Weaker Jaws Were Traded for Big Brains

Thursday, March 25th, 2004

We may owe our amazing human mental powers to a mutation that weakened our ancestors’ jaws. From Weaker Jaws Were Traded for Big Brains:

A genetic mutation that occurred 2.4 million years ago could be the reason why modern humans have such big brains and weak jaws, scientists said on Wednesday.
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All humans have the MYH16 mutation but other primates, including chimpanzees and macaques, still have the intact gene. Over the past few million years, since the genetic fault occurred, human skulls have grown three times in size and the outwardly elongated jaws have receded.
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“The coincidence in time…may mean that the decrease in jaw muscle size and force eliminated stress on the skull which released an evolutionary constraint on brain growth,” said Nancy Minugh-Purvis, a member of the team at the University of Pennsylvania School of Medicine, that made the discovery.

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