I don’t really understand your argument. Wearing dresses isn’t heritable, we know that because most women’s grandmothers wore dresses and most women wear jeans or casual wear.
Heritability isn’t proof that a trait is genetic, but it’s strong evidence once you start addressing confounding factors. As I recall, the IQ heritability research was done with twin studies.
This is like shocking to me we’re even debating this. I would have assumed it’s conventional wisdom.
Wearing dresses is heritable! Heritability is simply the ratio of genetically-caused variation to total variation for some trait across a population. Bad driving is heritable. So is risk aversion. So is musical taste. So is how much TV you watch. All of these: studied.
Traits can trivially be minimally heritable and totally genetically determined. The number of fingers on your hands is genetically determined by your Hox genes. But the variation in the number of fingers on your hand (more precisely: across the population) is overwhelmingly not genetically determined. Genetically determined, low heritability.
Traits can trivially be maximally heritable and not at all genetically determined. Whether or not you wear lipstick is largely decided by XY vs. XX. But there's no gene for wearing lipstick; if the cultural ball had broken a different way, we might all be wearing lipstick, or none of us. Genetically unencumbered, high heritability.
So: you haven't said anything. You're not even wrong. All you pointed out was that you can do a study and determine that population variations in intelligence (or bad driving, or social trust, or fear of dentists) are traceable to genetic variance. That doesn't mean that genes literally encode the outcome.
Heritability isn't "strong evidence". It's barely evidence at all. It's literally just a framing of the question, which your argument simply begs. Irresponsibly, at that. None of this should be news to you.
I don't even have to take a position on the blighted question of whether intelligence is genetically determined (or whether we can measure it meaningfully at all, or whether it's fixed at birth or fluid, or whether outcomes in intellectual performance are epigenetic). And I'm not. I'm just pointing out that your argument, the one I replied to, was literally vacuous.
> As I recall, the IQ heritability research was done with twin studies.
No, it wasn't. Such a set up is impossible because of lack of samples and sampling bias.
All that "IQ is X% heritable" means is that they ran a linear regression on a large data set and saw that the variance error in the regression reduced by X% when they plugged in parental IQ as a covariate in the regression.
This is a correlational study as causal studies are impossible. Correlational studies are inherently spurious and ignore lots of confounding factors. Nevertheless, we can say that what we routinely observe in real life - smart parents having smart kids, has been grounded in real data.
For getting effect of race on IQ you plug in race as a covariate. Typically, most of the race based IQ research remove parental IQ as a covariate. All of these regression based studies are dubious and there is no real way to correct it. A large data set of twins who were separated at birth could help, but there are caveats there as well.
As an aside, Jordan Peterson seems to love these race IQ regression models and likes to call them hard undeniable science. He immediately switched sides when talking about climate models and how these models can't be trusted, because the simple choice of covariate included creates absolutely unreliable and biased models.
We have relatively strong evidence for a significant degree of genetic determinism in athletic ability (at least for some sports). We do not for intelligence.
