Just recently, the largest twin study to date examining genes’ influence on homosexuality was published in the journal Psychological Medicine. The study involved 409 pairs of homosexual brothers. Genome-wide analyses showed strong evidence, the researchers claimed, that two chromosomes, X and chromosome 8, mediated homosexuality based on the genes they shared.

For some experts, particularly those involved with the work, the findings had “landmark” written all over them. But for those less optimistic, the study was flimsy and statistically mediocre, if outright insignificant. Even Dr. Alan Sanders, a behavioral genetics researcher at NorthShore University HealthSystem Research Institute and the study’s lead author, said the evidence “is not proof, but it’s a pretty good indication” that genes wield some influence on sexuality.

Missing the Mark

Clearly, the controversy exists. For as long as scientists have had access to people’s genes, they’ve tested the idea that who we’re attracted to is written into our DNA — some so-called “gay gene” exists, and if only we look hard enough we will find it. But this raises startling questions about which scientific findings matter the most to us, particularly as our knowledge of the brain grows in parallel to our known ignorance of its power.

The brain isn’t a painting that scientists can walk around in. It’s a hurricane, where things are constantly swirling in flux. And sexuality, for that matter, is just as turbulent. The terms we use to describe certain urges — “gay,” “straight,” or some other shade of gray in between — don’t exist in nature. We made them up. According to Brian Earp, of the University of Oxford Uehiro Centre for Practical Ethics, the best science can do to trace sexuality’s origins is get kind of close.

“It can say, ‘Given this sort of genetic information it turns out that this leads to this sort of probability that the person will consciously experience these kinds of sexual attractions,” Earp told Medical Daily.

What it can’t say is, here is this chromosome and it’s the gay chromosome, and we know this because a large number of gay men all share this gene. The model unhelpfully leaves out entire swaths of personal life experience dealing with social interactions, upbringing, environmental factors like political climates and geography, and, indeed, other genes.

This is why the “Born this way” argument tends to fall apart for Earp. As a cognitive scientist, he freely admits the field of sexuality research doesn’t have all the answers for why certain people like men or women, both or neither. Sexuality falls on a spectrum, and brain chemistry is too complex for a person’s feelings of attractions to be reduced to a puny set of chromosomes. The “Born this way” argument is weak because it breaks the cardinal rule of scientific inquiry by removing all room for doubt.

The Stronger Argument

If by some scientific breakthrough involving key hormone levels or other chemical changes, “it turns out later that you can choose,” Earp said, “then you’re going to lose your moral grounding” for advocating against discrimination on the basis of sexuality. “The argument needs to shift elsewhere.”

The alternative is plain to see: All sexualities are fair. Sexuality as a component of rigid personhood is nice from a political standpoint, in other words, but it gives skeptics too much room to exploit any scientific breakthroughs to their advantage.

Ultimately, the search for a “gay gene” is just another player complicit in that argument, and perhaps a dangerous one if the research proceeds far enough. In cellular models, for instance, scientists have already found genetic on-off switches for things like cancer, aging, and certain autoimmune diseases. The field of epigenetics devotes great resources to targeting these abnormalities, and locating a “gay gene” would only legitimize sexuality as something to be studied in a lab, rather than a social and biological phenomenon as clinically uninteresting as hair color or height.

Correction: A previous version of this article incorrectly attributed the twin study to the journal Psychological Science. It was published in Psychological Medicine.