The scientists make their claim based on the recent evolutionary history of two genes -- microcephalin and abnormal spindle-like microcephaly-associated (ASPM) -- which appear to regulate brain size.

This class of microcephalin mutations first emerged approximately 37,000 years ago, while the ASPM variant class was estimated to have arisen about 5,800 years ago.

The microcephalin variant was also found with higher frequency outside of sub-Saharan Africa. (Gosh, Africans are taking it on the chin these days what with The Bell Curve, New Orleans disaster and such. - ed.)

The researchers stressed, however, that no inferences could yet be drawn about the relative genetic evolution of one ethnic group over another, since many as yet unidentified genes probably play a significant role in brain development.

"We think each gene conveys some sort of fitness advantage in brain biology. It could be an improved cognitive function or a personality trait. We're not sure. But we know whatever consequence they render is highly favored by selection."

The researchers concluded that the overall genetic history of these two brain gene mutations is evidence that the brain is most likely still evolving in terms of size and complexity.

"In another 10,000 or 20,000 years, I think the human brain may acquire a form that is quite different than the human brain today," Lahn said. "Not necessarily in its shape, which may remain relatively the same. But the function may be different. It may be, on average, a little smarter.