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a201-11f-25-HomoButNotUs

a201-11f-25-HomoButNotUs - Introduction to Biological...

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Introduction to Biological Anthropology: Notes 25 Homo but not quite us Copyright Bruce Owen 2011 - As we saw last time, the first species of the genus Homo appeared about 1.8 mya - different from the other, earlier hominins in that it had - “slow, long, large” life history strategy - slower juvenile development - longer lifespan - larger body size - reduced sexual dimorphism - suggesting reduced male-male competition - maybe long-term pair bonding - Boyd and Silk argued that this could have been due to the complex extractive foraging strategy adopted by the Oldowan toolmakers starting around 3.4 mya - (they say 2.5 mya, but the recently discovered cutmarks at Dikka push it back) - whatever species they were - This first species of the genus Homo was Homo ergaster - 1.8 – 0.6 mya - appeared right at the beginning of the Pleistocene, a period of cold and variable climate - probably hunted game (more on this later) - probably controlled fire (more on this later) - began to make more well-planned, intentional stone tools (Mode 2 tools, called Acheulean style; more on this later) - but initially did NOT have a much larger brain relative to body size than earlier hominins - Some features of Homo ergaster - Still had some ancestral traits (inherited from possibly australopithecine ancestors) - low forehead - cranium pinches in behind the eyes - New, derived traits that resemble humans - more vertical face - smaller, more lightly built face - smaller teeth overall - indicates less emphasis on plant foods that require grinding, like seeds - and smaller molars relative to other teeth - shifting from back-tooth grinding towards more tearing and pulling with front teeth - which might indicate eating more meat (maybe) - projecting, human-like nose - probably a side effect of the teeth and jaws developing less - while the nasal bones and tissues remained about the same - New, derived traits that do not resemble humans - occipital torus (also called nuchal torus) - thickening of bone in an arc around the lower back of the cranium
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Intro to Biological Anthro F 2011 / Owen: Homo but not quite us p. 2 - strengthens the back of the cranium where major neck muscles attach - gives the lower back of the cranium a “pointed” look from the side - were strong neck muscles needed to pull on something held in the mouth? - as in eating meat? - huge browridges - apparently strengthen face - related to pulling or tearing with front teeth? - as in eating meat? - larger brain in absolute size: early H. ergaster around 800 cc - compare to most australopithecines, in the 450 cc range - compare to the one brainier australopithecine, A. rudolfensis , around 775 cc - but body size is also larger than earlier hominins, like modern humans - so relative to body size, H. ergaster brain is not much larger than most australopithecines - maybe even smaller than the brainy A. rudolfensis , relative to body size - But H. ergaster brains got larger over time, eventually reaching around 1000 cc - Hint that H. ergaster may not have been able to speak as modern humans do - modern humans have a larger diameter opening in the cervical (neck) and thoracic (upper
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