"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 argument is that the metopic suture stays open in hominins longer to allow the brain to grow more postnatally, something we have known for some time. It is the new imaging techniques that have allowed us to get a better handle on this. The endocast has been around for almost ninety years and has been subject to all kinds of studies, some of which have led to riotous disagreements between researchers. More pieces of the puzzle.
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.
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