Thread by @evolbrain

Goodbye gay gene.

There's a fascinating study out today that examines the genetics of sexual behavior. This is in many ways a model of what responsible research on vulnerable groups can look like. The science is pretty remarkable too. science.sciencemag.org/content/365/64…

There is a long list of researchers involved in this, and I want to recognize their rigorous and thoughtful work. They include @andganna, @bmneale, @jrbperry, @michelnivard, @robbeewedow, @RobertMMaier, @dr_appie, @dralexbusch

@andganna @bmneale @jrbperry @michelnivard @robbeewedow @RobertMMaier @dr_appie @dralexbusch The study looks at nearly 500,000 people from @ukbiobank, @23andMeResearch & other sources, to examine responses to a question: "Have you ever had sex with someone of the same sex?" They find a substantial amount of heritability that largely fits expectations.

So based on families, heritability is 36%. Based on SNPs, 8-25%. It's substantial but far less than say height. Polygenic scores could account for less than 1% of behavioral differences. Turns out we are not genetic automatons.

One of the really exciting developments is the use of genetic correlations to examine biological overlap among traits. Applied to sexual behavior, they found some very, very cool things.

The Kinsey scale normally goes from exclusively heterosexual to exclusively homosexual, for example. But the genetic markers associated with different points along the scale are different. There are lots of dimensions of biology that shape sexual choices.

People who sometimes have same-sex encounters have genetic markers associated with more partners overall, or with being more exploratory. But genetic markers for exclusively same-sex behavior are unrelated to personality. Some of us are probably more flexible than others.

And one fascinating part of the story is that there is a genetic correlation between same-sex behavior and mental health. Presumably this is because people who have same-sex partners are more likely to experience stigma & prejudice, which in turn puts them at risk for depression.

This is a powerful example of how cautious we need to be when thinking about the genetics of complex traits. Biology shapes us only in dialog with our personal stories. Our histories. It contributes to how the world treats us and how we respond to that treatment.

One major concern about studying the biology of sexual orientation (or sex behavior more narrowly) is that there is a deep history of using science to advance bigoted agendas. We are right to be wary.

First, there is the concern that scientists will be biased. We bring our own biases to the hypotheses we propose & the way we interpret our results. The solution to that, however, is not "stop this science," but partner with the people you are studying.

These "community-based research practices" make the science both more humane and more rigorous.

A second concern is what happens with the knowledge we gain. This is a moral question for us to resolve as a society, and it is by no means limited to sexual desire. How do we ensure that these data are not the basis for discrimination? Of embryo selection or manipulation?

The good news is that we are a long way from these data being actionable from the standpoint of bad actors. You just can't predict someone's behaviors from their DNA.

Read more in @PamBelluck's lovely summary just out in the @nytimes
nytimes.com/2019/08/29/sci…