A reanalysis of the South African australopithecine natural endocasts.

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Sulcal patterns of six previously available South African australopithecine natural endocasts are reexamined and compared to sulcal patterns of 17 human, 12 gorilla and six chimpanzee brains. In addition, a seventh natural endocast, from STS 58, is described for the first time and compared to an artificial endocast from the same specimen. Using the Taung endocast as a focal point, it is shown that sulcal patterns reproduced on natural endocasts of australopithecines appear to be pongid-like rather than human-like. Contrary to earlier descriptions, the lunate sulcus occupies a rostral position similar to that found in pongids. Since South African australopithecine brains do not appear to be reorganized along human lines at a gross external neuroanatomical level, the concept of neurological reorganization is best applied at finer neurological levels, perhaps at the level of the neuron or at a neurochemical level. Thus, future studies by comparative neuroscientists are more likely to elucidate the fine details of neurological reorganization that occurred during early human evolution than are studies by paleontologists who directly observe the australopithecine fossil record of natural endocasts.