Australopithecus sediba in the news

There are a couple of news articles on Australopithecus sediba. The first, at Science News concerns a presentation by Darryl de Ruiter at the AAPA meetings.

From Science News:

New A. sediba fossils from the same South African cave complex, many belonging to the previously discovered partial skeletons, underscore this ancient species’ mosaic anatomy, Berger said. A largely complete female pelvis displays relatively straight, vertically aligned hips and an elongated birth canal, much like early Homo species. Other Australopithecus females possessed a relatively short, wide pelvic opening and flaring hip bones.

New A. sediba foot bones include a chimplike heel and a humanlike ankle, Berger said. Fossils from the shoulders, rib cage and spine, as well as surprisingly long arm bones, typify Australopithecus.

At issue is the question of whether A. sediba represents a late surviving population of A. africanus or whether A. sediba evolved into Homo.

A press release from PhysOrg also mentions a presentation at the Paleoanthropology Society meetings. From PhysOrg:

Kristian J. Carlson discussed the size and shape of A. sediba’s brain, showing that by synchrotron scanning of the interior brain case, they were able to determine the estimated capacity to be around 420 cubic centimeters. This led to a very small brain size and is the reason researchers first determined these new skeletal findings to be in the Australopithecus genus. However, they also discovered that the frontal lobe of this small brain contained organization more similar to that of humans, showing that contrary to what was previously thought, organization and brain size with human characteristics may not have been a simultaneous change.

The pelvis of the A. sediba is what researchers believe show the strongest link toward the beginning of an evolutionary change to the Homo. Researchers have always linked the larger brain size of the Homo to the evolutionary change in the pelvic structure between the two. However, even with the small brain size and cranial structure of A. sediba, the pelvic structure has changed from previous Australopithecus to much closer to that of Homo.

More information on the scanning of the brain case would be interesting…

2 Responses

  1. Interesting articles. I always find it a little alarming how quickly many anthropologists get stuck into the taxonomy though, it implies a fixidity in species terms that is only useful retrospectively in the case of particular fossils, but not particularly so when looking at the realities of evolution. I know anthropologists are aware of this, it doesn’t seem to stop this kind of talk however.

    This is Homo. This is Australopithecine. Both relatively useless assertions when you are looking at fossils that most likely represent some point on the evolutionary scale between the ‘archetypal’ Australopithecine or Homo.

    These quibbles aside, I’m interested to see what further work on these fossils yields. The comments on the anatomy of the A. sediba foot are particularly interesting.

  2. I’m not so sure. the question of whether A. sediba is a chronospecies, represents a cladogenic event, or a small late surviving population does say something important about evolution.

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