(Sorry if someone's said this, I haven't read the whole thread in detail): to my mind, the best evidence for the mutability of IQ, i.e. for the importance of the whole environment on it, is the Flynn effect. It's obviously impossible for genetic change to account for anything like the magnitude of that effect, so those increases have to be environmentally caused, for the broadest possible definition of "environmentally". Of course, the observation may be of limited use (because, as the limited effects shown in intervention studies suggest, we are talking about the effect of the entire environment, i.e. growing up in today's world, not just about formal education, for example) and even of limited interest (because it's questionable how much the increase in what IQ tests measure reflects increases in what we really care about), but at least this shows that the idea that IQ cannot be affected by environment is wrong - the same sperm and egg combining in 1900 and growing up there would on average have a much lower IQ than that sperm and egg combining in 2011 and growing up here, if 1900s freezing technology had been up to it :-) [I'm saying sperm and egg, not baby, because one of the things that may be important is prenatal environment. I suppose I haven't accounted for sperm and egg quality issues other than genetics, but you have to start somewhere!]
