[A_D_E_P_T]

Farmers, who depend on this sort of thing, have it figured out:

> https://extension.missouri.edu/publications/g2910

Heritability is simply a measure of how much of the variation in a trait, like height or IQ, is due to genetic factors rather than environmental influences in a given population. Could be feedlot steers, could be broiler chickens, could be humans. In humans, traits like height are very highly heritable, at ~0.8. Certain others, like eye color, are heritable to ~0.98.

[tptacek]

Right. It's a simple ratio of genetic variation to phenotypical variation. How does evidence of heritability support HBD claims, which are based on genetic determinism, a notion orthogonal to heritability?

[A_D_E_P_T]

I don't think that HBD claims -- at least, those made in reasonably good faith -- are based on genetic determinism. A Bosnian guy from the Dinaric alps is much more likely to be >1.8m in stature than a Pygmy. This is not predetermined as such, it's just that one population has something like +3SD in stature over the other. (An admittedly wildly extreme example!)

Differences in IQ between groups are apparently far more modest, but, however distasteful, it's still possible to speak of them, and it's possible to make statistical statements about them. My position is simply that, on the one side, it should be done in good faith -- and, on the other side, it shouldn't be seen as something heretical.

[tptacek]

I don't understand the alternative interpretation you're alluding to. Stipulate the validity of IQ or the common g. If group variations in these metrics aren't caused by genes, why are they distasteful? If they are, you're describing genetic determinism, which, again, is orthogonal to heritability.

[A_D_E_P_T]

Heritability is a statistical concept, not a measure of genetic determinism. High heritability doesn’t imply that a trait one exhibits, such as IQ or height, is entirely predetermined by one's genes. Even eye color is only heritable to ~0.98. I'll grant that any trait heritable to 1.0 is indeed entirely predetermined by one's genes -- though, offhand, I'm not sure that such traits exist in humans.

That aside, we're getting into semantics. Whether you call it "genetic determinism" or "heritability," we're talking about durable group differences in genetically-mediated traits. And that is what people may find distasteful or even heretical.

[tptacek]

Are we talking past each other? I'm saying: heritability is orthogonal to the question of whether a trait is determined by genetics. There are traits with no genetic component at all that are highly heritable, and vice versa. "Genetic determinism" doesn't mean "a guarantee that a group of genetically similar people will display a trait"; it means "the trait is causally linked to genes".

The semantics matter, because the evidence supporting HBD positions is stated in terms of the technical definition of heritability.

While I've got you, can I ask that you stop evoking "heresy" and "distaste" in this thread? I believe I'm making simple, objective points, not summoning opprobrium on your position.

[A_D_E_P_T]

Sure, heritability is orthogonal to the question of whether a trait is determined by genetics.

But traits like IQ, height, and eye color are both (A) highly heritable and (B) substantially shaped by genetic factors. In casual online discourse, I believe that (B) is usually taken for granted, so it's glossed over, and when people say that any given trait is "heritable" they're also assuming that (B) is true for the trait. At least, I am guilty of that lapse.

And I take your point about language.