a201-11f-22-EarlyAustralopithecines

a201-11f-22-EarlyAustralopithecines - Introduction to...

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Introduction to Biological Anthropology: Notes 22 Early Australopithecines Copyright Bruce Owen 2011 - A bit after 5 mya, one genus of hominins appeared and diversified into many species: the genus Australopithecus = “southern ape” - australopithecine refers to members of the genus Australopithecus in general, regardless of the species - often abbreviated as A ., for example Australopithecus anamensis = A. anamensis - earliest australopithecine: Australopithecus anamensis (around 4.2 to 3.9 mya) - mostly known from teeth, but some cranial, mandible, and limb fragments - upper and lower jaws and teeth were quite similar to apes - not very hominin-like - relatively U-shaped dental arcade (typical of other apes, not hominins) - but with some features that became typical of later australopithecines - reduced canines - relatively enlarged molars - thick enamel on the molars, indicating selection for grinding hard seeds - knee joint (top of tibia, or shin bone) suggests bipedalism - enlarged joint surface to withstand heavier use - concave joint surface limits twisting and side-to-side motions - ankle joint (bottom of tibia) also limits motion, as in bipeds - and elbow joint is like ours, rather than like apes that use arms for support on the ground - ape elbows lock in a straight position, the way our knees do - human elbows do not - and neither did A. anamensis 's elbow - so it probably did not lean on its arms much - which hints at bipedalism - We don’t know how these early hominins were related, and there were probably many more that we have not yet found fossils of - they just give us an impression of the general kinds of bipedal apes that led to later hominins - Early hominins snap into better focus around 4-2.9 mya with Australopithecus afarensis - the earliest bipeds that we have plentiful evidence of - The first discovery was a knee joint, which had details that suggested bipedalism - the team of Maurice Taieb and Don Johanson returned the next year to a place called Hadar and found the famous “Lucy” - an incredibly complete specimen - Lucy, an adult female, was a little over a meter tall (3' 3”), weighed around 60 pounds - with clear signs of well-developed bipedal locomotion - the next year, they found fossils of 13 more individuals in a single spot - the “first family” - maybe part or all of a group killed all together by some disaster, like a flash flood - additional A. afarensis fossils have been found since - not only in the original find area (the Afar depression), but also in other parts of Africa - so this was a successful, widespread species
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Intro to Biological Anthro F 2011 / Owen: Early Australopithecines p. 2 - all lived in environments ranging from a patchy woodland-grassland mix to an open grassland with only occasional trees - A. afarensis is often described as basically a bipedal chimp with some dental changes - A. afarensis had a mix of ancestral ape traits and some new traits that hinted at humans - ancestral traits (shared with other apes)
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This note was uploaded on 03/02/2012 for the course ANTHRO 201.3 taught by Professor Owen during the Fall '11 term at Sonoma.

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a201-11f-22-EarlyAustralopithecines - Introduction to...

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