genetic populations. All modern humans are members of the same fully breeding compatible species, and all human communities have experienced multiple episodes of gene flow (admixture), leading all humans today to be so genetically similar that we are all members of the same (and only surviving) human subspecies: <em>Homo sapiens sapiens.<\/em><\/p>\n<p class=\"import-Normal\">Gene flow between otherwise isolated nonhuman populations is often termed <strong>hybridization..<\/strong> One example of this involves the hybridization and spread of <strong>Scutellata<\/strong><strong> honey bees<\/strong> (a.k.a. \u201ckiller bees\u201d) in the Americas. All honey bees worldwide are classified as <em>Apis mellifera.<\/em> Due to distinct adaptations to various environments around the world, there are 28 different subspecies of <em>Apis mellifera<\/em>.<\/p>\n<p class=\"import-Normal\">During the 1950s, a Brazilian biologist named Warwick E. Kerr experimented with hybridizing African and European subspecies of honey bees to try to develop a strain that was better suited to tropical environments than the European honey bees that had long been kept by North American beekeepers. Dr. Kerr was careful to contain the reproductive queens and drones from the African subspecies, but in 1957, a visiting beekeeper accidentally released 26 queen bees of the Scutellata subspecies (<em>Apis mellifera scutellata<\/em>) from southern Africa into the Brazilian countryside. The Scutellata bees quickly interbred with local European honey bee populations. The hybridized bees exhibited a much more aggressively defensive behavior, fatally or near-fatally attacking many humans and livestock that ventured too close to their hives. The hybridized bees spread throughout South America and reached Mexico and California by 1985. By 1990, permanent colonies had been established in Texas, and by 1997, 90% of trapped bee swarms around Tucson, Arizona, were found to be Scutellata hybrids (Sanford 2006).<\/p>\n<p class=\"import-Normal\">Another example involves the introduction of the <strong>Harlequin ladybeetle<\/strong>, <em>Harmonia axyridis<\/em>, native to East Asia, to other parts of the world as a \u201cnatural\u201d form of pest control. Harlequin ladybeetles are natural predators of some of the aphids and other crop-pest insects. First introduced to North America in 1916, the \u201cbiocontrol\u201d strains of Harlequin ladybeetles were considered to be quite successful in reducing crop pests and saving farmers substantial amounts of money. After many decades of successful use in North America, biocontrol strains of Harlequin ladybeetles were also developed in Europe and South America in the 1980s.<\/p>\n<p class=\"import-Normal\">Over the seven decades of biocontrol use, the Harlequin ladybeetle had never shown any potential for development of wild colonies outside of its native habitat in China and Japan. New generations of beetles always had to be reared in the lab. That all changed in 1988, when a wild colony took root near New Orleans, Louisiana. Either through admixture with a native ladybeetle strain, or due to a spontaneous mutation, a new allele was clearly introduced into this population that suddenly enabled them to survive and reproduce in a wide range of environments. This population spread rapidly across the Americas and had reached Africa by 2004.<\/p>\n<p class=\"import-Normal\">In Europe, the invasive, North American strain of Harlequin ladybeetle admixed with the European strain (Figure 5.13), causing a population explosion (Lombaert et al. 2010). Even strains specifically developed to be flightless (to curtail the spreading) produced flighted offspring after admixture with members of the North American population (Facon et al. 2011). The fast-spreading, invasive strain has quickly become a disaster, out-competing native ladybeetle populations (some to the point of extinction), causing home infestations, decimating fruit crops, and contaminating many batches of wine with their bitter flavor after being inadvertently harvested with the grapes (Pickering et al. 2004).<\/p>\n<figure style=\"width: 583px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image13-2.png\" alt=\"One gray ladybug is migrating to the group of white ladybugs.\" width=\"583\" height=\"219\" \/><figcaption class=\"wp-caption-text\">Figure 5.13: Gene flow between two populations of ladybeetles (ladybugs). Credit: <a class=\"rId80\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Ladybug Gene Flow (Figure 4.14)<\/a> original to <a class=\"rId81\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId82\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<h3 class=\"import-Normal\"><strong>Natural Selection<\/strong><\/h3>\n<p class=\"import-Normal\">The final force of evolution is natural selection. This is the evolutionary process that Charles Darwin first brought to light, and it is what the general public typically evokes when considering the process of evolution. <strong>Natural <\/strong><strong>s<\/strong><strong>election<\/strong> occurs when certain phenotypes confer an advantage or disadvantage in survival and\/or reproductive success. The alleles associated with those phenotypes will change in frequency over time due to this selective pressure. It\u2019s also important to note that the advantageous allele may change over time (with environmental changes) and that an allele that had previously been benign may become advantageous or detrimental. Of course, dominant, recessive, and codominant traits will be selected upon a bit differently from one another. Because natural selection acts on phenotypes rather than the alleles themselves, deleterious (disadvantageous) alleles can be retained by heterozygotes without any negative effects.<\/p>\n<p class=\"import-Normal\">In the case of our primordial ocean cells, up until now, the texture of their cell membranes has been benign. The frequencies of smooth to ruffled alleles, and smooth to ruffled phenotypes, has changed over time, due to genetic drift and gene flow. Let\u2019s now imagine that the Earth\u2019s climate has cooled to a point that the waters frequently become too cold for survival of the tiny bacteria that are the dietary staples of our smooth and ruffled cell populations. The way amoeba-like cells \u201ceat\u201d is to stretch out the cell membrane, almost like an arm, to encapsulate, then ingest, the tiny bacteria. When the temperatures plummet, the tiny bacteria populations plummet with them. Larger bacteria, however, are better able to withstand the temperature change.<\/p>\n<p class=\"import-Normal\">The smooth cells were well-adapted to ingesting tiny bacteria but poorly suited to encapsulating the larger bacteria. The cells with the ruffled membranes, however, are easily able to extend their ruffles to encapsulate the larger bacteria. They also find themselves able to stretch their entire membrane to a much larger size than their smooth-surfaced neighbors, allowing them to ingest more bacteria at a given time and to go for longer periods between feedings (Figure 5.14).<\/p>\n<figure style=\"width: 528px\" class=\"wp-caption aligncenter\"><img class=\"\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image14-2.png\" alt=\"Smooth and ruffled cells feeding on large and small bacteria.\" width=\"528\" height=\"307\" \/><figcaption class=\"wp-caption-text\">Figure 5.14: Smooth and ruffled cells feeding. Credit: Smooth and ruffled cells feeding original to Explorations: An Open Invitation to Biological Anthropology (2nd ed.) by Andrea J. Alveshere is a collective work under a <a class=\"rId84\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>. [Includes <a class=\"rId85\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Cladograma_dos_Dom%C3%ADnios_e_Reinos.png\">Cladograma dos Dominios e Reinos<\/a> by <a class=\"rId86\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:MarceloTeles\">MarceloTeles<\/a> (modified), <a class=\"rId87\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a><a class=\"rId88\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">; <\/a><a class=\"rId89\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Amoeba_proteus_TK-UT.svg\">Amoeba Proteus TK-UT<\/a> by <a class=\"rId90\" href=\"https:\/\/commons.wikimedia.org\/wiki\/User:Nefronus\">Tom\u00e1\u0161 Kebert<\/a> and <a class=\"rId91\" href=\"https:\/\/www.umimeto.org\/\">umimeto.org<\/a> (modified), <a class=\"rId92\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/deed.en\">CC BY-SA 4.0<\/a>.]<\/figcaption><\/figure>\n<p class=\"import-Normal\">The smooth and ruffled traits, which had previously offered no advantage or disadvantage while food was plentiful, now are subject to natural selection. During the cold snaps, at least, the ruffled cells have a definite advantage. We can imagine that the western population that has mostly ruffled alleles will continue to do well, while the eastern population is at risk of dying out if the smaller bacteria remain scarce and no ruffled alleles are introduced.<\/p>\n<p class=\"import-Normal\">A classic example of natural selection involves the study of an insect called the <strong>peppered moth<\/strong> (<em>Biston betularia<\/em>) in England during the Industrial Revolution in the 1800s. Prior to the Industrial Revolution, the peppered moth population was predominantly light in color, with dark (pepper-like) speckles on the wings. The \u201cpeppered\u201d coloration was very similar to the appearance of the bark and lichens that grew on the local trees (Figure 5.15). This helped to camouflage the moths as they rested on a tree, making it harder for moth-eating birds to find and snack on them. There was another phenotype that popped up occasionally in the population. These individuals were heterozygotes that carried an overactive, dominant pigment allele, producing a solid black coloration. As you can imagine, the black moths were much easier for birds to spot, making this phenotype a real disadvantage.<\/p>\n<p class=\"import-Normal\">The situation changed, however, as the Industrial Revolution took off. Large factories began spewing vast amounts of coal smoke into the air, blanketing the countryside, including the lichens and trees, in black soot. Suddenly, it was the light-colored moths that were easy for birds to spot and the black moths that held the advantage. The frequency of the dark pigment allele rose dramatically. By 1895, the black moth phenotype accounted for 98% of observed moths (Grant 1999).<\/p>\n<figure style=\"width: 476px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image15-2.png\" alt=\"An illustration of natural selection.