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February 11, 2008

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A function for “gay genes” after all?

Sa­mo­an lovers hint at ev­o­lu­tion­ary mech­a­nisms, sci­en­tists claim

Feb. 8, 2008
Special to World Science  

Stud­ies of some un­usu­al men in the re­mote Pa­cif­ic have led sci­en­tists to sur­pris­ing con­clu­sions about ho­mo­sex­u­al and oth­er gender-bending be­hav­iors.

One of these con­clu­sions: sex­u­al at­trac­tion to mem­bers of the same sex may have an ev­o­lu­tion­ary func­tion, though past stud­ies had failed to find one.

The red ar­row shows the ti­ny is­lands of Sa­moa, sand­wiched in the Pa­ci­fic be­tween the land mass­es of Aus­tral­ia (left) and North Amer­i­ca (right.) (Click for larg­er view). (Im­age cour­te­sy U.S. State Dept.)

Samoan lovers hint at evolutionary mechanisms, scientists claim Studies of some unusual men in the remote Pacific have led some scientists to draw surprising conclusions about homosexual and other gender-bending behaviors. One of these conclusions: sexual attraction to members of the same sex may have an evolutionary function, a finding in conflict with some past studies. A second assertion to emerge from the work is that mainstream psychologists should reconsider the way they classify transsexualism—a strong desire to be the opposite sex—as a disorder. The research focuses on a remarkable group of men who have sex with men, though they defy widespread notions of what a “gay” man is. They form a broadly accepted social class in Samoa, a south Pacific island nation. The studies are directed in part toward resolving a scientific mystery: why does homosexuality persist in the world? Evolutionary theory, the lens through which most scientists study biological traits, holds that in each population, the genes of members who reproduce the most come to dominate the gene pool. That’s because these individuals, unsurprisingly, spread their genes most widely. But by that logic, gays, who reproduce little, shouldn’t exist. What gives? The explanation, many scientists argue, could be that the childless gays put extra efforts into helping raise nephews and nieces. That would boost the children’s chances of survival and, someday, of reproduction. These youths, even if not gay, might carry one or a few of the uncle or aunt’s genes promoting homosexuality—ensuring a clutch of “gay genes” in every generation. The problem with this proposal: it has failed past scientific tests. A few studies found gays weren’t especially helpful to their families. Those findings worked in favor of other scientists who question the whole idea of finding this “evolutionary function.” They say homosexuality is an aberration, so it has about as much biological function as a birth defect does—none. Mainstream physicians no longer consider homosexuality a disorder, but it was only in 1994 dropped from the American Psychiatric Association’s handbook of mental disorders. Transsexualism, or “gender identity disorder,” is still listed, though the manual said it’s only a disorder if it causes the patient significant distress. In the new studies, Canadian psychologists sought to test some of these competing ideas by visiting Samoa, a relatively un-westernized land. By studying people who they said live closer to the ways of humanity’s “ancestral” past, the researchers said they hoped to assess possible evolutionary functions for homosexuality the roles of other gender-blurring behaviors. The kin-selection hypothesis, researchers said, might have failed past tests because these were done in modernized Western societies. Gays might help relatives more in traditional, tribally-based cultures, the scientists said, because these often have tighter-knit families and fewer anti-gay biases that could alienate gays. Moreover, the researchers argued, the traditional environment is more appropriate to study, as it’s more like the setting in which humans mainly evolved. Men who habitually have sex with men are socially accepted in Samoa, where they’re known as fa’afines. Some characteristics of fa’afines, the psychologists said, are quite foreign to Western concepts of homosexuality: notably, they have sex only with men who are considered “straight,” not with each other. But they are Samoa’s equivalent of what Westerners would call gay men. Based on fa’afine responses on questionnaires, compared to responses of heterosexual Samoan men, the researchers concluded that fa’afines put “significantly” more effort into raising nephews and nieces. The childcare activities that saw stronger input from fa’afines included babysitting, buying toys, tutoring, exposing the children to art and music, and contributing to day-care, medical and education expenses, the surveys indicated. It’s the first study to offer real evidence for the Kin Selection Hypothesis’ basic prediction, “that androphilic [“gay”] males should direct more altruistic behavior toward kin than gynephilic [“straight”] males,” the team wrote in a report of their findings. The paper appeared in last May’s issue of the research journal Evolution and Human Behavior. But more studies will be needed, wrote the authors, Paul Vasey and colleagues at the University of Lethbridge in Alberta. A stronger study would compare the fa’afines to childless non-fa’afines, they noted. In their own study, 58 percent of the “straight” respondents had children, who could have diverted their attention from nephews and nieces. In another study, Vasey and Nancy Bartlett of Mount Saint Vincent University in Nova Scotia concluded that psychologists’ assessment of transsexualism as a disorder, at least for children, should be revised. The relationship between transsexualism and homosexuality, if any, is unclear, though some experts say that many boys with “gender identity disorder” become gay. Again citing the fa’afine example, Vasey and Bartlett wrote that fa’afines they interviewed seldom recalled being “distressed” by feeling or acting like a girl in childhood. Most such distress—the researchers concluded based on that and other factors—arises in Western societies because of the stigmatization of such children. The pair’s study appeared in last fall’s issue of the research journal Perspectives in Biology and Medicine. The diagnosis of “gender identity disorder in children,” wrote Vasey and Bartlett, shouldn’t be listed “its current form in future editions” of the American Psychology Association’s handbook, the Diagnostic and Statistical Manual of Mental Disorders. “There is no sound evidence that cross-gender behaviors or identities, per se, cause distress.”