"Heritability" is a funny concept which is easy to misunderstand. http://bactra.org/weblog/520.html

> Heritability is a technical measure of how much of the variance in a quantitative trait (such as IQ) is associated with genetic differences, in a population with a certain distribution of genotypes and environments. Under some very strong simplifying assumptions, quantitative geneticists use it to calculate the changes to be expected from artificial or natural selection in a statistically steady environment. It says nothing about how much the over-all level of the trait is under genetic control, and it says nothing about how much the trait can change under environmental interventions.

In addition, heritability, what claims can be inferred from its measures, and the meaning of those claims in discussions like in this thread are also a tricky concept when investigated from a philosophical standpoint[0][1], and some measures (and of course proposed solutions) have been controversial among sociobiologists, evolutionary biologists, and philosophers alike.

[0] https://plato.stanford.edu/entries/heredity/#PhilIssuArisTwi...

[1] https://mitpress.mit.edu/books/beyond-versus

If I had a lot more time I'd like to take a longer look at that link and make a list of all the fallacies and dark patterns it uses. As it I just managed to glance that it first sets up a narrow, technical definition of heritability which then proceeds to criticise. That's a pretty standard dark pattern.

Whatever his definition is, what we mean in this conversation is that smart parents tend to have smart children, and dumb parents tend to have dumb children, and that there's little one can do with the environment (besides minimum nutrition) to change that.

I'm sorry, but I meant a source other than a 2 hour video criticising a book. And before you say it's a good video, I actually tried watching it once. I think I got through about 30 minutes of saying nothing of substance when I gave up. I actually recommend the exercise - try rewatching and make a note when he actually makes an argument or references a source.

Right above my comment is another linking the wikipedia page on IQ heritability. That would be a good example of a source. Meta-studies are a good option. Longitudinal studies are a decent one. Single studies are usually useless, but they're at least a good starting point for a productive conversations.