\" width=\"476\" height=\"531\" \/><figcaption class=\"wp-caption-text\">Figure 5.15: Dark and light peppered moth variants and their relative camouflage abilities on clean (top) and sooty (bottom) trees. Credit: <a class=\"rId94\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Peppered_moths_c2.jpg\">Peppered moths c2<\/a> by Khaydock is under a <a class=\"rId95\" href=\"https:\/\/creativecommons.org\/licenses\/by-sa\/3.0\/legalcode\">CC BY-SA 3.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Thanks to new environmental regulations in the 1960s, the air pollution in England began to taper off. As the soot levels decreased, returning the trees to their former, lighter color, this provided the perfect opportunity to study how the peppered moth population would respond. Repeated follow-up studies documented the gradual rise in the frequency of the lighter-colored phenotype. By 2003, the maximum frequency of the dark phenotype was 50% and in most parts of England had decreased to less than 10% (Cook 2003).<\/p>\n<h4 class=\"import-Normal\"><em>Directional, Balancing\/Stabilizing, and Disruptive\/Diversifying Selection<\/em><\/h4>\n<p class=\"import-Normal\">Natural selection can be classified as directional, balancing\/stabilizing, or disruptive\/diversifying, depending on how the pressure is applied to the population (Figure 5.16).<\/p>\n<figure style=\"width: 465px\" class=\"wp-caption aligncenter\"><img class=\"\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image16-2.png\" alt=\"Three types of selection; balancing, directional and disruptive\/diversifying\" width=\"465\" height=\"574\" \/><figcaption class=\"wp-caption-text\">Figure 5.16: Lines depict the affects of (a) Balancing\/Stabilizing, (b) Directional, and (c) Disruptive\/Diversifying selection on populations. <a href=\"https:\/\/docs.google.com\/document\/d\/1VUDKMBJYS_jNONjLxT04jQN0_z9Ua50BRN6auGSHUuU\/edit\" target=\"_blank\" rel=\"noopener\">A full text description of this image is available<\/a>. Credit: <a class=\"rId97\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Figure_19_03_01.png\">Biology (ID: 185cbf87-c72e-48f5-b51e-f14f21b5eabd@9.17)<\/a> by <a class=\"rId98\" href=\"https:\/\/cnx.org\/\">CNX OpenStax<\/a> is used under a <a class=\"rId99\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Both of the above examples of natural selection involve <strong>directional selection<\/strong>: the environmental pressures favor one phenotype over the other and cause the frequencies of the associated advantageous alleles (ruffled membranes, dark pigment) to gradually increase. In the case of the peppered moths, the direction shifted three times: first, it was selecting for lighter pigment; then, with the increase in pollution, the pressure switched to selection for darker pigment; finally, with reduction of the pollution, the selection pressure shifted back again to favoring light-colored moths.<\/p>\n<p class=\"import-Normal\"><strong>Balancing selection<\/strong> (a.k.a. stabilizing selection) occurs when selection works against the extremes of a trait and favors the intermediate phenotype. For example, humans maintain an average birth weight that balances the need for babies to be small enough not to cause complications during pregnancy and childbirth but big enough to maintain a safe body temperature after they are born. Another example of balancing selection is found in the genetic disorder called sickle cell anemia (see \u201cSpecial Topic: Sickle Cell Anemia\u201d).<\/p>\n<p class=\"import-Normal\"><strong>Disruptive selection<\/strong> (a.k.a. diversifying selection), the opposite of balancing selection, occurs when both extremes of a trait are advantageous. Since individuals with traits in the mid-range are selected against, disruptive selection can eventually lead to the population evolving into two separate species. Darwin believed that the many species of finches (small birds) found in the remote Galapagos Islands provided a clear example of disruptive selection leading to speciation. He observed that seed-eating finches either had large beaks, capable of eating very large seeds, or small beaks, capable of retrieving tiny seeds. The islands did not have many plants that produced medium-size seeds. Thus, birds with medium-size beaks would have trouble eating the very large seeds and would also have been inefficient at picking up the tiny seeds. Over time, Darwin surmised, this pressure against mid-size beaks may have led the population to divide into two separate species.<\/p>\n<h4 class=\"import-Normal\"><em>Sexual Selection<\/em><\/h4>\n<p class=\"import-Normal\"><strong>Sexual <\/strong><strong>s<\/strong><strong>election<\/strong> is an aspect of natural selection in which the selective pressure specifically affects reproductive success (the ability to successfully breed and raise offspring) rather than survival. Sexual selection favors traits that will attract a mate. Sometimes these sexually appealing traits even carry greater risks in terms of survival.<\/p>\n<figure style=\"width: 354px\" class=\"wp-caption alignleft\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image17-2.png\" alt=\"A fox chases a peacock fleeing; a peacock displays his feathers to a peahen.\" width=\"354\" height=\"413\" \/><figcaption class=\"wp-caption-text\">Figure 5.17: Showy peacock tail disadvantages (becoming easier prey) and advantages (impressing peahens). Credit: <a class=\"rId101\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Peacock tail advantage and disadvantages (Figure 4.18)<\/a> original to <a class=\"rId102\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId103\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.License.<\/figcaption><\/figure>\n<p class=\"import-Normal\">A classic example of sexual selection involves the brightly colored feathers of the peacock. The <strong>peacock<\/strong> is the male sex of the peafowl genera <em>Pavo<\/em>\u00a0and\u00a0<em>Afropavo. <\/em>During mating season, peacocks will fan their colorful tails wide and strut in front of the peahens in a grand display. The peahens will carefully observe these displays and will elect to mate with the male that they find the most appealing. Many studies have found that peahens prefer the males with the fullest, most colorful tails. While these large, showy tails provide a reproductive advantage, they can be a real burden in terms of escaping predators. The bright colors and patterns as well as the large size of the peacock tail make it difficult to hide. Once predators spot them, peacocks also struggle to fly away, with the heavy tail trailing behind and weighing them down (Figure 5.17). Some researchers have argued that the increased risk is part of the appeal for the peahens: only an especially strong, alert, and healthy peacock would be able to avoid predators while sporting such a spectacular tail.<\/p>\n<\/div>\n<p>It\u2019s important to keep in mind that sexual selection relies on the trait being present throughout mating years. Reflecting on the NF1 genetic disorder (see \u201cSpecial Topic: Neurofibromatosis Type 1 [NF1]\u201d), given how disfiguring the symptoms can become, some might find it surprising that half of the babies born with NF1 inherited it from a parent. Given that the disorder is autosomal dominant and fully penetrant (meaning it has no unaffected carriers), it may seem surprising that sexual selection doesn\u2019t exert more pressure against the mutated alleles. One important factor is that, while the neurofibromas typically begin to appear during puberty, they usually emerge only a few at a time and may grow very slowly. Many NF1 patients don\u2019t experience the more severe or disfiguring symptoms until later in life, long after they have started families of their own.<\/p>\n<p class=\"import-Normal\">Some researchers prefer to classify sexual selection separately, as a fifth force of evolution. The traits that underpin mate selection are entirely natural, of course. Research has shown that subtle traits, such as the type of pheromones (hormonal odors related to immune system alleles) someone emits and how those are perceived by the immune system genotype of the \u201csniffer,\u201d may play crucial and subconscious roles in whether we find someone attractive or not (Chaix, Cao, and Donnelly 2008).<\/p>\n<div class=\"textbox\">\n<h2 class=\"import-Normal\">Special Topic: Neurofibromatosis Type 1 (NF1)<\/h2>\n<p class=\"import-Normal\"><strong>Neurofibromatosis Type 1<\/strong>, also known as <strong>NF1<\/strong>, is a genetic disorder that illustrates how a mutation in a single gene can affect multiple systems in the body. Surprisingly common, more people have NF1 than cystic fibrosis and muscular dystrophy combined. Even more surprising, given how common it is, is how few people have heard of it. One in every 3,000 babies is born with NF1, and this holds true for all populations worldwide (Riccardi 1992). This means that, for every 3,000 people in your community, there is likely at least one person living with this disorder. NF1 is an <strong>autosomal dominant <\/strong>condition, which means that everyone born with a mutation in the gene, whether inherited or spontaneous, has a 50\/50 chance of passing it on to each of their own children.<\/p>\n<p class=\"import-Normal\">The NF1 disorder results from mutation of the <em>NF1<\/em> gene on Chromosome 17. Almost any mutation that affects the sequence of the gene\u2019s protein product, neurofibromin, will cause the disorder. Studies of individuals with NF1 have identified over 3,000 different mutations of all kinds (including point mutations, small and large indels, and translocations). The <em>NF1 <\/em>gene is one of the largest known genes, containing at least 60 <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_280_724\">exons<\/a><\/strong> (protein-encoding sequences) in a span of about 300,000 nucleotides.<\/p>\n<p class=\"import-Normal\">We know that neurofibromin plays an important role in preventing tumor growth because one of the most common symptoms of the NF1 disorder is the growth of <strong>benign <\/strong>(noncancerous) tumors, called <strong>neurofibromas<\/strong>. Neurofibromas sprout from nerve sheaths\u2014the tissues that encase our nerves\u2014throughout the body, usually beginning around puberty. There is no way to predict where the tumors will occur, or when or how quickly they will grow, although only about 15% turn <strong>malignant<\/strong> (cancerous). The two types of neurofibromas that are typically most visible are <strong>cutaneous neurofibromas<\/strong>, which are spherical bumps on, or just under, the surface of the skin (Figure 5.18), and <strong>plexiform neurofibromas<\/strong><em>, <\/em>growths involving whole branches of nerves, often giving the appearance that the surface of the skin is \u201cmelting\u201d (Figure 5.19).