Why Does the Search for a Gay Gene Freak Everyone Out?

For some reason, equipment like this freaks people out.

Photo by Philippe Huguen/AFP/Getty Images

This article originally appeared in The Conversation.

Why does a “gay gene” paper still cause a stir? A similar paper on any other topic would probably have passed unnoticed. But this is sex research—where public interest is huge but real funds and real science are very scarce and stories get recycled.

A study that is not even yet a paper was presented in preliminary form on Valentine’s Day by sex researcher Mike Bailey at a conference in Chicago. It said there is a genetic component to homosexuality. In fact, the study of 400 pairs of brothers where at least one was gay confirmed a smaller, controversial study from 20 years before and several twin studies in between. (The 1993 study led the Daily Mail to run one of its most infamous headlines: “Abortion hope after ‘gay genes’ finding.”)

The Bailey paper claims to have found large segments of chromosomes containing hundreds of genes that are common in gay men. The researchers admitted they couldn’t find any specific “gay genes.”

Last year, a paper in a relatively obscure journal also caused a public stir for saying just the opposite. The authors came up with a complicated biological explanation for why gay men have more female relatives, tend to have older brothers, and why it involves testosterone in the womb and runs in families. Controversially, they said it wasn’t due to their genes but to small chemical signals that alter the genes (called epigenetics), which can pass from one generation to the next, and had some (unclear) evolutionary advantage.

The study was undoubtedly clever and involved high-powered math, but it was purely theoretical, didn’t involve real people, and made false assumptions leading to fatal flaws.

This latest round of reporting following the Bailey research has led to perhaps inevitable criticism that we have an obsession with male homosexuality.

One reason people react so violently to these studies is a lack of understanding of basic biology and science, and realizing that homosexuality is for a scientist just another human characteristic or trait, like sporting ability, obesity, optimism, or depression.

Almost all human traits studied have some genetic (heritable) component, usually in the range of 30 to 70 percent. Homosexuality in males and females has a heritability in most studies of around 30 to 40 percent, with plenty of room for environment. And there is no single gene for any of these traits.

We have about 20,000 genes (about the same as worms) and thousands of genes influence each behavioral trait to tiny extents. So whether you believe it or not—the “gay gene” is a joke. No genes have actually been found to consistently influence homosexuality solely because genetic studies have been far too small; it took more than 34,000 people and 20 labs to find one little gene variant that influenced 0.1 percent of blood pressure—wow.

While researching Identically Different, my book on the effect of epigenetics on twins, I interviewed several sets of identical twins where one was gay and one straight (which is more common than both being gay). All pairs were puzzled by their eventual differences, which often didn’t emerge until well after puberty. In these genetic clones, genes might explain their increased susceptibility but clearly were not enough to be in any way “deterministic.”

Importantly, while genes couldn’t explain the differences, the relatively new mechanism of epigenetics—which can differ between twins—was the probable reason. When I discussed these results last year on the radio, gay rights activists seemed to get even more upset at the idea of epigenetics rather than plain genetics. They were worried that as these changes were theoretically reversible, epigenetic drugs might become a future anti-gay treatment in oppressive societies.

The complexity and randomness of possible epigenetic changes combined with the biology and multiple influences on sexual preferences make this fear unfounded.

So we could (if someone wanted to pay for it) do a large study of thousands of subjects and find hundreds of “gay genes” of tiny influence, but what would we do with them? As we see from the many identical twin pairs who differ in sexual preferences, they would be useless for prediction. If we found subtle epigenetic changes associated with homosexuality, this would certainly be interesting from a science perspective, but it wouldn’t alter the political debate—although it would certainly guarantee you great publicity for years to come.