|Left to Right. Chimp, Taung, Modern Human. Credit: M. Ponce de León and C. Zollikofer/University of Zurich|
Today in PNAS endocast expert Dean Faulk and colleagues describe the results of a CT analysis on the Taung baby endocast (a specimen of A. africanus famously described by Raymond Dart as the first australopithecine). Because endocasts are the fossil impressions of the interior of ancient skulls, the team was able to determine that the Taung baby had an unfused metopic suture, just like modern human babies. It is very rare for this suture to be unfused in post-natal great apes. In modern humans, these unfused sutures are the reason baby heads can safely deform during birth (think coneheads), which allows humans to give birth to relatively large-brained offspring. It is interesting that this occurs in A. africanus, given that these guys are only a little bit bigger-brained than chimps. The authors suggest that it likely has to do with reorganization of the birth-canal associated with bipedalism.