Article: Brain May Still Be Evolving, Studies Hint
- Brain May Still Be Evolving, Studies Hint
By NICHOLAS WADE
Published: September 9, 2005
Two genes involved in determining the size of the human brain have undergone substantial evolution in the last 60,000 years, researchers say, leading to the surprising suggestion that the brain is still undergoing rapid evolution.
The discovery adds weight to the view that human evolution is still a work in progress, since previous instances of recent genetic change have come to light in genes that defend against disease and confer the ability to digest milk in adulthood.
It had been widely assumed until recently that human evolution more or less stopped 50,000 years ago.
The new finding, reported in today's issue of Science by Bruce T. Lahn of the University of Chicago, and colleagues, could raise controversy because of the genes' role in determining brain size. New versions of the genes, or alleles as geneticists call them, appear to have spread because they enhanced brain function in some way, the report suggests, and they are more common in some populations than others.
But several experts strongly criticized this aspect of the finding, saying it was far from clear that the new alleles conferred any cognitive advantage or had spread for that reason. Many genes have more than one role in the body, and the new alleles could have been favored for some other reason, these experts said, such as if they increased resistance to disease.
Even if the new alleles should be shown to improve brain function, that would not necessarily mean that the populations where they are common have any brain-related advantage over those where they are rare. Different populations often take advantage of different alleles, which occur at random, to respond to the same evolutionary pressure, as has happened in the emergence of genetic defenses against malaria, which are somewhat different in Mediterranean and African populations.
Full Text at The New York Times
Robert Karl Stonjek
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