One of the world’s most important fossils has a story to tell about the brain evolution of modern humans and their ancestors, according to Florida State University evolutionary anthropologist Dean Falk. The Taung fossil — the first australopithecine ever discovered — has two significant features that were analyzed by Falk and a group of anthropological researchers. Their findings, which suggest brain evolution was a result of a complex set of interrelated dynamics in childbirth among new bipeds, were published May 7 in the Proceedings of the National Academy of Sciences. “These findings are significant because they provide a highly plausible explanation as to why the hominin brain might grow larger and more complex,” Falk said.
The first feature is a “persistent metopic suture,” or unfused seam, in the frontal bone, which allows a baby’s skull to be pliable during childbirth as it squeezes through the birth canal. In great apes — gorillas, orangutans and chimpanzees — the metopic suture closes shortly after birth. In humans, it does not fuse until around 2 years of age to accommodate rapid brain growth.
The second feature is the fossil’s endocast, or imprint of the outside surface of the brain transferred to the inside of the skull. The endocast allows researchers to examine the brain’s form and structure. After examining the Taung fossil, as well as huge numbers of skulls belonging to apes and humans, as well as corresponding 3-D CT (three-dimensional computed tomographic) scans, and taking into account the fossil record for the past 3 million years, Falk and her colleagues noted three important findings: The persistent metopic suture is an adaptation for giving birth to babies with larger brains; is related to the shift to a rapidly growing brain after birth; and may be related to expansion in the frontal lobes.
via Anthropologist finds explanation for hominin brain evolution in famous fossil.
