Heritability is precisely specified. It allows you to make predictions within its realm of validity. It's useful and so it is used. If you know my genome, and

Heritability is precisely specified. It allows you to make predictions within its realm of validity. It's useful and so it is used. If you know my genome, and you know the broad social environment I live in, you can make more accurate predictions about my obesity than if you only know my social environment. > This is no mere statistical fine point: it means that the entire project of assessing how essentially genetic traits are in terms of measured heritability coefficients is a fool’s errand. The key word in this statement is "essentially," which in this context is being used to mean "fundamentally." But we DO know something about the environment, so it doesn't matter if heritability is a "fundamental" measure, if all you want to do is use it to make predictions about things. If you live on an Earth that has food on it you can expect that the heritability of "starves to death" is different than if you live on an Earth that does not have food on it, in which case heritability is undefined because everyone dies (no variation, divide by zero). Similarly, if you have performed your heritability studies in a modern Western society then that heritability estimate remains valid for people drawn from that society despite the fact that it is not an "essential" measure of anything. None of this contradicts the quotes that you have included, but I want to make sure people understand that there is actually a reason we use heritability, it matches intuitions so long as your environment is fixed or similar, and that it does actually provide us with information about the world we live in. It doesn't tell you how controllable a phenotype is through environmental factors, but it does tell you how much it's being controlled right now.