<\/p>\n<figure id=\"attachment_131\" aria-describedby=\"caption-attachment-131\" style=\"width: 510px\" class=\"wp-caption aligncenter\"><img class=\"wp-image-129\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/4.18.jpg\" alt=\"A woman has dozens of round, skin-colored tumors visible on her face, neck, and hand.\" width=\"510\" height=\"340\" \/><figcaption id=\"caption-attachment-131\" class=\"wp-caption-text\">Figure 5.18: A woman with many cutaneous neurofibromas, a common symptom of Neurofibromatosis Type 1. Credit: <a class=\"rId105\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Woman with cutaneous neurofibromas (symptom of NF1)<\/a> by <a class=\"rId106\" href=\"https:\/\/positiveexposure.org\/about-the-program-2\/rick-guidotti\/\">Rick Guidotti of Positive Exposure<\/a> is used with permission and is available here under a <a class=\"rId107\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<figure id=\"attachment_131\" aria-describedby=\"caption-attachment-131\" style=\"width: 1900px\" class=\"wp-caption aligncenter\"><img class=\"wp-image-130 size-full\" src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/4.19.jpg\" alt=\"An adult with large plexiform neurofibromas covering his face, none are on the child.\" width=\"1900\" height=\"700\" \/><figcaption id=\"caption-attachment-131\" class=\"wp-caption-text\">Figure 5.19: Photo on the left is of a man with large plexiform neurofibroma, another symptom of Neurofibromatosis Type 1. Photo on the right is a childhood photo of the same man, illustrating the progressive nature of the NF1 disorder. Credit: <a class=\"rId110\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Man with plexiform neurofibroma (symptom of NF1)<\/a> from Ashok Shrestha is used by permission and available here under a <a class=\"rId111\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>. <a class=\"rId112\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Childhood photo of the same man with NF1 disorder<\/a> from Ashok Shrestha is used by permission and available here under a <a class=\"rId113\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Unfortunately, there is currently no cure for NF1. Surgical removal of neurofibromas risks paralysis, due to the high potential for nerve damage, and often results in the tumors growing back even more vigorously. This means that patients are often forced to live with disfiguring and often painful neurofibromas. People who are not familiar with NF1 often mistake neurofibromas for something contagious. This makes it especially hard for people living with NF1 to get jobs working with the public or even to enjoy spending time away from home. Raising public awareness about NF1 and its symptoms can be a great help in improving the quality of life for people living with this condition.<\/p>\n<figure style=\"width: 311px\" class=\"wp-caption alignleft\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image21-2.png\" alt=\"A child with darker oval birthmarks scattered across his torso and arms.\" width=\"311\" height=\"415\" \/><figcaption class=\"wp-caption-text\">Figure 5.20: Image of a child with caf\u00e9-au-lait macules (birthmarks) typical of the earliest symptoms of NF1. Credit: <a class=\"rId115\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Child with caf\u00e9-au-lait macules (birthmarks) typical of the earliest symptoms of NF1<\/a> by Andrea J. Alveshere is under a <a class=\"rId116\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">One of the first symptoms of NF1 in a small child is usually the appearance of <strong>caf\u00e9-au-lait spots<\/strong>, or <strong>CALS<\/strong>, which are flat, brown birthmark-like spots on the skin (Figure 5.20). CALS are often light brown, similar to the color of coffee with cream, which is the reason for the name, although the shade of the pigment depends on a person\u2019s overall complexion. Some babies are born with CALS, but for others the spots appear within the first few years of life. Having six or more CALS larger than five millimeters (mm) across is a strong indicator that a child may have NF1.<\/p>\n<p class=\"import-Normal\">Other common symptoms include the following: gliomas (tumors) of the optic nerve, which can cause vision loss; thinning of bones and failure to heal if they break (often requiring amputation); low muscle tone (poor muscle development, often delaying milestones such as sitting up, crawling, and walking); hearing loss, due to neurofibromas on auditory nerves; and learning disabilities, especially those involving spatial reasoning. Approximately 50% of people with NF1 have some type of speech and\/or learning disability and often benefit greatly from early intervention services. Generalized developmental disability, however, is not common with NF1, so most people with NF1 live independently as adults. Many people with NF1 live full and successful lives, as long as their symptoms can be managed.<\/p>\n<p class=\"import-Normal\">Based on the wide variety of symptoms, it\u2019s clear that the neurofibromin protein plays important roles in many biochemical pathways. While everyone who has NF1 will exhibit some symptoms during their lifetime, there is a great deal of variation in the types and severity of symptoms, even between individuals from the same family who share the exact same NF1 mutation. It seems crazy that a gene with so many important functions would be so susceptible to mutation. Part of this undoubtedly has to do with its massive size\u2014a gene with 300,000 nucleotides has ten times more nucleotides available for mutation than does a gene of 30,000 bases. This also suggests that the mutability of this gene might provide some benefits, which is a possibility that we will revisit later in this chapter.<\/p>\n<\/div>\n<div class=\"textbox\">\n<h2 class=\"import-Normal\">Special Topic: Sickle Cell Anemia<\/h2>\n<p class=\"import-Normal\"><strong>Sickle cell anemia<\/strong> is an autosomal recessive genetic disorder that affects millions of people worldwide. It is most common in Africa, countries around the Mediterranean Sea, and eastward as far as India. Populations in the Americas that have high percentages of ancestors from these regions also have high rates of sickle cell anemia. In the United States, it\u2019s estimated that 72,000 people live with the disease, with one in approximately 1,200 Hispanic-American babies and one in every 500 African-American babies inheriting the condition (World Health Organization 1996).<\/p>\n<figure style=\"width: 344px\" class=\"wp-caption alignright\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image22-2.png\" alt=\"Round and sickle cells.\" width=\"344\" height=\"258\" \/><figcaption class=\"wp-caption-text\">Figure 5.21: Sickle cell anemia. Arrows indicate (a) sickled and (b) normal red blood cells. Credit: <a class=\"rId118\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Sickle-cell_smear_2015-09-10.jpg\">Sickle-cell smear 2015-09-10<\/a> by Paulo Henrique Orlandi Mourao has been modified (contrast modified and labels added) and is under a <a class=\"rId119\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">CC BY-NC-SA 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Sickle cell anemia affects the hemoglobin protein in red blood cells. Normal red blood cells are somewhat doughnut-shaped\u2014round with a depression on both sides of the middle. They carry oxygen around the bloodstream to cells throughout the body. Red blood cells produced by the mutated form of the gene take on a stiff, sickle-like crescent shape when stressed by low oxygen or dehydration (Figure 5.21). Because of their elongated shape and the fact that they are stiff rather than flexible, they tend to form clumps in the blood vessels, inhibiting blood flow to adjacent areas of the body. This causes episodes of extreme pain and can cause serious problems in the oxygen-deprived tissues. The sickle cells also break down much more quickly than normal cells, often lasting only 20 days rather than the 120 days of normal cells. This causes an overall shortage of blood cells in the sickle cell patient, resulting in low iron (anemia) and problems associated with it such as extreme fatigue, shortness of breath, and hindrances to children\u2019s growth and development.<\/p>\n<p class=\"import-Normal\">The devastating effects of sickle cell anemia made its high frequency a pressing mystery. Why would an allele that is so deleterious in its homozygous form be maintained in a population at levels as high as the one in twelve African Americans estimated to carry at least one copy of the allele? The answer turned out to be one of the most interesting cases of balancing selection in the history of genetic study.<\/p>\n<p class=\"import-Normal\">While looking for an explanation, scientists noticed that the countries with high rates of sickle cell disease also shared a high risk for another disease called <strong>malaria<\/strong>, which is caused by infection of the blood by a <strong><em>Plasmodium<\/em><\/strong> parasite. These parasites are carried by mosquitoes and enter the human bloodstream via a mosquito bite. Once infected, the person will experience flu-like symptoms that, if untreated, can often lead to death. Researchers discovered that many people living in these regions seemed to have a natural resistance to malaria. Further study revealed that people who carry the sickle cell allele are far less likely to experience a severe case of malaria. This would not be enough of a benefit to make the allele advantageous for the sickle cell homozygotes, who face shortened life spans due to sickle cell anemia. The real benefit of the sickle cell allele goes to the heterozygotes.<\/p>\n<p class=\"import-Normal\">People who are heterozygous for sickle cell carry one normal allele, which produces the normal, round, red blood cells, and one sickle cell allele, which produces the sickle-shaped red blood cells. Thus, they have both the sickle and round blood cell types in their bloodstream. They produce enough of the round red blood cells to avoid the symptoms of sickle cell anemia, but they have enough sickle cells to provide protection from malaria.<\/p>\n<p class=\"import-Normal\">When the <em>Plasmodium <\/em>parasites infect an individual, they begin to multiply in the liver, but then must infect the red blood cells to complete their reproductive cycle. When the parasites enter sickle-type cells, the cells respond by taking on the sickle shape. This prevents the parasite from circulating through the bloodstream and completing its life cycle, greatly inhibiting the severity of the infection in the sickle cell heterozygotes compared to non\u2013-sickle cell homozygotes. See Chapter 14 for more discussion of sickle cell anemia.