Stud­ies of homosexual men in the re­mote Pa­cif­ic have led sci­en­tists believe that ho­mo­sex­u­ality and oth­er gender-queer be­hav­iors may have an ev­o­lu­tion­ary func­tion World Science has reported.

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.

It’s the first study to of­fer real ev­i­dence for the kin se­lec­tion hy­poth­e­sis’ bas­ic pre­dic­tion, “that gay males should di­rect more al­tru­is­tic be­hav­ior to­ward kin than s­traight males.

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 homosexuals 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, 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 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.”

Tags: gay evolution, gay gene, gay men, gay parents