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Integrated different disciplines to study human evolution

Integrated different disciplines to study human evolution. need to use multiple approaches anatomy molecular genetics study of fossils-taphonomy past environments comparisons with modern & fossil primates examination of behaviors among living people. Anatomy. study of modern skeletons

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Integrated different disciplines to study human evolution

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  1. Integrated different disciplines to study human evolution • need to use multiple approaches • anatomy • molecular genetics • study of fossils-taphonomy • past environments • comparisons with modern & fossil primates • examination of behaviors among living people

  2. Anatomy • study of modern skeletons • effects of activity • growth • disease • age • diet • environmental effects • compare with fossils

  3. Molecular Evolution • can help us understand divergence in new ways • timing • geographical spread • traits that are linked in evolution

  4. Fossils & Taphonomy • modification of remains • animal damage • weathering • crushing & distortion through burial • chemical modification

  5. Past Environments plant remains geologic setting invertebrate remains large fauna

  6. Living & Fossil Primates • diet • locomotion • behaviors • anatomy • sociality • evolution tarsier Proconsul africanus Kenya,14-23 mya baboons

  7. dietary decisions • sociality • sexual strategies • growth & development • population dynamics Living Humans

  8. What were the ancestors like?What does it mean to be human? Homo habilisKNM ER-1813 Koobi Fora, Kenya1.9 mya

  9. Primates have grasping hands for locomotion and feeding baboon pygmy marmoset

  10. Primates have large, forward facing eyes for stereo vision tamarin tarsier ring tail lemur slender loris chimpanzee male

  11. tarsier, Tarsius sp., small prosimian, Indonesia, vertical clinger & leaper

  12. Lemurs • Madagascar • terrestrial locomotion • arboreal clingers & leapers • climbers • social group living

  13. Vertical leaping • crouched and clinging to a limb • thigh muscles provide the force to produce a leap • arms used mostly for balance stabilization • land feet first Drawings by Luci Betti

  14. sifaka, lemur

  15. Baboons terrestrial locomotion

  16. New World Monkeys • arboreal • suspensory • above limb walking • mostly group living capuchin monkey

  17. Gibbons • Asia • brachiation • underbranch suspension

  18. Orangutan • Sumatra & Borneo • slow • solitary • suspensory locomotion

  19. Gorilla • Central Africa • group living • terrestrial knuckle-walker

  20. Chimpanzees & Bonobos • Central Africa • group living • highly social • terrestrial & arboreal adaptations • last great ape line that the hominin lineage diverged from ~10-7 mya chimpanzee, Pan troglodytes bonobo, Pan paniscus

  21. chimpanzee, Pan troglodytes, west and central Africa, forest knuckle walker-terrestrial locomotion and climbing

  22. Adaptive Radiations of Primates • Paleocene~60 mya-earliest possible primates • Eocene mya ~56-35 mya • Late Oligocene ~30-22 • Miocene ~22-11 mya

  23. tree shrews resemble primitive primates • different ear bones • have claws • non-grasping hands • eye orbits not closed

  24. Ida” 47 mya adapiform, near Frankfurt, Germanylemur-like prosimian ancestor

  25. Aegyptopithecus zeuxisEgyptian Fayum, 29 mya, Miocene

  26. Proconsul africanusRusinga Island, Kenya,14-23 mya, Miocene

  27. Sivapithecus indicus Potwar Plateau, Pakistan, 8.5-12.5 mya, Late Miocene, orangutan ancestor

  28. Sivapithecines = ancestors of the Orangutan lineage

  29. Sahelanthropus tchadensisChad, 6-7 mya

  30. Sociality

  31. Brain size Brain size % fruit in diet Group size Findings from the “ecological” and “social” hypotheses Mountain gorilla Points reflect individual species: both are upheld

  32. Neocortex and group size Look at relationship of “social part of brain”-neocortex- with respect to group size Data tend to support “social” hypothesis, since this relationship doesn’t hold for ecological factors

  33. Human social organization Human social organization is a mosaic of traits that have deep roots. Different traits arose at different times in different circumstances

  34. Grooming

  35. Male Aggression

  36. primate sexual dimorphism associated with distinct feeding, mating, and sociality gorilla female gorilla male

  37. Tamarin reproductive biology Insights into patterns of male care-giving and male fitness. Tamarin groups 1-3 adult males and 1-3 adult females. After mating with all group males, the alpha female gives birth to dizygotic twins, other females often don’t reproduce. Each offspring weighs 8% of mom’s weight and grows rapidly (in humans, the equivalent to giving birth to two 9lbs infants) The alpha female can give birth to two sets of twins in a year

  38. 2.5 2 1.5 1 .5 0 males Ave. number of surviving offspring females 0 1 2 3 4 5 6 Number of adult males/females Offspring survival depends on male care in tamarins In one study group, males did 73% of all infant carrying. Adult males will also provision infants with food. Males will provision infants/juveniles for 50% of their growth period (long, relative to other primates)

  39. Tamarin reproductive biology Main point: male investment in offspring is a fact of tamarin male behavior; it is a function of local ecology, life history patterns, and reproductive options. Tamarin males, like human males, have high potential reproductive rates, but the evolved tamarin mating system does not let males actualize their reproductive potential. Instead, they share matings/reproduction with other males.

  40. Brain • not just an increase in size • differences in brain organization • cognition • thought • emotions • brain is a costly tissue • affects dietary needs • growth & development • birth

  41. Primates: Unusually large brain relative to body size. Monkeys and apes: Very large brain when compared to other mammals Humans: Carry this pattern to greater extreme Large brains are expensive to maintain: Brains ~2% of body weight, consume ~20% metabolic energy We wouldn’t expect natural selection to maintain this costly feature unless it was adaptive.

  42. Neocortex • very thick in humans and non-human primates • 30-40% brain volume in non-primate mammals • 50% brain volume in prosimians • 80% brain volume in humans

  43. Interspecific comparisons

  44. Encephalization Quotient (EQ): an to compare brain size across sepcies • EQ the ratio of brain size to body mass based on interspecific comparisons. “Encephalization” refers to the degree of “excess” brain mass relative to body size. • EQ’s take into account body size, since-obviously, an elephant’s brain will weigh more than a mouse’s brain on an absolute scale. • However, taking the ratio of brain size to body mass allows us to compare brains in diverse taxa.

  45. EQ in humans larger than expected • the line shows expected brain size for a give body size • points above the line indicates a larger than expected brain size for a given body size

  46. Encephalization Quotient (EQ): ratio of brain size to body mass based on a linear regression of interspecific data for primates. EQs for various catarrhine taxa: baboon 1.1 gorilla (male) 2.1 chimpanzee 2.3 australopithecines 2.5 H. habilis 3.1 H. erectus 3.5 H. sapiens 7.5

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