Friday, April 09, 2010

Australopithecus sediba Articles in Science

The Science Magazine articles on A. sediba are out. They are free for the time being. You just have to register at the site. The two articles cover the morphology of the finds as well as the geology of the Malapa Cave, in which they were found.
There is an extensive list of traits listed of both the cranium and face tabulated along with the other australopithecine species and early Homo. According to Berger and his team, it tells us the following:
The closest morphological comparison for Au. sediba is Au. africanus, as these taxa share numerous similarities in the cranial vault, facial skeleton, mandible, and teeth (Table 1). Nevertheless, Au. sediba can be readily differentiated from Au. africanus on both craniodental and postcranial evidence.
The face has the scooped appearance of australopithecines, with nice anterior pillars and the cranium is small, with a size of about 420 cubic centimeters. For reference, our heads are around 1400 cubic centimeters in size. On the Homo side, however, the vault is expanded and the face is considerably narrower than that of your average australopith. Compare it to this front shot of Australopithecus boisei specimen OH5, taken by David Brill. This lateral flaring of the cheeks is characteristic of all australopithecines to one degree or another and is not found in early Homo at all.

From the neck down, the skull has a mix of australopithecine and early Homo traits. The australopithecine traits include comparatively long arms, a somewhat conical-shaped rib cage and a small stature. On the other hand, it has a pelvic structure much more like later Homo, suggesting even better walking and running abilities.

Berger and his team have, I think, correctly placed this critter in the genus Australopithecus, but it clearly does have some characteristics that presage early Homo. What those mean is not yet clear but there was a general shift toward more modern characteristics in all of these hominids at around 2 million years ago.

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