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Steve Pittelli, MD's avatar

If you only had twin studies to work with, then you could still keep this position. The fact, though, is that genetic studies have not supported the conclusions of twin studies. Whether you want to call that an absolutist position or quibble about the validity of even the tiny correlations found in a typical GWAS, they strongly contradict the high heritability claims from twin studies. This is all without looking at it the other way, which is that twins often have wildly divergent personalities even with an identical genetic makeup. The fact that people born at the same time can have very different personalities and fates was the central argument for Cicero to reject astrology, so one can ask who the astrologers are when logic is stretched to explain the differences in identical twins? If one MZ twin has Huntington’s Chorea, the other will have it 100 percent of the time. Looking for some wobbly stochastic explanation is only a response to failed genetic studies. What we really have here is a philosophical question about human nature. Taking tiny findings (which, as we know, don’t generally hold up) and bolstering them, often to major media outlets, promotes a deterministic fantasy of what humans are, but if there was no philosophy here, scientists would be calling behavioral genetics a failed hypothesis. The fact that identical twins are found to be more alike than fraternal twins in studies (leaving aside that any pair of twins we know individually have obvious differences), is an interesting “paradox”, but we already know that the reason is not that they share causal genetic variants. There is no point in holding onto the idea that genetics are going to explain who we are as human beings other than ideology.

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Stetson's avatar

Isn't Jay Joseph the psychologist that argues that genetic variation plays no role in schizophrenia? Bit of an RFK Jr position there...

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