ANTH1102Lecture 13Outline of Last Lecture I. Allen and Bergman’s Rules continued (adaptation)II. Why Anthropologists Study Non-Human PrimatesA. ReasonsB. Origins of the Human SpeciesC. Tendencies (of Primates)Outline of Current LectureI. BipedalismA. HistoryB. How Do We Know They Were BipedalC. Hominin SpeciesD. Why bipedal?Current LectureHistory- Hominids: primates; Hominins: human lineage - Many hominin fossils have been found in Africa.> Taphonomy (study of how decaying organisms became fossilized)- possible reasons: scavengers, weather, floods, solarization, bioturbation, geologic forces, diagenesis- Uniformitarianism, paleoecology, fossil associations, and modern proxies can alllead to inferences about how the hominins lived.How do we know they were bipedal?- anatomy- foramen magnum (hole in skull where spine connects), curved vertebral column, pelvis, femur, knees, the foot components- orthograde (upright walking- center of mass directly above hips) and to what effect on efficiency, speed, swiftness, flexibility, vision, solar exposure vs. facultative bipedalism (not necessary to walk upright, only sometimes)> The foramen magnum is posterior in primates because the vertebral column is at an angle, while it is less far back in humans whose vertebral column is vertical.- Great ape quadruped- “C” curved spinal column; hominin bipeds- “S” curved spinal column (sacral vertebra more robust- I.e. thicker bones for more support)- Hominin pelvis is wider and shorter and the birth canal can accommodate larger skulls, angle of femur socket is different (hominins walk with legs closer together than primates do), knees are more robust for inward support and ankles less flexible (no need to climb trees as much as primates have in the past)- Laetoli tracks: proved bipedalism and non-opposable hallux (big toe) and humanlike arch-> they were obligatory bipeds…(opposable big toe=abducted, in line big toe= adducted)Hominin Species- The oldest acknowledged hominins are the sahelanthropus tchadensis, 6.5mya.- Ardipithecus ramidus kadabba, 4.4mya, had an opposable hallux though the femur and pelvis were bipedal like; also they were arboreal with long arms compared to the legs.- Australopithecus afarensis (Lucy), 3.6-2.9mya was very small (about 3 ft), very similar to modern humans though.- Homo erectus, 1.8mya-100,000ya were probably the most successful hominins (went unchanged for a very long time).Why bipedal?- hypotheses: savannah, vision (ability to see predators), feeding, arboreal bipedality (most popular), sex-and-reproduction, climate, technology, efficiency> not one is completely true; some may be true
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