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Why would the “what if inter-generational wealth” point impact what twin studies and such show? If the correlation between the measured IQ of monozygotic twins is substantially more than between other siblings, how would wealthy/poor ancestors impact that? Even if wealth had an impact on the probability of having twins, I still don’t see how that would result in the correlation between twins being more, even when raised apart.

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I had other studies in mind (done in China) regarding that specific point, it's what I had assumed a lot of posters here were referring to because it's normally a favorite of people who are eager to jump to certain conclusions about genetics.

There are other problems with twin studies, most importantly that developmental health starts at conception which means that genetics are not the only thing that twins are sharing. Once again I'll refer you to Wikipedia for further criticisms of twin studies:

https://en.wikipedia.org/wiki/Twin_study#Criticism

The heritability estimates have also been done between biological parents, adoptive parents and their children and using comparisons between siblings and half siblings.

There have been many many papers from many angles on this over the years. The high heritability seems to be a well established fact.

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