By Timothy F. Murphy

In written English, words are read from left to right, while Arabic words are read from right to left. In Japanese, the written language is read from the top to the bottom of the page, in columns that read from right to left. We normally see these variations as nothing more than a custom and don't go looking for biological explanations. Yet when men have sex with other men, and women have sex with other women, we are tempted to think that there must be more to the behavior than custom or simple choice alone. Since the late 1800s, friends and foes of homosexuality alike have tried to identify biological reasons why some people are homosexual. The German psychologist Richard von Krafft-Ebing (1840-1902) was among the first to speculate that some people - but not all - might be homosexual for genetic reasons. Since that time, many explanations of homosexuality have come and gone, especially psychological theories, but some researchers still look to genetics as an explanatory tool that can prevail where other explanations have failed.

But why do we care about the genetics of homosexuality at all? Since the early 1990s, biologist Ruth Hubbard has cautioned that this interest was driven by moral disapproval. How else to explain the overwhelming interest in this aspect of human sexuality but the yawning lack of interest in other dimensions of sexual behavior? One way to see how cultural standards play a role in scientific inquiry is to consider that most of the studies of homosexuality have looked at males, not females. What accounts for this imbalance? Is it the idea that the loss of anything to a male is always more important than the loss of the same thing to a female, heterosexuality included? Even if that's not the reason, it's hard to escape the conclusion that cultural worry has driven scientific interest in homosexuality, and not just innocent curiosity. It was no accident that many of the early studies of homosexuality were also looking for treatments and cures.

In part, cultural critics of sexual science have it right. Heterosexuality is so profoundly pervasive in human culture that it skews the very perception of homosexuality. Against a social background deeply saturated with sex between men and women, sex between men and sex between women looks unusual in a way that seems to demand explanation. This perception persists despite the fact that homosexuality is never far from the surface of most cultures. Across human history, both men and women have taken sexual partners of their own sex. Even so, we rarely think of homosexuality as emblematic of human nature itself, as something beyond the need for explanation.

The cultural motives that have spurred interest in the 'causes' of homosexuality have ironically thrown up cultural roadblocks to its study. For one thing, people are reluctant to disclose their homosexual behavior and interests if doing so puts them at risk of social mistreatment and stigmatization. Even when people are willing to be frank with researchers, the lines separating 'homosexuality' from 'heterosexuality' can be blurry. The Kinsey studies of 1948 and 1953 were the first to make a serious attempt at estimating the extent of homosexuality in the United States. These researchers quickly discovered that some people never engage in same-sex erotic behavior, some people never engage in opposite-sex behavior, while some men and women engage in same-sex erotic behavior for certain periods of times. Later studies conducted by sociologist Edward O. Laumann and his colleagues reported similar sorting difficulties, as they concluded that that approximately 2.8% of their overall male subjects and 1.4% of their overall female subjects identified themselves as having a homosexual or bisexual identity, while more people living in urban centers did so. But even some of these people had heterosexual sex, not to mention the much larger number of people who have had homosexual sex at some point without claiming a homosexual or bisexual identity. On this spectrum, who is 'homosexual' and who is not? Should researchers use a 'one drop' approach: anybody who engages in sexual activity with someone of the same sex is homosexual in some degree? Cultural habits of treating people as either homosexual or heterosexual may impose more sexual specificity than actually exists in human behavior. Even so, what some critics of genetic research of homosexuality don't get entirely right, I think, is that questions about the development of sexuality are amenable to scientific study even if cultural influences play a role. It is certainly meaningful to ask how - out of all possible sexual interests human beings can have - people come to the actual interests they have, and the answer to this question can incorporate cultural influences into pathways of sexual development as necessary.

Some people do not like biogenetic studies of sexual orientation not because they think it is conceptually confused but because it undercuts their cultural authority. In 2000, the Catholic Medical Association took pains to repudiate the idea that homosexuality could be genetic. Their statement, titled 'Homosexuality and Hope,' virtually says that homosexuals as such don't exist, only men, women, and adolescents in states of psychological conflict. But if some people are homosexually oriented for genetic reasons or any other reasons rooted in biology, that account fails as an explanation, and the Association's 'hope' of rescuing homosexual people from their confusion would falter. The North American Association for Reparative Homosexuality is no fan of sexual orientation genetics either. This group's denial that homosexuality is genetic enables them to champion their explanations of homosexuality; for example, they think male homosexuals suffer a psychic injury at the hands of their fathers as children. Genetic reasons for homosexuality would dissolve this explanation, and the 'therapies' that it authorizes.

