Cosma Shalizi has a mammoth post intended inter alia to explain precisely what is at stake in debates over heritability and IQ to those whose eagerness to pronounce winners in these debates is not, perhaps, matched by their grasp of the underlying methodological issues. Takeaway point:
Do I really believe that the heritability of IQ is zero? Well, I hope by this point I’ve persuaded you that’s not a well-posed question. What I hope you really want to ask is something like: Do I think there are currently any genetic variations which, holding environment fixed to within some reasonable norms for prosperous, democratic, industrial or post-industrial societies, would tend to lead to differences in IQ? There my answer is “yes, of course”. I’ve mentioned phenylketonuria and hypothyroidism already, and many other in-born errors of metabolism also lead to cognitive deficits, including lower IQ, at least in certain environments. More interestingly, conditions like Williams’s Syndrome, Downs’s Syndrome, etc., are genetically caused, and lead to reasonably predictable patterns of cognitive deficits, affecting different abilities in different ways. … I suspect this answer will still not satisfy some people, who really want to know about differences between people who do not have significant developmental disorders. Here, my honest answer would be that I presently have no evidence one way or the other. If you put a gun to my head and asked me to guess, and I couldn’t tell what answer you wanted to hear, I’d say that my suspicion is that there are, mostly on the strength of analogy to other areas of biology where we know much more. I would then — cautiously, because you have a gun to my head — suggest that you read, say, Dobzhansky on the distinction between “human equality” and “genetic identity”, and ask why it is so important to you that IQ be heritable and unchangeable.
Rick Perlstein demonstrates exactly how to do the devastating book review in his account of two right-wing revisionist histories of Vietnam.
The Pentagon Papers were quite certain and cited convincing evidence: “The Catholic deputy province chief ordered his troops to fire…. The Diem government subsequently put out a story that a Viet Cong agent had thrown a grenade into the crowd and that the victims had been crushed in a stampede. It steadfastly refused to admit responsibility even when neutral observers produced films showing government troops firing on the crowd.” The instigator was a Vietcong agent, Moyar insists. How does he know? By inference, not by evidence. He claims the monasteries were lousy with Communist infiltrators, even, perhaps, among their highest counsels. And how does he know that? The Communists said so. It is more than passing strange. On one page Moyar knows what every good right-winger knows: Communists are liars (“With characteristic exaggeration a Communist history stated that…”). On others, however—it is one of the reasons conservative reviews have found him so impressive—he uncritically accepts Communist sources as his key proof texts.