About once a day I get an e-mail message from some group urging me to take a position--pro or con, usually con--in the controversy over gay marriage, the most hotly debated social issue of the moment.
The issue highlights the value of approaching questions related to human nature from a perspective combining both scientific and religious insights. Much of the recent work in science-and-religion, for example, has revolved around evolutionary psychology, which studies human behaviors in light of our evolutionary past.
The central insight of evolution is that natural selection works to get one's genes into the next generation. Recent developments have provided compelling evidence that natural selection works on behaviors, as well as physical traits.
Behaviors that seem counter to reproductive fitness, like altruism or homosexuality, pose problems for the most simplistic of evolutionary models. How, for example, can there be a genetic basis for helping others at the expense of one's self-interest? Or sexual preferences that don't result in offspring? Sophisticated evolutionary models, such as those used in evolutionary psychology, have shown, however, that natural selection can result in behaviors that don't benefit individuals, if they benefit their relatives. Parents of virtually all species, for example, happily, or at least instinctively, sacrifice their self-interest for the interest of their children. But children carry their parents' genes into the next generation, so it is easy to see how natural selection would favor parents who act this way. Parental love and care is thus thought to have a strong genetic basis, although the genetic details are yet to be worked out.
Evolutionary psychology also sheds light on the phenomenon known as homophobia. Human beings, with frightening ease, divide other human beings into in-groups and out-groups. We perceive "our" group as "ins," the modern analog of ancient tribes' extended families that shared our genes. The "outs" are those we perceive as different from us. These instincts--alas, all too natural--lead us to tease the fat classmate, reject the immigrant, overlook the homeless man and marginalize the gay neighbor.
Considerations such as these suggest that both homosexuality and homophobia may have genetic origins. Evidence for a "gay gene" appeared a few years ago, giving rise to an argument that if homosexuality had a genetic basis, then it was "natural" and thus should not be opposed.
At this point, however, serious moral reflection must kick in. Genetically based behaviors are indeed "natural," in the sense that they grow out of our human nature. Such behaviors cannot be rejected as immoral using the argument that they are perversions of our natures or mental disorders. On the other hand, establishing that behaviors have a genetic basis hardly constitutes an argument that such behaviors are to be either embraced or condoned. One cannot reason so simply from "is" to "ought" or "ought not." There is something strange about promoting homosexuality with an argument that also promotes homophobia.
Such questions are difficult and deep. They challenge our science, our religion and our wisdom. There is much we don't yet know that we need to know. But one thing seems clear: The questions are much more complex than the lobbyists spamming us with e-mails seem to realize.