The abstract concludes a little differently:
Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species.
Not the same thing at all. What they actually measured was
Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples.
This team includes some of the same researchers that claimed that having boys reduced the mother's lifespan, even if the boy died in infancy--which was tentatively blamed (by Lummaaa) on testosterone's effect on the mother. Although she admitted it was clearly more complicated than that.
5 comments:
I do think there's good evidence for natural selection in the last 10,000 years, though. The global differences in genetic predisposition to diabetes and lactose intolerance line up well with broadly regional differences in diet since the beginning of agriculture.
With catastrophic events such as plagues, you might get measurable selection fairly rapidly. In more stable times, the signal-to-noise problem would be too much, I suspect.
There is some belief that the extra IQ points of Ashkenazi Jews came about relatively quickly under selective pressure in (I think) the 13th-15th C's.
I don't know. There's a persuasive pattern among cultures that adopted agriculture early and late, in terms of how well they hold up to a diet of grains and milk products. A useful gene that protects against diabetes or lactose intolerance can spread very quickly through the populations as soon as it's time for it to do some good. And nothing but selective pressure can explain the retention of the sickle-cell anemia gene in African populations, so fatal in double doses and so useful against malaria in single doses. "The 10,000-Year Explosion" by Cochran & Harpending makes a good case for a number of traits like these.
If you could get substantive changes in 100 years I'd think sickle-cell would be gone by now. I wasn't thinking on larger time scales; just the one in the study.
Agreed -- I wouldn't expect to see much in 100 years. But I wouldn't expect to see zero, either. That could be five generations, and animal husbandry shows at least some effects that fast.
Post a Comment