Bite makes way for brain
A single mutation may have caused gross anatomical changes that spurred
human evolution
By Brendan A Maher
March 24, 2004

A pile of evidence from disparate disciplines indicates that a single change
in a single gene-MYH16-may be responsible for significant morphologic
differences between humans and other primates, including possibly the
three-fold increase in brain size that set the earliest species of Homo
apart from their kin. This is the first protein disparity between humans and
chimps that can be correlated to drastic anatomical changes seen in the
fossil record, according to a group of University of Pennsylvania
researchers who published a letter in the March 25 issue of Nature.

"This is a brilliant piece of detective work that has enormous implications
for medicine, biology, evolution, molecular genetics, [and] the human
genome," said Frederick S. Kaplan, a professor of orthopedic molecular
medicine at Penn who was not part of the study. "By relegating a gene to the
evolutionary garbage heap, we were able to lift the constraints to the
development of human complexity," he told The Scientist.

Powerful muscles for biting practically dominate the cranial structures of
most primates, including gorillas, chimps, and extinct Australopithecus and
Paranthropus species. A gene responsible for a majority of jaw musculature
was lost from human ancestors, presumably 2.4 million years ago, according
to the study. Drastic reductions in these muscles may have lifted
significant physical constraints on braincase volume, allowing primates with
weak jaws and big brains to eventually think about their origins.

Read the rest at The Scientist dot com
http://www.biomedcentral.com/news/20040324/04

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