Tuesday, May 23, 2006

Chicks dig dorks?   posted by JP @ 5/23/2006 09:46:00 AM

The most recent Current Opinion in Genetics and Development has a number of articles grouped around the theme "The sex chromosomes and human disease". A bit that might be of interest from this one:
The accumulation of intelligence (i.e. MRX) genes on the X might have occurred as the result of sexual selection - the choice of smart males by choosy females. Given that sexual selection is extremely rapid, this could explain the huge enlargement of the hominid brain over the past million years.

I'd heard the sexual selection argument for brain size before, but never in the context of genes for intelligence on the X chromosome. Apparently I should have, though, because they reference an article from 2001 as their source.

Here's the original hypothesis:
Therefore, regarding human evolution we propose the following model: one of the most important factors contributing to the uniqueness of human evolution is that at some point human females decided to select males according to their advanced cognitive abilities. The same cognitive abilities are selected for in the struggle for survival. In humans, the development of the mating characteristic is augmented by natural selection. This is an ongoing process with exponential acceleration, which will propel the development of general cognitive abilities in humans into areas we cannot imagine now

I think everyone can agree that the last bit about "exponential acceleration...into areas we can't imagine" is laughable, but what about the rest? Anything there?

I imagine natural selection acts quicker on X-linked genes than on autosomes anyways; it'll be interesting to see how people try to tease apart the two.

1. Razib had a thread about this on his other blog a little while back.

2. To answer the question in the comments about why they think this is sexual selection, the answer is pretty much that genes involved in reproduction are over-represented on the X as well. So, well, yeah. I'm not too convinced.

3. Interesting factoid: linkage studies don't usually look at the X. This one[pdf] certainly didn't. Something to ponder...