<\/p>\n<\/div>\n<div class=\"textbox\">\n<h2 class=\"import-Normal\">Special Topic: The Real Primordial Cells\u2014<em>Dictyostelium Discoideum<\/em><\/h2>\n<p class=\"import-Normal\">The amoeba-like primordial cells that were used as recurring examples throughout this chapter are inspired by actual research that is truly fascinating. In 2015, Gareth Bloomfield and colleagues reported on their genomic study of the social amoeba <strong><em>Dictyostelium discoideum<\/em><\/strong> (a.k.a. \u201cslime molds,\u201d although technically they are amoebae, not molds). Strains of these amoebae have been grown in research laboratories for many decades and are useful in studying the mechanisms that amoeboid single-celled organisms use to ingest food and liquid. For simplification of our examples in this chapter, our amoeba-like cells remained ocean dwellers. Wild <em>Dictyostelium discoideum<\/em>, however, live in soil and feed on soil bacteria by growing ruffles in their membranes that reach out to encapsulate the bacterial cell. Laboratory strains, however, are typically raised on liquid media (agar) in Petri dishes, which is not suitable for the wild-type amoebae. It was widely known that the laboratory strains must have developed mutations in one or more genes to allow them to ingest the larger nutrient particles in the agar and larger volumes of liquid, but the genes involved were not known.<\/p>\n<p class=\"import-Normal\">Bloomfield and colleagues performed genomic testing on both the wild and the laboratory strains of <em>Dictyostelium discoideum. <\/em>Their discovery was astounding: every one of the laboratory strains carried a mutation in the <em>NF1 <\/em>gene, the very same gene associated with Neurofibromatosis Type 1 (NF1) in humans. The antiquity of this massive, easily mutated gene is incredible. It originated in an ancestor common to both humans and these amoebae, and it has been retained in both lineages ever since. As seen in <em>Dictyostelium discoideum<\/em>, breaking the gene can be advantageous. Without a functioning copy of the neurofibromin protein, the cell membrane is able to form much-larger feeding structures, allowing the <em>NF1 <\/em>mutants to ingest larger particles and larger volumes of liquid. For these amoebae, this may provide dietary flexibility that functions somewhat like an insurance policy for times when the food supply is limited.<\/p>\n<p class=\"import-Normal\"><em>Dictyostelium discoideum <\/em>are also interesting in that they typically reproduce asexually, but under certain conditions, one cell will convert into a \u201cgiant\u201d cell, which encapsulates surrounding cells, transforming into one of three sexes. This cell will undergo meiosis, producing gametes that must combine with one of the other two sexes to produce viable offspring. This ability for sexual reproduction may be what allows <em>Dictyostelium discoideum<\/em> to benefit from the advantages of <em>NF1<\/em> mutation, while also being able to restore the wild type <em>NF1<\/em> gene in future generations.<\/p>\n<p class=\"import-Normal\">What does this mean for humans living with NF1? Well, understanding the role of the neurofibromin protein in the membranes of simple organisms like <em>Dictyostelium discoideum<\/em> may help us to better understand how it functions and malfunctions in the sheaths of human neurons. It\u2019s also possible that the mutability of the NF1 gene confers certain advantages to humans as well. Alleles of the NF1 gene have been found to reduce one\u2019s risk for alcoholism (Repunte-Canonigo Vez et al. 2015), opiate addiction (Sanna et al. 2002), Type 2 diabetes (Martins et al. 2016), and hypomusicality (a lower-than-average musical aptitude; Cota et al. 2018). This research is ongoing and will be exciting to follow in the coming years.<\/p>\n<\/div>\n<h2 class=\"__UNKNOWN__\">Studying Evolution in Action<\/h2>\n<div class=\"__UNKNOWN__\">\n<h3 class=\"import-Normal\"><strong>The Hardy-Weinberg Equilibrium <\/strong><\/h3>\n<p class=\"import-Normal\">This chapter has introduced you to the forces of evolution, the mechanisms by which evolution occurs. How do we detect and study evolution, though, in real time, as it happens? One tool we use is the <strong>Hardy-<\/strong><strong>Weinberg<\/strong><strong> Equilibrium<\/strong>: a mathematical formula that allows estimation of the number and distribution of dominant and recessive alleles in a population. This aids in determining whether allele frequencies are changing and, if so, how quickly over time, and in favor of which allele? It\u2019s important to note that the Hardy-Weinberg formula only gives us an estimate based on the data for a snapshot in time. We will have to calculate it again later, after various intervals, to determine if our population is evolving and in what way the allele frequencies are changing.<\/p>\n<h3 class=\"import-Normal\">Calculating the Hardy-Weinberg Equilibrium<\/h3>\n<p class=\"import-Normal\">In the Hardy-Weinberg formula, <em>p <\/em>represents the frequency of the dominant allele, and <em>q<\/em> represents the frequency of the recessive allele. Remember, an allele\u2019s frequency is the proportion, or percentage, of that allele in the population. For the purposes of Hardy-Weinberg, we give the allele percentages as decimal numbers (e.g., 42% = 0.42), with the entire population (100% of alleles) equaling 1. If we can figure out the frequency of one of the alleles in the population, then it is simple to calculate the other. Simply subtract the known frequency from 1 (the entire population): 1<em> \u2013 p = q<\/em> and 1<em> \u2013 q = p<\/em>.<\/p>\n<p class=\"import-Normal\">The Hardy-Weinberg formula is <em>p<\/em><sup><em>2<\/em><\/sup><em> + 2pq + q<\/em><sup><em>2<\/em><\/sup>, where:<\/p>\n<p class=\"import-Normal\" style=\"padding-left: 40px\"><em>p<\/em><sup><em>2<\/em><\/sup> represents the frequency of the homozygous dominant genotype;<\/p>\n<p class=\"import-Normal\" style=\"padding-left: 40px\"><em>2pq<\/em> represents the frequency of the heterozygous genotype; and<\/p>\n<p class=\"import-Normal\" style=\"padding-left: 40px\"><em>q<\/em><sup><em>2<\/em><\/sup> represents the frequency of the homozygous recessive genotype.<\/p>\n<p class=\"import-Normal\">It is often easiest to determine <em>q<\/em><sup><em>2<\/em><\/sup> first, simply by counting the number of individuals with the unique, homozygous recessive phenotype (then dividing by the total individuals in the population to arrive at the \u201cfrequency\u201d). Once we have this number, we simply need to calculate the square root of the homozygous recessive phenotype frequency. That gives us <em>q.<\/em> Remember, 1 <em>\u2013<\/em> <em>q <\/em>equals <em>p<\/em>, so now we have the frequencies for both alleles in the population. If we needed to figure out the frequencies of heterozygotes and homozygous dominant genotypes, we\u2019d just need to plug the <em>p<\/em> and <em>q<\/em> frequencies back into the <em>p<\/em><sup><em>2<\/em><\/sup> and 2<em>pq<\/em> formulas.<\/p>\n<figure style=\"width: 329px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image25-1.png\" alt=\"A circle with seven grey and three white ladybugs.\" width=\"329\" height=\"347\" \/><figcaption class=\"wp-caption-text\">Figure 5.24: Ladybug population with a mixture of dark (red) and light (orange) individuals. Credit: <a class=\"rId129\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Ladybug mix (Figure 4.21)<\/a> original to <a class=\"rId130\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId131\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Let\u2019s imagine we have a population of ladybeetles that carries two alleles: a dominant allele that produces red ladybeetles and a recessive allele that produces orange ladybeetles. Since red is dominant, we\u2019ll use <em>R <\/em>to represent the red allele, and <em>r <\/em>to represent the orange allele. Our population has ten beetles, and seven are red and three are orange (Figure 5.24). Let\u2019s calculate the number of genotypes and alleles in this population.<\/p>\n<p class=\"import-Normal\">Of ten total beetles, we have three orange beetles3\/10 = .30 (30%) frequency\u2014and we know they are homozygous recessive (<em>rr<\/em>). So:<\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\"><em>rr = .3; <\/em>therefore, <em>r = <\/em>\u221a.3 = .5477<\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\"><em>R<\/em> = 1 <em>\u2013<\/em> .5477 = .4523<\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\">Using the Hardy-Weinberg formula:<\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\">1=.4523<sup>2 <\/sup>+ 2 x .4523 x .5477 +.5477<sup>2 <\/sup>= .20 + .50 + .30 = 1<\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\">Thus, the genotype breakdown is 20% <em>RR, <\/em>50%<em> Rr, <\/em>and 30%<em> rr <\/em><\/p>\n<p class=\"import-Normal\" style=\"text-indent: 36pt\">(2 red homozygotes, 5 red heterozygotes, and 3 orange homozygotes).<\/p>\n<p class=\"import-Normal\">Since we have 10 individuals, we know we have 20 total alleles: 4 red from the <em>RR<\/em> group, 5 red and 5 orange from the <em>Rr<\/em> group, and 6 orange from the <em>rr<\/em> group, for a grand total of 9 red and 11 orange (45% red and 55% orange, just like we estimated in the 1 \u2013 <em>q <\/em>step).<\/p>\n<p class=\"import-Normal\">Reminder: The Hardy-Weinberg formula only gives us an estimate for a snapshot in time. We will have to calculate it again later, after various intervals, to determine if our population is evolving and in what way the allele frequencies are changing.<\/p>\n<h3 class=\"import-Normal\"><strong>Interpreting Evolutionary Change: Nonra<\/strong><strong>ndom Mating <\/strong><\/h3>\n<p class=\"import-Normal\">Once we have detected change occurring in a population, we need to consider which evolutionary processes might be the cause of the change. It is important to watch for nonrandom mating patterns, to see if they can be included or excluded as possible sources of variation in allele frequencies.<\/p>\n<p class=\"import-Normal\"><strong>Nonrandom <\/strong><strong>m<\/strong><strong>ating<\/strong> (also known as assortative mating) occurs when mate choice within a population follows a nonrandom pattern.<\/p>\n<p class=\"import-Normal\"><strong>Positive assortative mating<\/strong> patterns result from a tendency for individuals to mate with others who share similar phenotypes. This often happens based on body size. Taking as an example dog breeds, it is easier for two Chihuahuas to mate and have healthy offspring than it is for a Chihuahua and a St. Bernard to do so. This is especially true if the Chihuahua is the female and would have to give birth to giant St. Bernard pups.<\/p>\n<p class=\"import-Normal\"><strong>Negative assortative mating<\/strong> patterns occur when individuals tend to select mates with qualities different from their own. This is what is at work when humans choose partners whose pheromones indicate that they have different and complementary immune alleles, providing potential offspring with a better chance at a stronger immune system.