Are people born gay? Before we attempt to answer this question, we need to unpack it. We will find a) that the question itself is flawed in the sense that it presupposes an outdated and incorrect causal view of heredity, b) the term "gay" can be redefined based on one's political views, c) there are flawed implications involved, and d) the science is often misunderstood.
The question is predicated on a simplistic view of causality. No more than 20 years ago a "hot debate" among academics was the idea of "Nature vs. Nurture," the "blank slate," and other similar false dichotomies that suggest, if not directly stated, that behavioral (how we act), cognitive (how we think), or affective (how we feel) traits are either a result of biological factors (e.g., hormonal, genetics, in utero) or environmental factors (e.g., parental guidance, diet and exercise, social bonds). Today, with the recent advances in the study of genetics, human traits are understood to be a complex interaction between both biology and environment. For example, even height, a clearly physical trait, is said to be only about 90% heritable. The other 10% is due to environmental factors such as diet. The discussions in science today about heritability don't focus on causes; they focus on how much influence each biological and environmental factor has on the trait. To answer yes to the question "Are people born gay" we would have to ignore the environmental influences, taking us back to the "Nature vs. Nurture" false dichotomy.
The term "gay" can refer to a label with which one identifies, a person who has sexual or romantic feelings for another person of the same sex, or a person who engages in sexual activity with a person of the same sex. This issue gets even more complex when we stop incorrectly seeing homosexuality as a black and white issue and realize that all the uses of the term "gay" exist on a spectrum. For example, there are many people who are bisexual, but on the heterosexual end of the spectrum, who may occasionally engage in sexual activity with a person of the same sex, yet not refer to themselves as "gay." There are also many people who engage in heterosexual behavior but have strong sexual or romantic feelings for another person of the same sex and do not refer to themselves as "gay" perhaps for religious or social reasons. By playing with these terms, we can have two very different arguments: the claim that being born gay means that one is biologically determined to either have gay sex or be attracted to people of the same sex.
Again, a naive view of causality might suggest that being born a certain way means 100% determined, and not being born a certain way means 100% choice. As usual, reality is far more complex. Without getting into the issue of freewill, we can say that both biology and environment influence who we are. Biological influences are not inherently more powerful than environmental ones when it comes to limiting our level of control or choice——the strength of the influence is independent of its source.
While it's certainly not unreasonable to suggest that one has a choice in which label they identify with or to engage in sexual behavior; it's unreasonable to suggest that one can choose to whom they are attracted. We can choose to talk to someone who we find unattractive, but that doesn't mean we can choose to make ourselves be attracted to that person. There are biological and environmental influences not present at our births that regulate our choices based on how we feel about things. Not being born attracted to Elsa, the sweet 84-year-old woman next door, is not the same as choosing not to be attracted to Elsa. It could simply be that you don't find Elsa attractive, and no conscious and deliberate effort will change that, regardless of the percentage of biological and/or environmental influences that resulted in the lack of attraction.
In a complex trait such as homosexuality, we are almost certainly talking about a combination of many genes (not a single "gay gene") that interact with the environment, so different environments are more conducive to the expression of certain genes. Back to our earlier example, genes that code for height will not be fully expressed with an inadequate diet. Now with decades of data from twin studies on homosexuality backed by empirical studies looking at other biological influences such as chromosome linkage, birth order, female fertility, pheromones, and brain structure, it is very clear that homosexuality is significantly biologically influenced (for a fairly easy read on this, see this Wikipedia page). In the case of twins studies, homosexuality is significantly more common among identical twins (i.e., siblings with the same genes) than in fraternal twins (i.e., siblings who share 50% of genes) (Michael, Dunne, & Martin, 2000). Without quibbling over exact numbers, let's say that the heritability of homosexuality is about .15 or 15%. This means that, on average, if one identical twin is gay the other twin has a 15% chance of being gay, compared to the (very rough) estimate of 5% in the general population. Heredity is a term used when talking about averages within groups and cannot be used when talking about an individual. This means that in any given case, a twin could have a 0% chance of being gay, a 100% chance, or anywhere in between. We just don't know. Think of a glass of Diet Coke and a glass of water. Both will sit there relatively inactive, however, if there were a 15% chance a kid would walk by and throw Mentos in both drinks, the Diet Coke would explode (see demonstration) and the water would not. There isn't a 15% chance that the Diet Coke would explode if the kid threw Mentos in it; it is a close to a 100% chance. Likewise, just because we calculate a trait to be 15% heritable, that does not mean that if certain environmental forces act on the genes that there is a 15% chance it will result in the expression of the genes. Given certain environmental forces, expression of the genes might be inevitable. For this reason, we cannot conclude that some people are not determined to be gay from birth. Again, we just don't know.
We can say that people are born male or female because these are objective and unambiguous criteria identifiable at the time of birth. However, when it comes to identifying a feeling such as sexual attraction, the best we can do is claim that some people do appear to be born with predispositions to same-sex attraction, which is not the same as being born gay. While "baby, I was born this way" might make a catchy song lyric, it makes a lousy argument.
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