Comment by tptacek
5 days ago
This literally doesn't say anything. It's a lot of words, but you've managed to reproduce the exact position the author of the article has. For those wondering what the trick was here: this comment forwards the 40-80% h2 numbers from twin studies, then says "molecular genetics show real, replicable genetic signal for intelligence", rather than showing the 10-30% h2 numbers those studies generate.
It's practically nobody's position that there's no linkage between genetics and intelligence (that would be weird indeed), but it's important for this comment for you to believe that's the counterargument --- otherwise the comment doesn't make sense.
The real question is whether genetics is a substantial or a negligible influence on intelligence (or proxy measures like IQ).
If genetics is less than 5 percent I would consider that something worth ignoring.
If it is 10 percent it is substantial enough to make a difference at the extremes.
If it is 20 percent that is real serious business.
Anything higher means we should really sit up and take notice of this fact.
Another issue is, what is it that you're trying to use it for?
If you're arguing against a eugenicist then it's not just about the percentage, in that case you have to distinguish between genetic and heritable. Suppose that there are some set of four genes that, in just the right combination, are worth 5 IQ points. That's, by definition, genetic, but it won't have a strong correlation with heritability because every kid has four chances to get the combination wrong. Or, if the combination does something bad, four chances to get it right even if their parents didn't. So past performance is no guarantee of future results.
By contrast, if you're trying to decide whether to allocate more resources to kids who already show promise, you care about the individual's natural potential rather than the statistical probability that it will be similar to their parents, so it doesn't matter what was more likely, it matters what actually happened. And by the point you're performing the evaluation, you can't go back in time and change things like the prenatal environment for someone who is already born, so in that context those things belong in the "nature" column and "nurture" only gets the things you could still affect.
Please look at the examples in the article and consider re-calibrating your numbers here. The lower range of heritability means that it is mostly noise.
Why is that? Odd that the article claims otherwise:
> 50% may sound like a solid heritability figure, but the associated correlation is rather modest.