<\/p>\n<p class=\"import-Normal\">Among domestic animals, such as pets and livestock, assortative mating is often directed by humans who decide which pairs will mate to increase the chances of offspring having certain desirable traits. This is known as <strong>a<\/strong><strong>rtificial <\/strong><strong>s<\/strong><strong>election<\/strong><em>.<\/em><\/p>\n<p class=\"import-Normal\">Among humans, in addition to phenotypic traits, cultural traits such as religion and ethnicity may also influence assortative mating patterns.<\/p>\n<h3 class=\"import-Normal\"><strong>Defining a Species<\/strong><\/h3>\n<p class=\"import-Normal\"><em>Species<\/em> are organisms whose individuals are capable of breeding because they are biologically and behaviorally compatible to produce viable, fertile offspring. <strong>Viable offspring<\/strong> are those offspring that are healthy enough to survive to adulthood. <strong>Fertile offspring<\/strong> are able to reproduce successfully, resulting in offspring of their own. Both conditions must be met for individuals to be considered part of the same species. As you can imagine, these criteria complicate the identification of distinct species in fossilized remains of extinct populations. In those cases, we must examine how much phenotypic variation is typically found within a comparable modern-day species; we can then determine whether the fossilized remains fall within the expected range of variation for a single species.<\/p>\n<p class=\"import-Normal\">Some species have subpopulations that are regionally distinct. These are classified as separate <strong>subspecies<\/strong> because they have their own unique phenotypes and are geographically isolated from one another. However, if they do happen to encounter one another, they are still capable of successful interbreeding.<\/p>\n<p class=\"import-Normal\">There are many examples of sterile hybrids that are offspring of parents from two different species. For example, horses and donkeys can breed and have offspring together. Depending on which species is the mother and which is the father, the offspring are either called mules, or hennies. Mules and hennies can live full life spans but are not able to have offspring of their own. Likewise, tigers and lions have been known to mate and have viable offspring. Again, depending on which species is the mother and which is the father, these offspring are called either ligers or tigons. Like mules and hennies, ligers and tigons are unable to reproduce. In each of these cases, the mismatched set of chromosomes that the offspring inherit produce an adequate set of functioning genes for the hybrid offspring; however, once mixed and divided in meiosis, the gametes don\u2019t contain the full complement of genes needed for survival in the third generation.<\/p>\n<h3 class=\"import-Normal\"><strong>Micro- to Macroevolution<\/strong><\/h3>\n<p class=\"import-Normal\"><strong>Microevolution<\/strong> refers to changes in allele frequencies within breeding populations\u2014that is, within single species. <strong>Macroevolution<\/strong> describes how the similarities and differences between species, as well as the phylogenetic relationships with other taxa, lead to changes that result in the emergence of new species. Consider our example of the peppered moth that illustrated microevolution over time, via directional selection favoring the peppered allele when the trees were clean and the dark pigment allele when the trees were sooty. Imagine that environmental regulations had cleaned up the air pollution in one part of the nation, while the coal-fired factories continued to spew soot in another area. If this went on long enough, it\u2019s possible that two distinct moth populations would eventually emerge\u2014one containing only the peppered allele and the other only harboring the dark pigment allele.<\/p>\n<p class=\"import-Normal\">When a single population divides into two or more separate species, it is called <strong>speciation<\/strong>. The changes that prevent successful breeding between individuals who descended from the same ancestral population may involve chromosomal rearrangements, changes in the ability of the sperm from one species to permeate the egg membrane of the other species, or dramatic changes in hormonal schedules or mating behaviors that prevent members from the new species from being able to effectively pair up.<\/p>\n<p class=\"import-Normal\">There are two types of speciation: allopatric and sympatric. <strong>Allopatric speciation<\/strong> is caused by long-term <strong>isolation<\/strong> (physical separation) of subgroups of the population (Figure 5.22). Something occurs in the environment\u2014perhaps a river changes its course and splits the group, preventing them from breeding with members on the opposite riverbank. Over many generations, new mutations and adaptations to the different environments on each side of the river may drive the two subpopulations to change so much that they can no longer produce fertile, viable offspring, even if the barrier is someday removed.<\/p>\n<figure style=\"width: 1000px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image23-2.png\" alt=\"Process of isolation leading to speciation, as described in the figure caption.\" width=\"1000\" height=\"379\" \/><figcaption class=\"wp-caption-text\">Figure 5.22: Isolation leading to speciation: a. original population before isolation; b. a barrier divides the population and prevents interbreeding between the two groups; c. time passes, and the populations become genetically distinct; d. after many generations, the two populations are no longer biologically or behaviorally compatible, thus can no longer interbreed, even if the barrier is removed. Credit: <a class=\"rId121\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Isolation Leading to Speciation (Figure 4.19)<\/a> original to <a class=\"rId122\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId123\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\"><strong>Sympatric speciation<\/strong> occurs when the population splits into two or more separate species while remaining located together <em>without<\/em> a physical barrier. This typically results from a new mutation that pops up among some members of the population that prevents them from successfully reproducing with anyone who does not carry the same mutation. This is seen particularly often in plants, as they have a higher frequency of chromosomal duplications.<\/p>\n<p class=\"import-Normal\">One of the quickest rates of speciation is observed in the case of adaptive radiation. <strong>Adaptive radiation<\/strong> refers to the situation in which subgroups of a single species rapidly diversify and adapt to fill a variety of ecological niches. An <strong>e<\/strong><strong>cological niche<\/strong> is a set of constraints and resources that is available in an environmental setting. Evidence for adaptive radiations is often seen after population bottlenecks. A mass disaster kills off many species, and the survivors have access to a new set of territories and resources that were either unavailable or much coveted and fought over before the disaster. The offspring of the surviving population will often split into multiple species, each of which stems from members in that first group of survivors who happened to carry alleles that were advantageous for a particular niche.<\/p>\n<p class=\"import-Normal\">The classic example of adaptive radiation brings us back to Charles Darwin and his observations of the many species of finches on the Galapagos Islands. We are still not sure how the ancestral population of finches first arrived on that remote Pacific Island chain, but they found themselves in an environment filled with various insects, large and tiny seeds, fruit, and delicious varieties of cactus. Some members of that initial population carried alleles that gave them advantages for each of these dietary niches. In subsequent generations, others developed new mutations, some of which were beneficial. These traits were selected for, making the advantageous alleles more common among their offspring. As the finches spread from one island to the next, they would be far more likely to find mates among the birds on their new island. Birds feeding in the same area were then more likely to mate together than birds who have different diets, contributing to additional assortative mating. Together, these evolutionary mechanisms caused rapid speciation that allowed the new species to make the most of the various dietary niches (Figure 5.23).<\/p>\n<figure style=\"width: 619px\" class=\"wp-caption aligncenter\"><img src=\"http:\/\/opentextbooks.concordia.ca\/wp-content\/uploads\/sites\/71\/2025\/07\/image24-1.png\" alt=\"A family tree of finches with different sized beaks.\" width=\"619\" height=\"325\" \/><figcaption class=\"wp-caption-text\">Figure 5.23: Darwin\u2019s finches demonstrating Adaptive Radiation. Credit: <a class=\"rId125\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/chapter\/__unknown__-3\/\">Darwin\u2019s finches (Figure 4.20)<\/a> original to <a class=\"rId126\" href=\"https:\/\/pressbooks-dev.oer.hawaii.edu\/explorationsbioanth\/\">Explorations: An Open Invitation to Biological Anthropology<\/a> by Mary Nelson is under a <a class=\"rId127\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC 4.0 License<\/a>.<\/figcaption><\/figure>\n<p class=\"import-Normal\">In today\u2019s modern world, understanding these evolutionary processes is crucial for developing immunizations and antibiotics that can keep up with the rapid mutation rate of viruses and bacteria. This is also relevant to our food supply, which relies, in large part, on the development of herbicides and pesticides that keep up with the mutation rates of pests and weeds. Viruses, bacteria, agricultural pests, and weeds have all shown great flexibility in developing alleles that make them resistant to the latest medical treatment, pesticide, or herbicide. Billion-dollar industries have specialized in trying to keep our species one step ahead of the next mutation in the pests and infectious diseases that put our survival at risk.<\/p>\n<div class=\"textbox shaded\">\n<h2 class=\"import-Normal\">Review Questions<strong><br \/>\n<\/strong><\/h2>\n<ul>\n<li>Summarize the Modern Synthesis and provide several examples of how it is relevant to questions and problems in our world today.<\/li>\n<li>You inherit a house from a long-lost relative that contains a fancy aquarium, filled with a variety of snails. The phenotypes include large snails and small snails; red, black, and yellow snails; and solid, striped, and spotted snails. Devise a series of experiments that would help you determine how many snail species are present in your aquarium.