1323442158_CHAPTER_20_SPR

1323442158_CHAPTER_20_SPR - EVOLUTION/LECTURE1 Evolution...

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EVOLUTION/LECTURE1 file:///E|/CH20-HUMAN-EVOLU-SPRING-2008/CHAPTER%2020_SPR_2008.HTML[12/8/2011 2:59:50 PM] Evolution ( PCB 4674 ). Chapter 20. Human evolution Main topics of lecture: I: Relationships among humans and the extant apes: 1.- Humans belong to the same clade as the apes 2.- Humans, gorillas, chimpanzees, and bonobos: Morphological evidence 3.- Humans, gorillas, chimpanzees, and bonobos: Molecular evidence II: The recent ancestry of humans: 4.- The fossil evidence for early humans 5.- Interpreting the fossil evidence and some answers III: The origin of the species Homo sapiens : 6.- Controversies over the origin of modern humans 7.- African replacement versus multiregional evolution: Molecular evidence I: Relationships among humans and the extant apes: 1.- Humans belong to the same clade as the apes 1.1.- Humans ( Homo sapiens ) belong to the primate taxon infraorder Catarrhini , which includes the Old World monkeys (such as the baboons and macaques), apes and the Hominoidea (Fig. 16.1). The Hominoidea, also referred to as the hominoids, include the gibbons ( Hylobates ) of southeast Asia and the Hominidae . The Hominidae, or hominids , include the orangutan ( Pongo pygmaeus ), also of southeast Asia, and three African species: the gorilla ( Gorilla gorilla ), the common chimpanzee ( Pan troglodytes ), and the pygmy chimpanzee ( Pan paniscus ). Gibbons, orangutans, gorillas, and chimpanzees are referred to informally as apes . Orangutans, gorillas, and chimpanzees are referred to as great apes . The infraorder Catarrhini belongs to the order Primates. Figure 16.1.: Phylogeny of the Catarrhini. The evolutionary relationships among the gorilla, the two chimpanzees, and humans have been the subject of considerable dispute
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EVOLUTION/LECTURE1 file:///E|/CH20-HUMAN-EVOLU-SPRING-2008/CHAPTER%2020_SPR_2008.HTML[12/8/2011 2:59:50 PM]
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EVOLUTION/LECTURE1 file:///E|/CH20-HUMAN-EVOLU-SPRING-2008/CHAPTER%2020_SPR_2008.HTML[12/8/2011 2:59:50 PM] 1.2.- Scientists universally agree that humans belong with the apes in the Hominoidea. Humans share with the apes numerous derived characteristics ( synapomorphies ). These evolutionary innovations distinguish the hominoids from the rest of the Catarrhini and indicate that the hominoids are descended from a common ancestor. The shared derived traits of the hominoids include relatively large brains, the absence of tail, a more erect posture, greater flexibility of the hips and ankles, increased flexibility of the wrist and thumb, and changes in the structure and use of the arm and shoulder. In addition to this morphological evidence, the molecular analyses also unequivocally demonstrate that humans are hominoids. 1.3.- The phylogenetic reconstruction showed in Fig. 16.1 places humans with the great apes in the Hominidae. Furthermore, it places humans with the African great apes in the Homininae . The reconstruction was first proposed by Thomas Henry Huxley in 1863. Scientists in all fields have accepted the tree in Fig. 16.1. Cladistic
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1323442158_CHAPTER_20_SPR - EVOLUTION/LECTURE1 Evolution...

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