My denominational journal, Enrichment Journal, has a wonderful article on the issue of genetic makeup and behavioral determination in general, and on the search for a “homosexual gene” specifically. The article does a wonderful job of dealing with the state of the science on the issue. Though there have been a handful of rather publicized studies done that purportedly show that homosexuality is a genetic (and by strong implication unalterable) trait, none of them have stood up to scrutiny. (The video link gives you more information than the article excerpt.)
There are a couple of very important points that are not often dealt with when the issue of the behavior of homosexuality and genetic make-up are raised. First of all, if we want to morally justify some behavior based on the genetic foundation for that behavior, it is logical to extend our justification then to other behaviors that have a stronger genetic base than the first behavior. For example, there is more evidence connecting certain genetic markers to violent behavior than to homosexuality. If we want to use genes to justify homosexuality, it is reasonable to expect us to justify violent behavior to a greater degree. If I am OK with homosexuality based on the science, then I am really OK with violence.
The fact that most people don’t want to take that logical step—even those with a vested interest in the connection between genes and homosexuality--means the real issue is not about genetic make-up at all. The question of behavior (outside of extraordinary cases of pathology) is irreducibly a moral question.
Genes are not destiny. They may predispose someone to be an abuser given the right environment, but we rightly hold that person to a higher moral standard, and consider them morally responsible for their actions. This moral standard necessitates that we assume the person genetically predisposed to violence has the wherewithal to obey a higher, non-physical law. We expect him or her to overcome genes and environment and obey a moral precept.
Even the language we use to describe this moment of moral decision is revealing. We may colloquially rephrase that last sentence to say, “We expect him or her to disobey genes and environment and obey a moral precept,” but that would be technically false usage. “Disobey” in the first usage is loose in its meaning while “obey” in the second is strict—we equivocated. We cannot obey something that does not give binding orders. Cancer does not order (in a moral sense) cells to reproduce uncontrollably; civil governments do order citizens to not kill each other.
When encountering this very touchy and sensitive issue in the public square, we need to be clear on our moral reasoning. Though there clearly are genetic and environmental predispositions, those do not necessarily predetermine behavior. If they did, moral culpability would be a completely different notion than we rightly hold it to be.