Friday, November 10, 2006

Update on earlier post

When I first read the article that this post referred to, a portion of it struck me as being potentially controversial:
They noted that this D allele is very common in Europe, where Neanderthals lived, and more rare in Africa, where they did not.

Which, given the import of the article (having the allele makes brains bigger) seems bound to not sit right with some. Turns out, I was right. This story (HT to Robin at The Perfect World) from the WJS a few months ago highlights it. Seems to be open access.

Scientist's Study
Of Brain Genes Sparks a Backlash

Last September, Bruce Lahn, a professor of human genetics at the University of Chicago, stood before a packed lecture hall and reported the results of a new DNA analysis: He had found signs of recent evolution in the brains of some people, but not of others.

It was a triumphant moment for the young scientist. He was up for tenure and his research was being featured in back-to-back articles in the country's most prestigious science journal. Yet today, Dr. Lahn says he is moving away from the research. "It's getting too controversial," he says.

What Dr. Lahn told his audience was that genetic changes over the past several thousand years might be linked to brain size and intelligence. He flashed maps that showed the changes had taken hold and spread widely in Europe, Asia and the Americas, but weren't common in sub-Saharan Africa.

Read the whole thing, as it goes into some more detail than the earlier article. This one suggests Lahn is more sympathetic to the allele = intelligence idea than the later one, perhaps because Lahn has been through the wringer already. Yet he does seem to favor at least something of a link:
While acknowledging that the evidence doesn't permit a firm conclusion, Dr. Lahn favors the idea that the advantage conferred by the mutations was a bigger and smarter brain. He found ways to suggest that in his papers. One mutation, which according to his estimates arose some 40,000 years ago, coincided with the first art found in caves, the paper observed. The other mutation, present mostly in people from the Middle East and Europe, and estimated to be 5,800 years old, coincided with the "development of cities and written language."

As others note in the article, that's fairly simplistic for a number of reasons, not the least of which is that many of the hallmarks of "higher civilization" appeared at different times in different places, often with no possibility of connection (e.g., the new world).

Clearly, the allele has some selective benefit to become fixed in the population, but what exactly it does and why it would be selected for doesn't seem adequately addressed as yet. So, watch for this.