<\/li>\n<li>Match the correct force of evolution with the correct real-world example:<br \/>\na. Mutationi. 5-alpha reductase deficiency<br \/>\nb. Genetic Driftii. Peppered Moths<br \/>\nc. Gene Flowiii. Neurofibromatosis Type 1<br \/>\nd. Natural Selectioniv. Scutellata Honey Bees<\/li>\n<li>Imagine a population of common house mice (<em>Mus musculus<\/em>). Draw a comic strip illustrating how mutation, genetic drift, gene flow, and natural selection might transform this population over several (or more) generations.<\/li>\n<li>\n<p class=\"import-Normal\">The many breeds of the single species of domestic dog (<em>Canis<\/em> <em>familiaris<\/em>) provide an extreme example of microevolution. Discuss why this is the case. What future scenarios can you imagine that could potentially transform the domestic dog into an example of macroevolution?<\/p>\n<\/li>\n<li>\n<p class=\"import-Normal\">The ability to roll one\u2019s tongue (lift the outer edges of the tongue to touch each other, forming a tube) is a dominant trait. In a small town of 1,500 people, 500 can roll their tongues. Use the Hardy-Weinberg formula to determine how many individuals in the town are homozygous dominant, heterozygous, and homozygous recessive.<\/p>\n<\/li>\n<\/ul>\n<\/div>\n<h2 class=\"import-Normal\">Key Terms<strong><br \/>\n<\/strong><\/h2>\n<p class=\"import-Normal\"><strong>5-alpha reductase deficiency<\/strong>: An autosomal recessive syndrome that manifests when a child having both X and Y sex chromosomes inherits two nonfunctional (mutated) copies of the SRD5A2 gene, producing a deficiency in a hormone necessary for development in infancy of typical male genitalia. These children often appear at birth to have female genitalia, but they develop a penis and other sexual characteristics when other hormones kick in during puberty.<\/p>\n<p class=\"import-Normal\"><strong>Adaptive radiation<\/strong>: The situation in which subgroups of a single species rapidly diversify and adapt to fill a variety of ecological niches.<\/p>\n<p class=\"import-Normal\"><strong>Admixture<\/strong>: A term often used to describe gene flow between human populations. Sometimes also used to describe gene flow between nonhuman populations.<\/p>\n<p class=\"import-Normal\"><strong>Allele frequency<\/strong>: The ratio, or percentage, of one allele compared to the other alleles for that gene within the study population.<\/p>\n<p class=\"import-Normal\"><strong>Alleles<\/strong>: Variant forms of genes.<\/p>\n<p class=\"import-Normal\"><strong>Allopatric speciation<\/strong>: Speciation caused by long-term isolation (physical separation) of subgroups of the population.<\/p>\n<p class=\"import-Normal\"><strong>Antibiotics<\/strong>: Medicines prescribed to treat bacterial infections.<\/p>\n<p class=\"import-Normal\"><strong>Artificial selection<\/strong>: Human-directed assortative mating among domestic animals, such as pets and livestock, designed to increase the chances of offspring having certain desirable traits.<\/p>\n<p class=\"import-Normal\"><strong>Asexual reproduction<\/strong>: Reproduction via mitosis, whereby offspring are clones of the parents.<\/p>\n<p class=\"import-Normal\"><strong>Autosomal dominant<\/strong>: A phenotype produced by a gene on an autosomal chromosome that is expressed, to the exclusion of the recessive phenotype, in heterozygotes.<\/p>\n<p class=\"import-Normal\"><strong>Autosomal recessive<\/strong>: A phenotype produced by a gene on an autosomal chromosome that is expressed only in individuals homozygous for the recessive allele.<\/p>\n<p class=\"import-Normal\"><strong>Balanced translocations<\/strong>: Chromosomal translocations in which the genes are swapped but no genetic information is lost.<\/p>\n<p class=\"import-Normal\"><strong>Balancing selection<\/strong>: A pattern of natural selection that occurs when the extremes of a trait are selected against, favoring the intermediate phenotype (a.k.a. stabilizing selection).<\/p>\n<p class=\"import-Normal\"><strong>Beneficial mutations<\/strong>: Mutations that produce some sort of an advantage to the individual.<\/p>\n<p class=\"import-Normal\"><strong>Benign<\/strong>: Noncancerous. Benign tumors may cause problems due to the area in which they are located (e.g., they might put pressure on a nerve or brain area), but they will not release cells that aggressively spread to other areas of the body.<\/p>\n<p class=\"import-Normal\"><strong>Caf\u00e9-au-lait spots (CALS)<\/strong>: Flat, brown birthmark-like spots on the skin, commonly associated with Neurofibromatosis Type 1.<\/p>\n<p class=\"import-Normal\"><strong>Chromosomal translocations<\/strong>: The transfer of DNA between nonhomologous chromosomes.<\/p>\n<p class=\"import-Normal\"><strong>Chromosomes<\/strong>: Molecules that carry collections of genes.<\/p>\n<p class=\"import-Normal\"><strong>Codons<\/strong>: Three-nucleotide units of DNA that function as three-letter \u201cwords,\u201d encoding instructions for the addition of one amino acid to a protein or indicating that the protein is complete.<\/p>\n<p class=\"import-Normal\"><strong>Cretaceous\u2013Paleogene extinction<\/strong>: A mass disaster caused by an asteroid that struck the earth approximately 66 million years ago and killed 75% of life on Earth, including all terrestrial dinosaurs. (a.k.a. K-Pg Extinction, Cretatious-Tertiary Extinction, and K-T Extinction).<\/p>\n<p class=\"import-Normal\"><strong>Crossover events<\/strong>: Chromosomal alterations that occur when DNA is swapped between homologous chromosomes while they are paired up during meiosis I.<\/p>\n<p class=\"import-Normal\"><strong>Cutaneous neurofibromas<\/strong>: Neurofibromas that manifest as spherical bumps on or just under the surface of the skin.<\/p>\n<p class=\"import-Normal\"><strong>Deleterious mutation<\/strong>: A mutation producing negative effects to the individual such as the beginnings of cancers or heritable disorders.<\/p>\n<p class=\"import-Normal\"><strong>Deletions<\/strong>: Mutations that involve the removal of one or more nucleotides from a DNA sequence.<\/p>\n<p class=\"import-Normal\"><strong>Derivative chromosomes<\/strong>: New chromosomal structures resulting from translocations.<\/p>\n<p class=\"import-Normal\"><strong><em>Dictyostelium discoideum<\/em><\/strong>: A species of social amoebae that has been widely used for laboratory research. Laboratory strains of <em>Dictyostelium discoideum <\/em>all carry mutations in the <em>NF1<\/em> gene, which is what allows them to survive on liquid media (agar) in Petri dishes.<\/p>\n<p class=\"import-Normal\"><strong>Directional selection<\/strong>: A pattern of natural selection in which one phenotype is favored over the other, causing the frequencies of the associated advantageous alleles to gradually increase.<\/p>\n<p class=\"import-Normal\"><strong>Disruptive selection<\/strong>: A pattern of natural selection that occurs when both extremes of a trait are advantageous and intermediate phenotypes are selected against (a.k.a. diversifying selection).<\/p>\n<p class=\"import-Normal\"><strong>DNA repair mechanisms<\/strong>: Enzymes that patrol and repair DNA in living cells.<\/p>\n<p class=\"import-Normal\"><strong>DNA transposons<\/strong>: Transposons that are clipped out of the DNA sequence itself and inserted elsewhere in the genome.<\/p>\n<p class=\"import-Normal\"><strong>Ecological niche<\/strong>: A set of constraints and resources that are available in an environmental setting.<\/p>\n<p class=\"import-Normal\"><strong>Ellis-van Creveld syndrome<\/strong>: An autosomal recessive disorder characterized by short stature (dwarfism), polydactyly (the development of more than five digits [fingers or toes] on the hands or feet), abnormal tooth development, and heart defects. Estimated to affect approximately one in 60,000 individuals worldwide, among the Old Order Amish of Lancaster County, the rate is estimated to be as high as one in every 200 births.<\/p>\n<p class=\"import-Normal\"><strong>Evolution<\/strong>: A change in the allele frequencies in a population over time.<\/p>\n<p class=\"import-Normal\"><strong>Exons<\/strong>: The DNA sequences within a gene that directly encode protein sequences. After being transcribed into messenger RNA, the introns (DNA sequences within a gene that do not directly encode protein sequences) are clipped out, and the exons are pasted together prior to translation.<\/p>\n<p class=\"import-Normal\"><strong>Fertile offspring<\/strong>: Offspring that can successfully reproduce, resulting in offspring of their own.<\/p>\n<p class=\"import-Normal\"><strong>Founder effect<\/strong>: A type of genetic drift that occurs when members of a population leave the main or \u201cparent\u201d group and form a new population that no longer interbreeds with the other members of the original group.<\/p>\n<p class=\"import-Normal\"><strong>Frameshift mutations<\/strong>: Types of indels that involve the insertion or deletion of any number of nucleotides that is not a multiple of three. These \u201cshift the reading frame\u201d and cause all codons beyond the mutation to be misread.<\/p>\n<p class=\"import-Normal\"><strong>Gametes<\/strong>: The reproductive cells, produced through meiosis (a.k.a. germ cells or sperm or egg cells).<\/p>\n<p class=\"import-Normal\"><strong>Gene<\/strong>: A sequence of DNA that provides coding information for the construction of proteins.<\/p>\n<p class=\"import-Normal\"><strong>Gene flow<\/strong>: The movement of alleles from one population to another. This is one of the forces of evolution.<\/p>\n<p class=\"import-Normal\"><strong>Gene pool<\/strong>: The entire collection of genetic material in a breeding community that can be passed on from one generation to the next.<\/p>\n<p class=\"import-Normal\"><strong>Genetic drift<\/strong>: Random changes in allele frequencies within a population from one generation to the next. This is one of the forces of evolution.<\/p>\n<p class=\"import-Normal\"><strong>Genotype<\/strong>: The set of alleles that an individual has for a given gene.<\/p>\n<p class=\"import-Normal\"><strong>Genotype frequencies<\/strong>: The ratios or percentages of the different homozygous and heterozygous genotypes in the population.<\/p>\n<p class=\"import-Normal\"><strong><em>Guevedoces<\/em><\/strong>: The term coined locally in the Dominican Republic for the condition scientifically known as 5-alpha reductase deficiency. The literal translation is \u201cpenis at twelve.\u201d<\/p>\n<p class=\"import-Normal\"><strong>Hardy-Weinberg Equilibrium<\/strong>: A mathematical formula (<em>1=p<\/em><sup><em>2<\/em><\/sup><em> + 2pq + q<\/em><sup><em>2<\/em><\/sup> ) that allows estimation of the number and distribution of dominant and recessive alleles in a population.