> Heritability does not imply the existence of a genetic mechanism. Twin studies have a number of flaws that further demonstrate my points about standards of me

> Heritability does not imply the existence of a genetic mechanism. Twin studies have a number of flaws that further demonstrate my points about standards of methodology that geneticists wouldn't touch with a ten foot pole. Even not taking into account stuff like equal environment assumption, identical twins simply do not have the same DNA. Yes, even identical twins, look it up. There are also a number of things that are heritable without involving a genetic mechanism at all, such as the various microbiomes or epigenetics. And of course there are things like transmission of de novo mutations over up to two generations (e.g. affecting germinal cells of one's fetus). ...I think you're missing how twin studies work, here. Yes, they can't distinguish between epigenetic and genetic traits, but they DON'T require twins to have identical genetics, and DON'T require equal environments. Specifically, they work by 1. Measuring the correlation in identical twin IQs (or other traits) 2. Measuring the correlation in fraternal twin IQs (or other traits) 3. Comparing the correlations. If identical twins have a 50% correlation and fraternal twins 25%, well... Identical twins not having identical genetics makes it harder to find genetic influence, but doesn't make it impossible. (it just means that the twins share 99.9...% of varying DNA instead of 100%, which is still far above fraternal twins and enough to establish a difference) And the reason you use twins is to control for varying environments. (And for that matter both identical and fraternal twins will share germinal cells/microbiomes/etc, too) Yes, it's fuzzier than a physics experiment. But it's certainly not worse than "this gene causes a 0.1% increase in the chance of breast cancer".