a201-11f-23-WorldFullOfPlioPleistoceneHominins -...

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Introduction to Biological Anthropology: Notes 23 A world full of Plio-pleistocene hominins Copyright Bruce Owen 2011 - Let’s look at the next chunk of time: 3.0 – 1.0 mya - often called the Plio-pleistocene (end of the Pliocene, beginning of the Pleistocene) - numerous species of bipedal apes (hominins), more varied adaptations - in some times and places, 2 or 3 hominins lived in the same environment at the same time - Australopithecus species - presumably descendents of the earlier A. afarensis and maybe others - at least 5 species during this period - up to 2, probably 3 at the same time - called australopithecines in general - Paranthropus species - at least 3 species during this period - up to 2 at the same time - called paranthropines in general - plus possible descendents of Kenyanthropus , although no fossils have been found yet - plus, halfway through this period (1.8 mya), the first species of our genus: Homo - we’ll look at those later - All the Plio-pleistocene hominins (3.0 to 1.0 mya) shared certain basic features: - all bipedal - all had similar small bodies, only slightly larger than Lucy ( A. afarensis ) - all had chimp-size brains (chimps have a cranial capacity of about 300-400 cc; gorillas 540 cc) - except one late australopithecine ( A. rudolfensis ) that evolved a larger brain - Plio-pleistocene australopithecines (3.0 to 1.0 mya) - one type of hominin, of two or maybe more general types - australopithecines all shared a peculiar heavy back-teeth grinding adaptation, probably for hard seeds like grasses - large molars (and premolars) - reduced canines - zygomatic arches leave space for large temporal muscles - zygomatic arches are sturdy for attaching strong masseter muscles - fairly prognathic face - probably several different lineages - all went extinct, unless one led to humans - Some examples of australopithecines: - Australopithecus africanus (3.0-2.2 mya) - both South Africa and East Africa - enough fossils known that we can say a bit more about this species than others, such as: - still have marked sexual dimorphism in body size - even though their canines are reduced, probably to facilitate grinding
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Intro to Biological Anthro F 2011 / Owen: World full of Plio-pleistocene hominins p. 2 - this means that males no longer had much larger canines than females - but the body size difference suggests that there was still lots of male-male competition, so they were not monogamous - growth rings in tooth enamel suggest… - short, rapid juvenile development - similar to chimps, not humans - suggests that behavioral complexity and learning were more like chimps than like humans
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a201-11f-23-WorldFullOfPlioPleistoceneHominins -...

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