<\/p>\n<p class=\"import-Normal\"><strong>Harlequin ladybeetle<\/strong>: A species of ladybeetle, native to East Asia, that was introduced to Europe and the Americas as a form of pest control. After many decades of use, one of the North American strains developed the ability to reproduce in diverse environments, causing it to spread rapidly throughout the Americas, Europe, and Africa. It has hybridized with European strains and is now a major pest in its own right.<\/p>\n<p class=\"import-Normal\"><strong>Heterozygous genotype<\/strong>: A genotype comprising two different alleles.<\/p>\n<p class=\"import-Normal\"><strong>Homozygous genotype<\/strong>: A genotype comprising an identical set of alleles.<\/p>\n<p class=\"import-Normal\"><strong>Hybridization<\/strong>: A term often used to describe gene flow between nonhuman populations.<\/p>\n<p class=\"import-Normal\"><strong>Inbreeding<\/strong>: The selection of mates exclusively from within a small, closed population.<\/p>\n<p class=\"import-Normal\"><strong>Indels<\/strong>: A class of mutations that includes both insertions and deletions.<\/p>\n<p class=\"import-Normal\"><strong>Inherited mutation<\/strong>: A mutation that has been passed from parent to offspring.<\/p>\n<p class=\"import-Normal\"><strong>Insertions<\/strong>: Mutations that involve the addition of one or more nucleotides into a DNA sequence.<\/p>\n<p class=\"import-Normal\"><strong>Isolation<\/strong>: Prevention of a population subgroup from breeding with other members of the same species due to a physical barrier or, in humans, a cultural rule.<\/p>\n<p class=\"import-Normal\"><strong>Last Universal Common Ancestor (LUCA)<\/strong>: The ancient organism from which all living things on Earth are descended.<\/p>\n<p class=\"import-Normal\"><strong>Macroevolution<\/strong>: Changes that result in the emergence of new species, how the similarities and differences between species, as well as the phylogenetic relationships with other taxa, lead to changes that result in the emergence of new species.<\/p>\n<p class=\"import-Normal\"><strong>Malaria<\/strong>: A frequently deadly mosquito-borne disease caused by infection of the blood by a <em>Plasmodium<\/em> parasite.<\/p>\n<p class=\"import-Normal\"><strong>Malignant<\/strong>: Cancerous. Malignant tumors grow aggressively and their cells may metastasize (travel through the blood or lymph systems) to form new, aggressive tumors in other areas of the body.<\/p>\n<p class=\"import-Normal\"><strong>Microevolution<\/strong>: Changes in allele frequencies within breeding populations\u2014that is, within a single species.<\/p>\n<p class=\"import-Normal\"><strong>Modern Synthesis<\/strong>: The integration of Darwin\u2019s, Mendel\u2019s, and subsequent research into a unified theory of evolution.<\/p>\n<p class=\"import-Normal\"><strong>Monosomies<\/strong>: Conditions resulting from a nondisjunction event, in which a cell ends up with only one copy of a chromosome. In humans, a single X chromosome is the only survivable monosomy.<\/p>\n<p class=\"import-Normal\"><strong>Mutation<\/strong>: A change in the nucleotide sequence of the genetic code. This is one of the forces of evolution.<\/p>\n<p class=\"import-Normal\"><strong>Natural selection<\/strong>: An evolutionary process that occurs when certain phenotypes confer an advantage or disadvantage in survival and\/or reproductive success. This is one of the forces of evolution, and it was first identified by Charles Darwin.<\/p>\n<p class=\"import-Normal\"><strong>Negative assortative mating<\/strong>: A pattern that occurs when individuals tend to select mates with qualities different from their own.<\/p>\n<p class=\"import-Normal\"><strong>Neurofibromas<\/strong>: Nerve sheath tumors that are common symptoms of Neurofibromatosis Type 1.<\/p>\n<p class=\"import-Normal\"><strong>Neurofibromatosis Type 1<\/strong>: An autosomal dominant genetic disorder affecting one in every 3,000 people. It is caused by mutation of the <em>NF1<\/em> gene on Chromosome 17, resulting in a defective neurofibromin protein. The disorder is characterized by neurofibromas, caf\u00e9-au-lait spots, and a host of other potential symptoms.<\/p>\n<p class=\"import-Normal\"><strong>NF1<\/strong>: An abbreviation for Neurofibromatosis Type 1. When italicized, <em>NF1 <\/em>refers to the gene on Chromosome 17 that encodes the neurofibromin protein.<\/p>\n<p class=\"import-Normal\"><strong>Nondisjunction events<\/strong>: Chromosomal abnormalities that occur when the homologous chromosomes (in meiosis I) or sister chromatids (in meiosis II and mitosis) fail to separate after pairing. The result is that both chromosomes or chromatids end up in the same daughter cell, leaving the other daughter cell without any copy of that chromosome.<\/p>\n<p class=\"import-Normal\"><strong>Nonrandom mating<\/strong>: A scenario in which mate choice within a population follows a nonrandom pattern (a.k.a. assortative mating).<\/p>\n<p class=\"import-Normal\"><strong>Nonsynonymous mutation<\/strong>: A point mutation that causes a change in the resulting protein.<\/p>\n<p class=\"import-Normal\"><strong>Old Order Amish<\/strong>: A culturally isolated population in Lancaster County, Pennsylvania, that has approximately 50,000 current members, all of whom can trace their ancestry back to a group of approximately eighty individuals. This group has high rates of certain genetics disorders, including Ellis-van Creveld syndrome.<\/p>\n<p class=\"import-Normal\"><strong>Origins of life<\/strong>: How the first living organism came into being.<\/p>\n<p class=\"import-Normal\"><strong>Peacock<\/strong>: The male sex of the peafowl, famous for its large, colorful tail, which it dramatically displays to attract mates. (The female of the species is known as a peahen.)<\/p>\n<p class=\"import-Normal\"><strong>Peppered moth<\/strong>: A species of moth (<em>Biston betularia<\/em>) found in England that has light and dark phenotypes. During the Industrial Revolution, when soot blackened the trees, the frequency of the previously rare dark phenotype dramatically increased, as lighter-colored moths were easier for birds to spot against the sooty trees. After environmental regulations eliminated the soot, the lighter-colored phenotype gradually became most common again.<\/p>\n<p class=\"import-Normal\"><strong>Phenotype<\/strong>: The observable traits that are produced by a genotype.<\/p>\n<p class=\"import-Normal\"><strong>Phylogenetic tree of life<\/strong>: A family tree of all living organisms, based on genetic relationships.<\/p>\n<p class=\"import-Normal\"><strong>Phylogenies<\/strong>: Genetically determined family lineages.<\/p>\n<p class=\"import-Normal\"><strong><em>Plasmodium<\/em><\/strong>: A genus of mosquito-borne parasite. Several <em>Plasmodium<\/em> species cause malaria when introduced to the human bloodstream via a mosquito bite.<\/p>\n<p class=\"import-Normal\"><strong>Plexiform neurofibromas<\/strong>: Neurofibromas that involve whole branches of nerves, often giving the appearance that the surface of the skin is \u201cmelting.\u201d<\/p>\n<p class=\"import-Normal\"><strong>Point mutation<\/strong>: A single-letter (single-nucleotide) change in the genetic code, resulting in the substitution of one nucleic acid base for a different one.<\/p>\n<p class=\"import-Normal\"><strong>Polymorphisms<\/strong>: Multiple forms of a trait; alternative phenotypes within a given species.<\/p>\n<p class=\"import-Normal\"><strong>Population<\/strong>: A group of individuals who are genetically similar enough and geographically near enough to one another that they can breed and produce new generations of individuals.<\/p>\n<p class=\"import-Normal\"><strong>Population bottleneck<\/strong>: A type of genetic drift that occurs when the number of individuals in a population drops dramatically due to some random event.<\/p>\n<p class=\"import-Normal\"><strong>Positive assortative mating<\/strong>: A pattern that results from a tendency for individuals to mate with others who share similar phenotypes.<\/p>\n<p class=\"import-Normal\"><strong>Retrotransposons<\/strong>: Transposons that are transcribed from DNA into RNA, and then are \u201creverse transcribed,\u201d to insert the copied sequence into a new location in the DNA.<\/p>\n<p class=\"import-Normal\"><strong>Scutellata honey bees<\/strong>: A strain of honey bees that resulted from the hybridization of African and European honey bee subspecies. These bees were accidentally released into the wild in 1957 in Brazil and have since spread throughout South and Central America and into the United States. Also known as \u201ckiller bees,\u201d they tend to be very aggressive in defense of their hives and have caused many fatal injuries to humans and livestock.<\/p>\n<p class=\"import-Normal\"><strong>Sexual reproduction<\/strong>: Reproduction via meiosis and combination of gametes. Offspring inherit genetic material from both parents.<\/p>\n<p class=\"import-Normal\"><strong>Sexual selection<\/strong>: An aspect of natural selection in which the selective pressure specifically affects reproductive success (the ability to successfully breed and raise offspring).<\/p>\n<p class=\"import-Normal\"><strong>Sickle cell anemia<\/strong>: An autosomal recessive genetic disorder that affects millions of people worldwide. It is most common in Africa, countries around the Mediterranean Sea, and eastward as far as India. Homozygotes for the recessive allele develop the disorder, which produce misshapen red blood cells that cause iron deficiency, painful episodes of oxygen-deprivation in localized tissues, and a host of other symptoms. In heterozygotes, though, the sickle cell allele confers a greater resistance to malaria.<\/p>\n<p class=\"import-Normal\"><strong>Somatic cells<\/strong>: The cells of our organs and other body tissues (all cells except gametes) that replicate by mitosis.<\/p>\n<p class=\"import-Normal\"><strong>Speciation<\/strong>: The process by which a single population divides into two or more separate species.<\/p>\n<p class=\"import-Normal\"><strong>Species<\/strong>: Organisms whose individuals are capable of breeding because they are biologically and behaviorally compatible to produce viable, fertile offspring.<\/p>\n<p class=\"import-Normal\"><strong>Spontaneous mutation<\/strong>: A mutation that occurs due to random chance or unintentional exposure to mutagens. In families, a spontaneous mutation is the first case, as opposed to mutations that are inherited from parents.<\/p>\n<p class=\"import-Normal\"><strong>Subspecies<\/strong>: A distinct subtype of a species. Most often, this is a geographically isolated population with unique phenotypes; however, it remains biologically and behaviorally capable of interbreeding with other populations of the same species.