[thraway180306]

Why cherry-pick? Where is the Spanish? Is this a heritability study by someone who just outright denied any foreign languages being spoken in the USA?

The natural experiment was conducted by Omniscient Statistician? This was published somewhere?

You do realise that heritability has no sense outside particular time, particular controls and particular populace? There is no number to heritability (in particular not 0) unless you precisely specify on what probe (and that number is only valid to that specific probe). These are not constants but relative variables being measured.

Let me illustrate that with Flynn's effect of IQ increasing over the last century. A today's IQ test administered on 1950's populace would average below 100. In populace today heritability of IQ test-taking was measured to be something. If one were to combine these two populaces, the distribution's variance partition would change (the distribution would become bimodal, with new environmental factor: whether someone is from today or the 50's). Suddenly heritability would be severely diluted by the new environmental factor. Does that make existence of heritability suspicious? No. Does that invalidate your estimates? Yes.