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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.

Click to enlarge

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.)   


A sec­ond as­ser­tion to emerge from the work is that psy­chol­o­gists should re­con­sid­er the way they class­ify as a “dis­order” trans­sex­u­alism—a strong de­sire to be the op­po­site sex.

The re­search fo­cus­es on a re­mark­a­ble group of men who have sex with men, though they de­fy much con­ven­tion­al wis­dom on what be­ing “gay” 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? It seems to make lit­tle evo­lu­tionary sense.

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. 

By that logic gays, who re­pro­duce lit­tle, should­n’t ex­ist. Yet they do, along with some evi­dence their ten­den­cies may have a ge­ne­tic component. 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 re­pro­duc­tion. These youths, even if not gay, might share with their aunt or un­cle a few genes pro­mot­ing ho­mo­sex­u­al­ity—en­sur­ing a clutch of “gay genes” in eve­ry genera­t­ion.

One prob­lem with this pro­pos­al: it has failed past sci­en­tif­ic tests. A few stud­ies have found gays aren’t es­pe­cially help­ful to their fam­i­lies. Those re­sults have worked in fa­vor of an op­pos­ing ar­gu­ment, that ho­mo­sex­u­al­ity has no ev­o­lu­tion­ary func­tion. Sci­ent­ists who back this view say ho­mo­sex­u­al­ity is an aberra­t­ion, so it has about as much bi­o­log­i­cal func­tion as a birth de­fect—none.

Main­stream physi­cians no long­er con­sid­er ho­mo­sex­u­al­ity a dis­or­der; it was dropped from the Amer­i­can Psy­chi­at­ric As­socia­t­ion’s hand­book of men­tal dis­or­ders in the 1970s. Trans­sex­u­al­ism, or “gen­der ident­ity dis­or­der,” is still list­ed, though the ma­nual says 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 and the roles of oth­er gen­der-blur­ring be­hav­iors.

The idea about gays helping their kin, called the kin-selection hy­poth­e­sis, might have failed past tests be­cause these were done in mod­ern­ized West­ern so­ci­eties, the re­search­ers said. Gays might help rel­a­tives more in tra­di­tion­al, tribally-based cul­tures, the sci­en­tists claimed, 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 might 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.

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.  

Thus, the researchers wrote, the di­ag­no­sis of “gen­der ident­ity dis­or­der in chil­dren” should no longer be list­ed “in its cur­rent form” in the Amer­i­can Psy­chol­o­gy As­socia­t­ion’s hand­book, the Di­ag­nos­tic and Sta­tis­ti­cal Man­u­al of Men­tal Dis­or­ders. Some gay acti­vists have called for the con­di­tion to be de-listed com­plete­ly. Vasey and Bart­lett didn’t go that far. But in their study, in last fall’s is­sue of the re­search jour­nal Per­spec­tives in Bi­ol­o­gy and Med­i­cine, they did write: “There is no sound ev­i­dence that cross-gender be­hav­iors or ident­i­ties, per se, cause dis­tress.”


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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.”