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Biology-Lecture 4 Chapter 8-Early Hominins Oct 3 2008

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University of Toronto St. George
Marcel Danesi

Reading Notes 10-03-08 Chapter 8: Early Hominins O Australopithecus: genus of Pliocene and Pleistocene hominins O Homo: genus to which modern human beings and their ancestors belong Trends in Hominin Evolution O Development of bipedal locomotion (walking on 2 legs) O Expansion of brain, modification of the female pelvis (allow bigger brained babies to be born), reduction of face, teeth, jaw O Extended period of infantchild dependency, increased reliance on meat Bipedalism O Slowquickly?- sparse fossil records O Miocene anthropoids- capable of assuming upright position O Bipedal- Africa (16 -11 MYA)- changing environment: tropical forests-> open country O Open country favored ground living O Bipedalism: adaptive response to life amid the tall grasses of savannahs (spot predators) O Better dispersion of body heat O Allowing hands to be free while legs moving (carrying food etc) O Efficiently harvest small seeds and nuts because both hands could be used to pick up food and move it directly to the mouth O Use and make toolsweapons that they could carry with them as they moved about (hunting- teethjaw not strong enough) O (-)= harder to overcome gravity to supply blood to brain, weight of body above pelvis and lower limbs- puts greater stress on hips, lower back, knees, feet, (even greater for pregnantnursing females) O Changes in ape skeleton O Foramen Magnum: the hole in the base of the skull through which the spinal cord passes en route to the brain O Pelvis is bowl shaped, has different set of muscles attach to femurs (move legs forward), support internal organs, lowers the bodys centre of gravity O Legs- angle inward toward one another (move legs forwardmaintain centre of gravity) O Feet- enlarged group ankle bones forming robust heel that can withstand the substantial forces placed on them as a result of habitual Bipedalism O Also have arch (absorbs locomotion force) Expansion of the Brain st O Bipedalism evolved 1 -> development of brain O Homo Habilis: early species belonging to our genus, Homo, with cranial capacities averaging about 630-640 cc, about 50% of the brain capacity of modern humans (2 MYA) O Homo Erectus: the first hominin species to be widely distributed in the Old World. The earliest finds are possible 1.8 MYO. The brain (averaging 895-1040 cc) was larger than that found in any smaller than the average brain of a modern human O Stone tool making-> favored bigger-brained individuals because the had motor and conceptual skills that enabled them to be better tool makers O Expansion of brain-> hunting, increase lifespan, and language Reduction of the Face, Teeth, and Jaw O After 2 million years O Diet- plants, seeds roots, tubers O Staring to eat foods easier to chew (not needing such largestrong features)->
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