The origins of human intelligence?

Researchers have proposed an answer to the vexing question of how the human brain grew so big. We may owe our superior intelligence to weak jaw muscles, they suggest.

A mutation 2.4 million years ago could have left us unable to produce one of the main proteins in primate jaw muscles, the team reports in this week's Nature. Lacking the constraints of a bulky chewing apparatus, the human skull may have been free to grow, the researchers say.

The timing of the mutation is consistent with rampant brain growth seen in human fossils from around 2 million years ago, says Nancy Minugh-Purvis of the University of Pennsylvania in Philadelphia, who helped with the study. "Right at the point you lose power in these muscles, brain size evolution accelerates," she says.

Here is the full story. Here is the original research. Here is another account, which also reports on the critics of the idea. My gut level lay person's response is not to believe the hypothesis, but hey, try convincing a physicist of the notion of comparative advantage.