New Study Disputes 'Gay Gene,' But Doesn't Separate Sex From Identity

The largest-ever study of genes and human sexuality has just been published in the prestigious peer-reviewed journal Science, and the results will inevitably cause a stir. Does the failure of the researchers to find a single "gay gene" mean that being gay or lesbian is a choice, or just that it's complicated? What makes males and females so different? And why are scientists still studying this anyways?

As it turns out, the study can't fully address any of these important issues because of limitations in the way it was designed and executed. But it does quite definitively answer a different question of interest: Does having sex one time with somebody of the same sex mean you're queer?

The answer is no. In fact, the new work provides the first evidence that there are fundamental, differences between individuals with different extents of same-sex experience, and suggests that openness to experience and adventurous behavior are a key elements in the many-layered complexity of human sexuality.

The new study, carried out by 21 authors at as many different institutions, analyzed nearly half a million men and women aged 40-69 in the United Kingdom. Although detailed sexuality information was not collected, the participants were asked the question "Have you ever had sexual intercourse (vaginal, oral or anal) with someone of the same sex?" About 3 percent answered yes, and were classified as "non-heterosexual."

This was the group used for gene hunting, but does this binary measure accurately gauge sexual orientation? From the authors' own data, probably not.

First, there was a remarkably strong dependence on the age of the participants, with people age 40 more than three-times as likely as those age 69 to be classified as non-heterosexual. This sort of rapid temporal change is characteristic of a trait mediated by social factors, not genes.

Second, over half of the "non-heterosexuals" for which data was available actually had sex mostly or at least half the time with the opposite sex. In other words they were mostly straight or bisexual, not gay or lesbian as those terms are commonly understood.

The study got more interesting when the scientists analyzed genetic correlations of "non-heterosexuality" to other behavioral and psychological traits. Two were were especially notable: risk behavior and openness to experience. This does not fit with the typical personality profiles of either gay men or lesbians, which have been studied extensively. Rather, it is what one might expect for individuals willing to do something a bit out of the usual for a change, even if it didn't match their underlying desires or attraction. (There was also a strong correlation to cannabis use. Of course we've all heard that story: "Yes, I did, but I was soooo high.")

The proof of a difference between a one-time same-sex experience and enduring sexual orientation came from examining the genetic relationships between non-heterosexuality and percentage of same-sex partners for participants for whom both measures were available. The correlation was insignificant - zero - nada. What this means is that whatever genes were found for "non-heterosexuality" have nothing to do with the continuum of behavior from "mostly straight" to "completely queer."

In a nutshell, "ever" is as different from "all the time" as it is from "never."

The scientists also searched through 600,000 DNA markers in the sample. As is typical for this type of molecular fishing expedition, thousands of candidate genes were found, five of which were deemed statistically significant. While some are located in potentially interesting genes, such as sex hormones and olfaction, they only accounted for a few percent of total variation and could not predict a person's orientation with any accuracy.

I was not surprised, and indeed somewhat relieved, that no correlation was found with Xq28, the sex chromosome locus linked to male homosexuality that my lab discovered in 1993 and has been independently confirmed. Our work used genetically-loaded families with two gay brothers, as compared to random individuals, focused on predominantly or exclusively gay men, as compared to a population mostly heterosexual or bisexual, and took into account epigenetic influences. If Xq28 had been picked up in the new scan, it could be interpreted as meaning that we had discovered a locus for risk taking, not homosexuality.

Whatever its limitations, I'm delighted that the new study was conducted. There is strong emperical evidence that knowing the origins of sexual orientation leads to increased acceptance, and has played a role in the gradual improvement of our civil and human rights. And yet in the 26 years since our first genetics study appeared in Science, there have been fewer than half a dozen credible research projects on this topic. Antigay forces work in many different ways, and restricting research is definitely one of them.

My one concern is that the work will be misinterpreted. All along, we and the entire scientific community have understood that the genetic architecture of human sexuality is complex, and that there is no single "gay gene." That was always a straw man invented by antigay critics.

But it's easy to confuse "no single gay gene" with "no genetic influence," which in short order will be misinterpreted as "it's a choice." Nothing could be further from the truth, and it's important to stress that just because our sexuality is complex and individualistic doesn't mean that it isn't deeply ingrained as part of our identity.

There is one more tidbit from the new study that may make the whole concept of "gay genes" obsolete, and that is the observation of a genetic correlation between "non-heterosexuality" and total sexual partner number. Perhaps you are rolling your eyes at what would seem to be yet another confirmation of our loose morals, but hold on; a genetic correlation means that straight people who share our genes -- and there are a lot of them -- also have more sexual partners. That would solve the conundrum of how "gay genes" survive evolution. It's because they are really "hyper-heterosexuality genes" -- and probably essential for the survival of the human race.

Dean Hamer, PhD, is Scientist Emeritus at the National Institutes of Health. Cited Paper: Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior. Andrea Ganna, Karin J. H. Verweij, Michel G. Nivard, Robert Maier,Robbee Wedow, Alexander S. Busch, Abdel Abdellaoui, Shengru Guo, J. Fah Sathirapongsasuti, 23andMe Research Team, Paul Lichtenstein, Sebastian Lundstrom, Niklas Langstrom, Adam Auton, Kathleen Mullan Harris, W. Beecham, Eden R. Martin, Alan R. Sanders, John R. B. Perry,Benjamin M. Neale, Brendan P. Zietsch