Cosma Shalizi (2007): Those Voices Again: "Q: Do you ever get tired of beating that dead horse?
A: It's not dead yet; that horse will keep kicking until the last person who thinks there's something to The Bell Curve is hanged in the entrails of the last Durkheimian.
Q: I really did not need that image, thank you very much. So you're perfectly happy to agree that there is genetic variation in the human population which affects the facility with which various cognitive skills are learned, and so mental ability?
A: Sure. In a more cautious mood, instead of saying "there is" I'd say "there could be, for all we know at present, which seems to be squat". But, sure.
Q: And yet, miraculously, this genetic variation is somehow not under natural selection?
A: Did I say anything of the kind? I can think off the top of my head of a really obvious example of recent human evolution, and gene-culture co-evolution at that, namely the four independent evolutions of adult lactose tolerance. For that matter, over the last, oh, 515 years basically the whole human population has been put under intense selection pressure for immune systems which easily develop resistance to smallpox. My guess is that this sort of thing overwhelms any selection pressure for, say, facility of learning symbolic arithmetic (in which symbol system, by what pedagogical method?), unless there are truly weird pleiotropic genes in play....
Q: Could there be traits under selection in the present?
A: I am pretty sure that genes contributing to resistance to malaria, cholera, schistosomiasis and malnutrition continue to be positively selected.
Q: Any more interesting suspects?
A: The prospects for influenza resistance look bright.
Q: You know what I meant.
A: You're asking me to pull speculations out of the air.... People are going to think I'm advancing a genetic explanation for the Flynn Effect, when it's much too strong for it to be due to any remotely plausible degree of selection...