By marked contrast to critics who deny a biogenetic basis for homosexuality, some gay men and lesbians welcome those kinds of explanations precisely because they shore up their identities. Homosexuality that is hard-wired - that is a genetic effect, for example - is homosexuality that doesn't lend itself to labels of psychological maladaptation or moral lapse. Genetic and other biological theories seem to read homosexuality into nature alongside heterosexuality, and some gay men and lesbians embrace those biogenetic accounts for that protective effect. They understand biological explanations as sympathetic to their own 'creation narratives' of who they are and how they come to be.

The benefits of genetic explanations for sexual identities do, however, come with a cost. An identified biogenetic trait for homosexuality might open the door to testing and treatment for adults, adolescents, children, and fetuses alike. In the worst case scenarios, some women might abort fetuses they believed likely to become homosexual children, and some adults and adolescents might be subjected to involuntary testing and treatment. When publishing their 1994 linkage study of male homosexuality, geneticist Dean Hamer and his colleagues took the highly unusual step of directly addressing these kinds of downstream effects of their work. At the end of their report in the journal Science, these researchers said: “We believe that it would be fundamentally unethical to use such information [about genetic linkages] to try to assess or alter a person's current or future sexual orientation, either heterosexual or homosexual, or other normal attributes of human behavior. Rather, scientists, educators, policy-makers, and the public should work together to ensure that such research is used to benefit all members of society.” Other researchers have disputed the findings of the Hamer laboratory's 1994 report that male homosexuality is linked to a section of the X chromosome, and no study has ever offered direct evidence for a comparable linkage in lesbians. Even so, genetic and biological studies of homosexuality continue to come along, and the debate about their effect on the future of gay men and lesbians continues.

In this debate, some researchers and commentators overvalue the role biogenetic explanations of homosexuality can play in shaping favorable public attitudes toward homosexuality. No amount of genetics is likely to prevail against philosophical views that homosexuality is unnatural because of the inherent sterility of same-sex relationships, and genetics will not help at all with outright bigotry. By the same token, critics of this research tend to overstate the damage that research like this could do. The U.S. Supreme Court managed to strike down sodomy laws as unconstitutional, and some states have legalized same-sex marriage, no matter that biological studies of homosexuality in humans and animals have continued without a lull in the past two decades.

I plead agnostic to knowing whether or not homosexuality comes hard-wired in for some people, though some evidence seems to suggest as much. While only more research can answer that question definitively, sexual science would be lazy in the extreme if all we wanted to know is the biology of homosexuality and not the full array of human sexual interests and not either what role culture plays in the panoply of human sexual diversity. In the meantime, how do we understand the nature of gay and lesbian identities? There is no uniform answer to this question. In the absence of definitive explanations of homosexuality, some commentators try to de-legitimize those identities entirely. Yet other commentators welcome these studies - tentative though they might be - as a shield against hostile views that homosexuality is a psychological or moral failing. Other commentators worry that definitive explanations of homosexuality would empower tools to be used against gay men and lesbians. Conflicting views about the value of this science are possible because there is no single social meaning of science. So long as an interpretation of genetics does not contradict the observable facts, commentators are free to offer their interpretations about its meaning and value, the original intent of the investigators notwithstanding.

Ultimately, the value of gay and lesbian identities rests primarily with what they mean to the people who accept them and who identify themselves that way. Against the pervasive influence of heterosexual culture, one value of these identities lies in their oppositional effect in undercutting the presumption that men and women are only ever sexually attracted to one another and that society at large may proceed blithely in matters of law, religion, and culture as if there were no same-sex attraction and relationships. We don't need a specific biological grounding for political identities that work toward a better life for gay men and lesbians, but we also shouldn't condemn this science as conceptually impossible or prejudicial by its very nature.

Timothy F. Murphy holds a doctorate in philosophy from Boston College and is Professor of Philosophy in the Biomedical Sciences at the University of Illinois College of Medicine at Chicago. He is the author of Gay Science: The Ethics of Sexual Orientation Research (Columbia University Press) and is writing a book called Parents' Choices and the Future of Gay Men and Lesbians.

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