<\/p>\n<p class=\"import-Normal\"><strong>Sympatric speciation<\/strong>: When a population splits into two or more separate species while remaining located together without a physical (or cultural) barrier.<\/p>\n<p class=\"import-Normal\"><strong>Synonymous mutation<\/strong>: A point mutation that does not change the resulting protein.<\/p>\n<p class=\"import-Normal\"><strong>Transposable elements<\/strong>: Fragments of DNA that can \u201cjump\u201d around in the genome.<\/p>\n<p class=\"import-Normal\"><strong>Transposon<\/strong>: Another term for \u201ctransposable element.\u201d<\/p>\n<p class=\"import-Normal\"><strong>Trisomies<\/strong>: Conditions in which three copies of the same chromosome end up in a cell, resulting from a nondisjunction event. Down syndrome, Edwards syndrome, and Patau syndrome are trisomies.<\/p>\n<p class=\"import-Normal\"><strong>Unbalanced translocations<\/strong>: Chromosomal translocations in which there is an unequal exchange of genetic material, resulting in duplication or loss of genes.<\/p>\n<p class=\"import-Normal\"><strong>UV crosslinking<\/strong>: A type of mutation in which adjacent thymine bases bind to one another in the presence of UV light.<\/p>\n<p class=\"import-Normal\"><strong>Viable offspring<\/strong>: Offspring that are healthy enough to survive to adulthood.<\/p>\n<p class=\"import-Normal\"><strong>Xeroderma pigmentosum<\/strong>: An autosomal recessive disease in which DNA repair mechanisms do not function correctly, resulting in a host of problems especially related to sun exposure, including severe sunburns, dry skin, heavy freckling, and other pigment changes.<\/p>\n<h2 class=\"import-Normal\">For Further Exploration<\/h2>\n<p>Explore Evolution on <a href=\"https:\/\/www.hhmi.org\/biointeractive\/evolution-collection\">HHMI\u2019s Biointeractive website<\/a>.<\/p>\n<p>Teaching Evolution through <a href=\"https:\/\/humanorigins.si.edu\/education\/teaching-evolution-through-human-examples\">Human Examples, Smithsonian Museum of Natural History websites<\/a>.<\/p>\n<h2 class=\"import-Normal\">References<\/h2>\n<p class=\"import-Normal\">Bloomfield, Gareth, David Traynor, Sophia P. Sander, Douwe M. Veltman, Justin A. Pachebat, and Robert R. Kay. 2015. \u201cNeurofibromin Controls Macropinocytosis and Phagocytosis in <em>Dictyostelium<\/em>.\u201d <em>eLife<\/em> 4:e04940.<\/p>\n<p class=\"import-Normal\">Chaix, Rapha\u00eblle, Chen Cao, and Peter Donnelly. 2008. \u201cIs Mate Choice in Humans MHC-Dependent?\u201d\u00a0<em>PLoS Genetics<\/em>\u00a04 (9): e1000184.<\/p>\n<p class=\"import-Normal\">Cook, Laurence\u00a0M. 2003. \"The Rise and Fall of the\u00a0<em>Carbonaria<\/em>\u00a0Form of the Peppered Moth.\" <em>The Quarterly Review of Biology<\/em> 78 (4): 399\u2013417.<\/p>\n<p class=\"import-Normal\">Cota, Bruno C\u00e9zar Lage, Jo\u00e3o Gabriel Marques Fonseca, Luiz Oswaldo Carneiro Rodrigues, Nilton Alves de Rezende, Pollyanna Barros Batista, Vincent Michael Riccardi, and Luciana Macedo de Resende. 2018. \u201cAmusia and Its Electrophysiological Correlates in Neurofibromatosis Type 1.\u201d <em>Arquivos de Neuro-Psiquiatria<\/em> 76 (5): 287\u2013295.<\/p>\n<p class=\"import-Normal\">D\u2019Asdia, Maria Cecilia, Isabella Torrente, Federica Consoli, Rosangela Ferese, Monia Magliozzi, Laura Bernardini, Valentina Guida, et al. 2013. \u201cNovel and Recurrent EVC and EVC2 Mutations in Ellis-van Creveld Syndrome and Weyers Acrofacial Dyostosis.\u201d <em>European Journal of Medical Genetics<\/em> 56 (2): 80\u201387.<\/p>\n<p class=\"import-Normal\">Dobzhansky, Theodosius. 1937. <em>Genetics and the Origin of Species. <\/em>Columbia University Biological Series. New York: Columbia University Press.<\/p>\n<p class=\"import-Normal\">Facon, Beno\u00eet, Laurent Crespin, Anne Loiseau, Eric Lombaert, Alexandra Magro, and Arnaud Estoup. 2011. \u201cCan Things Get Worse When an Invasive Species Hybridizes? The Harlequin Ladybird\u00a0<em>Harmonia axyridis<\/em>\u00a0in France as a Case Study.\u201d\u00a0<em>Evolutionary Applications<\/em> 4 (1): 71\u201388.<\/p>\n<p class=\"import-Normal\">Fisher, Ronald A. 1919. \"The Correlation between Relatives on the Supposition of Mendelian Inheritance.\" <em>Transactions of the Royal Society of Edinburgh<\/em> 52 (2): 399\u2013433.<\/p>\n<p class=\"import-Normal\">Ford, E. B. 1942.\u00a0<em>Genetics for Medical Students<\/em>. London: Methuen.<\/p>\n<p class=\"import-Normal\" style=\"background-color: #ffffff\">Ford, E. B.\u00a01949.\u00a0<em>Mendelism and Evolution<\/em>. London: Methuen.<\/p>\n<p class=\"import-Normal\">Grant, Bruce S. 1999. \u201cFine-tuning the Peppered Moth Paradigm.\u201d <em>Evolution<\/em> 53 (3): 980\u2013984.<\/p>\n<p class=\"import-Normal\">Haldane, J. B. S.\u00a01924.\u00a0\u201cA Mathematical Theory of Natural and Artificial Selection (Part 1).\u201d <em>Transactions of the Cambridge Philosophical Society<\/em>\u00a023 (2):19\u201341.<\/p>\n<p>Hoelzel, A. R., Gkafas, G. A., Kang, H., Sarigol, F., Le Boeuf, B., Costa, D. P., Beltran, R. S., Reiter, J., Robinson, P. W., McInerney, N., Seim, I., Sun, S., Fan, G., &amp; Li, S. (2024). Genomics of post-bottleneck recovery in the northern elephant seal. Nature Ecology &amp; Evolution, 8, 686\u2013694. https:\/\/doi.org\/10.1038\/s41559-024-02337-4<\/p>\n<p class=\"import-Normal\">Imperato-McGinley, J., and Y.-S. Zhu. 2002. \u201cAndrogens and Male Physiology: The Syndrome of 5 Alpha-Reductase-2 Deficiency.\u201d\u00a0<em>Molecular and Cellular Endocrinology <\/em>198 (1-2): 51\u201359.<\/p>\n<p class=\"import-Normal\">Jablonski, David, and W. G. Chaloner. 1994. \"Extinctions in the Fossil Record.\u201d\u00a0<em>Philosophical Transactions of the Royal Society of London\u00a0B: Biological Sciences<\/em>\u00a0344 (1307): 11\u201317.<\/p>\n<p class=\"import-Normal\">Livi-Bacci, Massimo. 2006. \u201cThe Depopulation of Hispanic America after the Conquest.\u201d <em>Population Development and Review<\/em> 32 (2): 199\u2013232.<\/p>\n<p class=\"import-Normal\">Lombaert, Eric, Thomas Guillemaud, Jean-Marie Cornuet, Thibaut Malausa, Beno\u00eet Facon, and Arnaud Estoup. 2010. \"Bridgehead Effect in the Worldwide Invasion of the Biocontrol Harlequin Ladybird.\u201d <em>PLoS ONE<\/em> 5 (3): e9743.<\/p>\n<p class=\"import-Normal\">Martins, Aline Stangherlin, Ann Kristine Jansen, Luiz Oswaldo Carneiro Rodrigues, Camila Maria Matos, Marcio Leandro Ribeiro Souza, Juliana Ferreira de Souza, Maria de F\u00e1tima Haueisen Sander Diniz, et al. 2016. \u201cLower Fasting Blood Glucose in Neurofibromatosis Type 1.\u201d <em>Endocrine Connections<\/em> 5 (1): 28\u201333.<\/p>\n<p class=\"import-Normal\">Pickering, Gary, James Lin, Roland Riesen, Andrew Reynolds, Ian Brindle, and George Soleas. 2004.\u00a0\"Influence of\u00a0<em>Harmonia axyridis<\/em>\u00a0on the Sensory Properties of White and Red Wine.\"\u00a0<em>American Journal of Enology and Viticulture<\/em>\u00a055 (2): 153\u2013159.<\/p>\n<p class=\"import-Normal\">Repunte-Canonigo Vez, Melissa A. Herman, Tomoya Kawamura, Henry R. Kranzler, Richard Sherva, Joel Gelernter, Lindsay A. Farrer, Marisa Roberto, and Pietro Paolo Sanna. 2015. \u201cNF1 Regulates Alcohol Dependence-Associated Excessive Drinking and Gamma-Aminobutyric Acid Release in the Central Amygdala in Mice and Is Associated with Alcohol Dependence in Humans.\u201d <em>Biological Psychiatry<\/em> 77 (10): 870\u2013879.<\/p>\n<p class=\"import-Normal\">Riccardi, Vincent M. 1992. <em>Neurofibromatosis: Phenotype, Natural History, and Pathogenesis.<\/em> Baltimore: Johns Hopkins University Press.<\/p>\n<p class=\"import-Normal\">Sanford, Malcolm T. 2006.\u00a0\"The Africanized Honey Bee in the Americas: A Biological Revolution with Human Cultural Implications, Part V\u2014Conclusion.\"\u00a0<em>American Bee Journal <\/em>146 (7): 597\u2013599.<\/p>\n<p class=\"import-Normal\">Sanna, Pietro Paolo, Cindy Simpson, Robert Lutjens, and George Koob. 2002. \u201cERK Regulation in Chronic Ethanol Exposure and Withdrawal.\u201d <em>Brain Research<\/em> 948 (1\u20132): 186\u2013191.<\/p>\n<p>Weber, DianaS., Stewart, B. S., Garza, J. Carlos., &amp; Lehman, N. (2000). An empirical genetic assessment of the severity of the northern elephant seal population bottleneck. Current Biology, 10(20), 1287\u20131290. https:\/\/doi.org\/10.1016\/s0960-9822(00)00759-4<\/p>\n<p class=\"import-Normal\">World Health Organization. 1996. \u201cControl of Hereditary Disorders: Report of WHO Scientific meeting (1996).\u201d WHO Technical Reports 865. Geneva: World Health Organization.<\/p>\n<p class=\"import-Normal\">World Health Organization. 2017. \u201cGlobal Priority List of Antibiotic-Resistant Bacteria to Guide Research, Discovery, and Development of New Antibiotics.\u201d Global Priority Pathogens List, February 27. Geneva: World Health Organization. https:\/\/www.who.int\/medicines\/publications\/WHO-PPL-Short_Summary_25Feb-ET_NM_WHO.pdf.<\/p>\n<p class=\"import-Normal\">Wright, Sewall. 1932. \"The Roles of Mutation, Inbreeding, Crossbreeding, and Selection in Evolution.\" <em>Proceedings of the Sixth International Congress on Genetics<\/em> 1 (6): 356\u2013366.<\/p>\n<h2 class=\"import-Normal\">Acknowledgment<strong><br \/>\n<\/strong><\/h2>\n<p class=\"import-Normal\">Many thanks to Dr. Vincent M. Riccardi for sharing his vast knowledge of neurofibromatosis and for encouraging me to explore it from an anthropological perspective.<\/p>\n<\/div>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_280_1708\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_280_1708\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":94,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-280","chapter","type-chapter","status-publish","hentry"],"part":20,"_links":{"self":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapters\/280","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/wp\/v2\/users\/94"}],"version-history":[{"count":10,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapters\/280\/revisions"}],"predecessor-version":[{"id":804,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapters\/280\/revisions\/804"}],"part":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/parts\/20"}],"metadata":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapters\/280\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/wp\/v2\/media?parent=280"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/pressbooks\/v2\/chapter-type?post=280"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/wp\/v2\/contributor?post=280"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/opentextbooks.concordia.ca\/explorationsversiontwo\/wp-json\/wp\/v2\/license?post=280"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}