Researchers Say Human Brain is Still Evolving

Oleg Alexandrov writes "Two genes involved in determining the size of the human brain have undergone substantial evolution in the last 60,000 years, researchers say, suggesting that the brain is still undergoing rapid evolution. The discovery adds further 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."

Comments

Re:It's remarkable how wrong this is

[John Hawks]

Well, it sure might look that way, but these genes strongly suggest that something related to cognition was under strong selection throughout history.

One of the two genes, ASPM, appears to have come under selection only 5800 years ago; but it is now at around 20 percent, with a frequency of near 50 percent in some Near Eastern populations. Whatever this allele does, it had a selective advantage of more than 5 percent. They don't know it necessarily makes people smarter, but it's hard to think what else it might be.

That's really the neat part; that it shows that this idea of "survival of the dumbest" is apparently not what has been happening. Instead, there is every reason to think we have been getting smarter.

The submission doesn't mention the most problematic part: These alleles are high frequency in some populations, but absent or low frequency in others -- suggesting there may be adaptive differences in the brain among human populations. From my weblog post:

Geneticists are increasingly finding genetic variants that affect behavior. Several of these variants are now known to vary in frequency in different human populations. These alleles are two; the 7r allele of the dopamine receptor D4 (DRD4) gene is another that influences ADD/ADHD susceptibility (Harpending and Cochran 2002). The selective structure underlying DRD4 variation may be frequency-dependent, with different alleles correlating with alternative behavioral strategies that pose greater or lesser advantages in some populations. It is not clear whether such a mechanism is true of ASPM and Microcephalin; the selected alleles have risen to such high frequencies in some populations that it seems they are not mere alternatives; they are unilaterally advantageous -- at least where they have become common already.

--John