PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Earliest humans walked bipedallyBut had small brainsWhy did brains not get large until later?First big jump in brain size (cranial capacity)was with the beginning of the genus Homo,but there is a small increase among AustralopithecinesFor comparative purposes, brain size in ml:Modern human 1150-1750 (x=1325)Homo habilis 500-800 (x=680) (20-50% bigger)A. afarensis 380-500 (x=440) (10% bigger)Modern chimp 285-500 (x=390)Radiator TheoryThe idea that brains could not expand untila new pattern of blood flow developed tokeep the brain from getting too hotdespite standing uprightIn the fossil recordfind two different patterns of blood drainagefrom the craniumGracile Australopithecine and Homo lineage:like ours today – two alternate drainsRobust (Paranthropus) lineage is different:only one major drainThe Radiator Theoryapplies to Australopithecus fossils:from that point on, we see thedouble blood drainage systemBut a second theory addresses the hugejump in cranial capacity we see withHomoExpensive Tissue HypothesisIs associated with both a change in therib cage shape first seen in Homo erectusAND a change in dietWe’ll talk more about this hypothesisnext week when we learn aboutHomo erectusSo when did humans first develop language?Are there any physical clues that could tell us?Are there any cultural clues: at what point MUSTthey have had language to do the things they did?When did language develop and what evidencecould we see in the fossil record?1. Does vocal apparatus at basicranium allow speech? Basicranium: bones at base of skull2. Do we see modern brain structure and organization? Left hemisphere controls language and ability to use symbols.3. At what point did hominids have something to communicate about that would require language?1. Basicranium anatomy: modern human’s allows greater range of sounds because is flexed.Australopithecines do not have this anatomy yet.But we can’t yet reconstruct early Homo vocal tract.Modernchimpmodernhuman(Feder & Park 2001:253)2. Endocasts show asymmetrical brains and language-associated areas in all Homo and Australopithecus, as well as modern chimpanzees (not all exactly alike).3. It could be that it is not until Homo that a social need developed for
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