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harpend comments on Q&A with Harpending and Cochran - Less Wrong
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You are even meaner than Shulman. We don't know how human intelligence evolved and we need to know it in order to answer your question I think. This is where evolutionary psychology and differential psychology (Am I using that term right?) must come together to work this out.
We think that we know a little bit about how to raise intelligence. Just turn down the suppression of early CNS growth. If you do that in one way the eyeball grows too big and you are nearsighted, which is highly correlated with intelligence. BRCA1 is another early CNS growth suppressor, and we speculate in the book that a mildly broken BRCA1 is an IQ booster even though it gives you cancer later. BTW Greg tells me that there a high correlation between IQ and the risk of brain cancer, perhaps because of the same mechanism.
But these ways of boosting IQ are Red Green engineering. (Red Green is a popular North American comedy on television. The hero is a do-it-yourselfer who does everything shoddily.)
On the other hand IQ seems to behave like a textbook quantitative trait and it ought to respond rapidly to selection. We suggest that it did among Ashkenazi Jews and probably Parsis. IQ does not seem to have a downside in the general population, e.g. it is positively correlated with physical attractiveness, health, lifespan, and so on. Do we get insight into the costs of high IQ by looking at Ashkenazi Jews? Do they have overall higher rates of mental quirks? Cancer? I don't know.
HCH
That's interesting. I found a 2006 paper which argued that a genetic mutation is responsible for myopia, and that it also increases intelligence, but the specific gene and mechanism involved were apparently still unknown at that time. Has there been some more recent research results on this topic?
There is apparently a research group in China that has some solid results but I have not seen them and do not know if they are out yet.
HCH
They're engaged. :)
There is now substantial evidence that there is a causal link between prolonged focusing on close objects - of which probably the most common case is reading books (it appears that monitors are not close enough to have a substantial effect) - and nearsightedness/myopia, though this is still somewhat controversial. This is the typical explanation for the correlation between myopia and IQ and academic achievement.
A genetic explanation is possible, and would be fascinating, but I wouldn't want to accept that without further evidence. If the genetic explanation is true and environment makes no contribution, then I think one should find that IQ is more highly correlated with myopia than academic achievement -- I don't know if this has been found or not.
It's like saying "if evolution is true, crocoducks should exist". You are (deliberately?) misrepresenting opponent's views. He meant that of all genetic variation affecting IQ, only small, but non-negligible, subset affects both myopia and IQ. However I still don't quite get how larger brain can cause myopia rather than hyperopia.
Maybe the larger brain leads to more intelligence, and people with more intelligence read more, and reading more leads to myopia. (Whether reading actually leads to myopia can be questioned, but that doesn't affect the point.)
More correlated than academic achievement is correlated with IQ, or with myopia?
Your comment is a very good point. But IQ may be more-closely correlated with academic achievement than academic achievement is with reading books; so this comparison might not help. (And you want to talk about the variance in X accounted for by Y but not by Z, rather than place a bet on whether Y or Z has a higher correlation with X.)
Yes, of course. But remember that in science we are not in the business of "accepting" one thing of another. That is the domain of religion and politics. The only thing that matters is finding good hypotheses and testing them.
HCH