There's a new study published today in Science that tried to find the genetic causes (sources? underpinnings?) of same-sex sexual behavior. Maybe because they're not the first people to try this, and because bigoted pseudoscience is very much alive in 2019, the researchers tried to nip any PR problems in the bud. They created a website where you can click to find out "Who We Are" and "Why We Did This Study." And you know, good for them! Lots of things would benefit from a cool explainer site where anybody could poke around and get easy-to-understand digests of complex science. 

But I still feel uneasy about this.  How do you even define "same-sex sexual behavior"? The authors took a crack at it:

"In this study, we examined “same-sex sexual behavior,” which is defined as having ever had sex with someone of the same sex. “Same-sex sexual behavior” is related to, but not the same as sexual orientation and identity. Individuals in our study may have engaged in “same-sex sexual behavior”, and they may have a range of identities and personal reasons for engaging in this behavior. While our study includes many gay and lesbian individuals, it may also include those who sexual identify as bisexual, pansexual, straight, or one of many other identities."

This reads as an acknowledgement that sexual behavior is fluid and impossible to define. Many LGBTQIA scientists feel wary of this work themselves. Where does someone who identifies as gay but has never had sex with someone of their own sex (for common cultural reasons) land? What happens if they have sex for the first time at age 70? Do their genetics change? How does the sex spectrum play into this? Gender? I feel like I'm chasing my own tail just writing this. I can't imagine trying to do a large-scale genetics study with this set of wibbly wobbly definitions. Who does this even benefit? 

Again, to their credit, a lot of this is anticipated in their "What We Found and Limitations" section. They acknowledge that they grouped people into simple binaries, both in biological sex and in their sexual experiences. That's a problem! Anyone can tell you that's not how anything works. All human behavior, including "same-sex sexual behavior" is three-dimensional. Binaries fail. On top of that, the authors acknowledge that their biggest source of genetic data, the UK Biobank, itself has an enormous problem with selection bias.

No one else seems to know what to make of all this. Here's one set of headlines:

Here's another:

"No gay gene" and "multiple new genes linked to same-sex sexual behavior" are not mutually exclusive ways to read this. But so far, I don't understand the use of looking for genetic explanations for complex behaviors. There are so many problems, so few explanations, and so little real world impact.  But, there will be longer, more in-depth coverage of this soon. Maybe someone will find a use. In the meanwhile, the authors conclude:

"Comparing these GWAS results with those for the proportion of same-sex to total number of sexual partners among non-heterosexuals suggests that there is no single continuum from opposite-sex to same-sex sexual behavior."