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The Story of Human Evolution

The Story of Human Evolution. From Primates to Homo sapiens sapiens. The Myth of the Biggest and Bestest. “survival of the fittest” Our cultural problem Stephen Jay Gould

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The Story of Human Evolution

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  1. The Story of Human Evolution From Primates to Homo sapiens sapiens

  2. The Myth of the Biggest and Bestest • “survival of the fittest” • Our cultural problem • Stephen Jay Gould • history of biological life = “proliferation of enormously varied designs subsequently restricted to a few highly successful, but imperfect, forms” • “Our world is not an optimal place fine-tuned by omnipotent forces of selection. It is a quirky mass of imperfections, working well enough (often admirably); a jury-rigged set of adaptations, built of curious parts made available by past histories in different contexts.”

  3. Considering Evolution • Natural Selection: • an evolutionary process through which factors in the environment exert pressure that favors some individuals over others to reproduce the nextgeneration of the group • this pressure acts on phenotype (genes plus environment), not genotype (DNA, genetic makeup)

  4. Never exact match between phenotype • and genotype • Never exact fit between organism and • environment: dynamism • Biological plasticity of individuals

  5. Note: there are prosimians (eg lemurs), new world monkeys (eg spider monkey, Old world monkeys (eg baboons), and apes. Apes include gibbons, orangutans, chimps, bonobos, gorillas and humans. 99% of human DNA shared with chimps (study in Nature, 8.31.2005) Fig 8-2

  6. Primate Tendencies • Grasping and opposable thumbs • Smell  sight • mouth  hand • brain complexity increases • parental investment increases • Sociality increases Snarling mandrill

  7. Gorilla family gibbon humans chimp

  8. Primate Social Behavior • Wide range of social behaviors and types of social organization for different species—a few examples follow • Male led (chimps), female led (bonobos), • Savanna baboons—highly complex multi male and female troops • Only ape that is monogamous—gibbon • Apes that display wide range of sexual behavior—bonobos

  9. Overview of Hominid Evolution • Australopithecines (Lucy) 5-2 million years ago (mya) • Gracile • Robust • Homo habilis (3-2 mya) • Homo erectus (1.5 – 0.4 mya, or ?12,000ya) • Homo sapiens (.02 mya, 200k-present) • Homo sapiens neanderthalensis 60k • Homo sapiens sapiens (dif places different times) 200,000k

  10. Key Ideas • Feedback and inadvertency • Bipedalism • Brain Size/complexity • Tools, Language and Culture • Shifts in lifestyles/diets • Types of evolutionary change • Graduated • Punctuated Equilibrium

  11. Chimp Skeleton Human skeleton Fig 9-5

  12. Characteristics of Australopithecines • General Characteristics • Skeleton: Bipedal, not fully upright • Brain only slightly bigger than a chimp’s. • Smaller canines than a chimp, bigger molars • Hands: precision and power grip. • Likely savanna adaptation—likely vegetarian • Robustus has extreme savanna adaptation • Recent debate re: degree of bipedality, habitat type

  13. The skeleton of Lucy, notice the bipedality along with a relatively small cranium and chimp-like skull

  14. Australopithecus sites in Africa Fig 9-8

  15. On Bipedalism: Australopithecines take steps… • Disadvantages? • visible to predators • exposed underbelly • slow • Advantages? • Man the hunter? (NO!) • Woman the food carrier • Infant carry Artist’s rendering of A. africanus (interesting way in which racial ideas intervene)

  16. Why Be Bipedal? • Advantages, con’d • Efficient food procurement? • See farther? • Efficient long distance travel? • Cool brain? • All of the above? Artist’s rendering of A. africanus

  17. Effect of Bipedality: inadvertency in human evolution, 2 examples • 1. Hands are free • tool use • increasing tool use leads to increasing brain size and complexity • 2. the birth canal problem and its consequence • (evolution at work)

  18. Pelvis structure of Humans and Chimps Fig 9-6

  19. From Australopithecus to Homo: moving towards culture • Homo habilis (the handy man!)—(3-2 mya) • Brain • larger: 650 cm2 • area of skull indicates language • Body • more gracile

  20. Robust and Habilis Hung Out • Robust australopithecines (A. boisei) and H. habilis co-existed for at least 1/2 million years • What happened? Why did Australopithecines die out? • Competitive exclusion? • Niche divergence? (natural selection is environment specific)

  21. Homo Erectus • Lived 1.5 to .4 mya • 1 mya as single spp. • Example of punctuated equilibrium • Significant increase in brain size: 850-1200 • Fully erect/bipedal

  22. Homo Erectus Lifestyle, con’d • First use of fire • cook • heat • protection against predators • thaw out carcasses • Evidence of “culture” or symbolic activity • complexity of tools • cooperative hunting • red ochre

  23. Illustration of an Erectus cooperative elephant hunt

  24. Homo Erectus lifestyle, con’d • Migration out of Africa, first time in H. history

  25. Modern Humans, Early Homo sapiens sapiens • Timing of first evidence • Africa: more than 100,000 ya • Asia: 60,000 ya • Europe: 35,000 ya • Australia: 40,000 ya • Americas: 20,000 ya

  26. Early Modern H. s. s. • Cultural changes • Art (Cro Magnon) • tools • standardization • distinct sets for distinct areas indicating cultural diversity

  27. Neanderthals • Debate over where they belong in evolutionary story • The “cave man” …with a large brain • Robust skeletons • Latest research

  28. Recent Finding from Indonesia • 2004: Tiny Homo floresiensis, 3 feet tall, resembling H. erectus in some ways, but found with evidence of highly developed culture, boats, etc • Endemic island dwarfing (happens to a lot of other large mammals on islands) • Small brain, lots of smartness… • Co-habited earth with modern humans—these finds are from 12-18 k years ago • Cultural groups in the area have stories/legends about “small people” • Most recent debates: some researchers argue that these are just small modern humans

  29. Theories of the Origins of Modern Humans • Two competing theories: • Multiregional • Replacement/Out of Africa • Multiregional/Local Continuity Theory • evidence • apparently intermediate fossil forms between H. erectus and modern humans in each location (Africa, Asia, Europe)

  30. Theories of the Origins of Modern Humans, con’d • Replacement/Out of Africa-Mitochondrial Eve Theory • evidence • earliest H. sapiens sapiens found in Africa • Mitochondrial and nuclear DNA • all humans closely related, genes diverged from single recent African origin, at about 100 kya • Neanderthal mtDNA is not more similar to European than any other

  31. The Most Logical Theory: A Mix of the two • Independent evolution unlikely 3x • Interbreeding/gene flow likely, migration and movement all along • The human thing • migration • interbreeding • Implications for understanding race

  32. Questions to ask about your skulls • What species is it? • When did it live? • What are its key skeletal and other (?culture, etc) features • Why is it significant? • Where does it fit on evolutionary tree leading to Homo sapiens sapiens

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