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Major Primate Groups

5 mya. 6 mya. 12 mya. 25 mya. Estimated Divergence Times. 38 mya. Hasegawa et al. 1987. Major Primate Groups. Family Hominidae. Old World Monkeys. Orangutan. Chimp. Human. Tarsiiformes. Gorilla. Gibbons. New World Monkeys. Lemurs. What Traits Do Humans and Apes Share?.

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Major Primate Groups

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  1. 5 mya 6 mya 12 mya 25 mya Estimated Divergence Times 38 mya Hasegawa et al. 1987 Major Primate Groups Family Hominidae Old World Monkeys Orangutan Chimp Human Tarsiiformes Gorilla Gibbons New World Monkeys Lemurs

  2. What Traits Do Humans and Apes Share? • Larger Brain • Absence of a tail • More erect posture • Greater flexibility of hips, ankles, wrist, thumb • DNA sequence similarity

  3. Gorilla Human Chimpanzee Horai et al (1995) Proc. Nat Acad Sci. 92:532-536. Mito DNA (complete sequences) Kim and Takenaka (1996) A. J. Phys. Anth. 100:301-309 Y-chromosome DNA Ruvolo (1997) Mol Biol Evol 10:1115-1135. Examined 14 different DNA data sets Satta et al (2000) Mol. Phyl. Evol 14:259-275. Autosomal DNA (45 genes, 47,000 bp of DNA)

  4. Common Ancestor of Chimp/Human • Knuckle-walker • Broad-fruit based diet • May have hunted • May have used tools • May have had complex social relationships: • (e.g.warfare, cannabalism, sharing, • teaching, compassion)

  5. Our Understanding of Human Evolution is Primarily Based on Fossils Gracile Australopithecines

  6. Fossil Evidence Indicates Two Primary Hominid Groups Chimp / Human Split

  7. Australopithecus/Paranthropus • 4.1 mya to 1.2 mya • Bipedal • Foramen magnum faces down • 3.6 my footprints found in volcanic ash near afarensis fossil • Large projecting face, small brain case (400 cm3 ) • Small in stature (3’7’’ - 4’11’’ ft) • Two distinct lineages (gracile and robust) • May have developed tools

  8. Homo is thought to have evolved from A. afarensis Chimp / Human Split

  9. Homo • 1.9 mya to present • Larger braincases (cro-magnon: 1600 cm3) than australopithecines and smaller face • Smaller jaws and teeth • Much taller than australopithecines • Development of tools, culture, and language

  10. Trends in Homo Evolution • Increase in brain volume • Increase in size • Skull evolution : vertical face, smaller jaw, round forehead • Bipedalism • Tool development • Cultural development

  11. Slight Increase In Body Size Much Greater Increase In Brain Volume

  12. Braincase Volume and Body Mass

  13. Early Tools

  14. Evidence that P. robustus used tools These species are associated with manufactured stone tools. Paranthropus robustus Susman, 1994

  15. Is Language a Recently Evolved Trait Unique to Homo sapiens? Earliest cave paintings are 32,000 yrs old. Neural circuits of the brain associated with language (Broca’s area and Wernicke’s area) are enlarged in H. habilis. The neandertal hyoid of the larynx is exactly like our hyoid.

  16. Hyoid Bone Neandertal Larynx Hyoid Bone Chimp Larynx

  17. Summary of Hominid Evolution Since the Chimp/Human Common Ancestor • Frequent speciation produced a diversity • of species • As many as 5 different species may have • coexisted at one time • We are the lone survivors of an otherwise • extinct radiation of bipedal African hominids

  18. What is the Origin of Modern Human Populations? • Multiregional Hypothesis • Homo sapiens evolved from an ancient stock of Homo erectus that originated in Africa (~ 1-1.8 mya) • Out of Africa Hypothesis • Homo sapiens evolved from a relatively recent stock of archaic sapiens that originated in Africa (~ 100-200,000 ya)

  19. Chimp / Human Split

  20. How Can We Test These Hypotheses With Molecular Data? • Multiregional Hypothesis • Predicts that Homo sapien “eve” existed more than 1 mya. • Out of Africa Hypothesis • Predicts that Homo sapien “eve” existed ~ 200,000 yr ago.

  21. Molecular Clock Estimate of Divergence Time of Modern Humans GeneEstimateReference mt DNA 166-249,000 Vigilant et al., 1991 mt DNA 129-536,000 Ruvolo et al., 1993 nuclear DNA 75-287,000 Bowcock et al., 1994 mt DNA 125-161,000 Horai et al., 1995 nuclear DNA 102-450,000 Tishkoff et al., 1996

  22. Overall, Out of Africa is Supported by the Majority of the Evidence “In each great region of the world the living mammals are closely related to the extinct species of the same region. It is , therefore, probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; And as these two species are now man’s nearest allies, It is somewhat more probable that our early progenitors lived on the African continent than elsewhere.” Charles Darwin The Descent of Man, 1871

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