Is There a “Gay Gene"?

Not long ago, I had a conversation with a Methodist minister who was lamenting the recent schism in the once “United" Methodist Church. He explained that this split had come about over a disagreement about whether to accept LGBTQ persons into their congregations.

“So, is there really a gay gene?” he asked.

“Well, yes, sort of,” I replied. “But it’s complicated.”

As University of Toronto (Canada) psychologist Doug VanderLaan and his colleagues explain in an article they recently published in the journal Archives of Sexual Behavior, science now clearly shows that people are born with their sexual orientation. Many people assume that if a trait is something we're “born with,” it must be genetic—but in fact, it’s not that simple.

On the one hand, traits can be determined by multiple genes, such that a single trait may have any number of genetic causes. On the other hand, the way we come out of the womb is determined as much by conditions inside the womb as they are by our genes. That is, the presence of particular hormones during prenatal development, as well as the reactions of our mother’s immune system, can have a big influence in shaping who we are.

Sex, Sexual Orientation, and Gender Expression

The fact that there are many different prenatal events that can lead a person to have a same-sex orientation as an adult is an important aspect of the theory that VanderLaan and colleagues lay out in their article. But even more compelling is their argument that these different ways of becoming gay also lead to different ways of being gay.

To understand VanderLaan and colleagues’ approach, we first need to define three key concepts and related terms. The first key concept is sex, which is generally used in psychology to refer to the biological aspects of being a male or female. These include not only the obvious sex characteristics of the body but also less-observable traits such as the relative length of certain bones and specific brain structures, which can also be used to distinguish biological males from females.

The second key concept is sexual orientation, that is, which sex you are attracted to. According to VanderLaan and colleagues, a distinction between opposite-sex and same-sex attraction is too simplistic. That’s because the developmental events that lead a man to feel attracted to other men are different from those that lead a woman to feel attracted to other women. In other words, certain factors lead some individuals to be attracted to males and others to females, regardless of whether they themselves are male or female.

The third key concept is gender expression. This is related to the concept of gender identity, but it focuses on outwardly observable behaviors as opposed to inner cognitions and emotions. Gender expression has to do with the socially acceptable ways of behaving that are ascribed to males and females. Whenever we have social rules saying that men should act one way and women another, we’re talking about gender expression.

It’s important to point out that gender expression is unrelated to both sex and sexual orientation. For instance, the common assumption that all gay men are effeminate is simply wrong. Some do express feminine gender characteristics, while others act in ways that are quite masculine, even hyper-masculine.

Genes, Hormones, and the Mother’s Immune System

The science clearly shows that genes play a role in determining sexual orientation. Family studies indicate that homosexuality clusters in some families but not in others. Likewise, twin studies suggest that identical twins are more likely to have the same sexual orientation than fraternal twins. These results can only be explained in terms of genetics, but they don’t provide the full answer.

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The presence or absence of male and female sex hormones during fetal development plays an important role as well. For instance, we know that males who were exposed to female sex hormones such as estrogen or progesterone during prenatal development are more likely to have a same-sex orientation as adults. The same is true for female fetuses that were exposed to the male sex hormone testosterone. In other words, exposure to particular hormones in the womb influences the sex we’re attracted to as adults.

The mother’s immune system can also get involved. In what is known as the fraternal birth order effect, first-born males are less likely to exhibit a same-sex orientation than males who are born after an older brother. It’s believed that the mother’s immune system becomes sensitive to male hormones during the first pregnancy, which then sets out to neutralize these during subsequent male pregnancies.

Different Ways of Being Gay

Gay men often categorize themselves into what they call “tops” and “bottoms” (it's also possible to be a "switch"). Broadly, tops are the penetrative partner in anal sex, while bottoms are the receptive partner. Later-born males are more likely than first-borns to be gay, but only as bottoms, not as tops.

Other evidence suggests that tops tend to be hyper-masculinized. That is, they tend to display various male characteristics that are even more extreme than heterosexual males. In other words, this pattern of results would appear to place gay men at the two extremes of the “masculine” scale, with heterosexual males occupying the middle ground, “bottoms” at the lower end, and “tops” at the higher end. Apparently, then, both sexual orientation and gender expression in males can be influenced by conditions in the womb during prenatal development.

The data also point to a similar pattern in women. Again, the stereotype of lesbians as masculine women is simply false. Rather, women with a same-sex orientation frequently categorize themselves as “femmes” or “butches.” Femmes act in more stereotypic feminine manners, while butches exhibit more masculine behaviors. Likewise, femmes tend to exhibit more typical female physical characteristics, while butches tend to have more male features.

In sum, these data suggest that asking whether there’s a “gay gene” isn’t the right way to think about the issue. Both genes and conditions in the womb shape the multiple ways that people experience their biological sex, the people they’re attracted to, and the way they feel about their gender.