What do the new ‘gay gen’ tell about sexual orientatn? | New Scientist

Contents:

• WHAT DO THE NEW ‘GAY GEN’ TELL ABOUT SEXUAL ORIENTATN?
• THERE IS NO ‘GAY GENE.’ THERE IS NO ‘STRAIGHT GENE.’ SEXUALY IS JT PLEX, STUDY NFIRMS
• WHY ARE PEOPLE GAY? GAY BY CHOICE OR IS BEG GAY GEIC?
• NO ‘GAY GENE’: MASSIVE STUDY HOM ON GEIC BASIS OF HUMAN SEXUALY
• THE LIFE OF THE GAY GENE: OM HYPOTHETIL GEIC MARKER TO SOCIAL REALY
• THE REAL STORY ON GAY GEN
• SEARCH FOR 'GAY GEN' COM UP SHORT IN LARGE NEW STUDY
• NEWS: 'GAY GEN': SCIENCE IS ON THE RIGHT... (THE GUARDIAN) - BEHD THE HEADL
• GAY GEICSMOST OF BELIEVE THAT WE WERE BORN THAT WAY, BUT IS SEXUAL ORIENTATN OUR DNA? JV CHAMARY GO SEARCH OF THE GAY GENEJV CHAMARYPUBLISHED: MAY 31, 2009 AT 11:00 PMGAY GEICS
• THERE’S (STILL) NO GAY GENE
• THE 'GAY GENE' IS A TOTAL MYTH, MASSIVE STUDY CONCLUS
• THERE’S NO ONE ‘GAY GENE,’ BUT GEICS ARE LKED TO SAME-SEX BEHAVR, NEW STUDY SAYS
• IS THERE A “GAY GENE"?
• GAY GENEALOGY AND GAY FAY HISTORY INFORMATN
• MANY GEN INFLUENCE SAME-SEX SEXUALY, NOT A SGLE ‘GAY GENE’

WHAT DO THE NEW ‘GAY GEN’ TELL ABOUT SEXUAL ORIENTATN?

In 1993, geic variatns a regn on the X chromosome men were lked to whether they were heterosexual or homosexual, and 1995, a regn on chromosome 8 was intified. Grave’s disease is more mon gay than straight men, and some rearch suggts that gay men tend to be thner – which might possibly be a rult of thyroid overdrive.

The latt fdgs open the prospect to intifyg the whole pathway of gen volved both homosexual and heterosexual orientatn, says Dean Hamer at the US Natnal Instut of Health, who led the study that ppoted chromosome X back 1993.

THERE IS NO ‘GAY GENE.’ THERE IS NO ‘STRAIGHT GENE.’ SEXUALY IS JT PLEX, STUDY NFIRMS

In theory, humans and other animals who are exclively attracted to others of the same sex should be unlikely to produce many blogil children, so any gen that predispose people to homosexualy would rarely be passed on to future generatns. Yet same-sex attractn is wispread humans, and rearch suggts that is partly a study of data om hundreds of thoands of people, rearchers have now intified geic patterns that uld be associated wh homosexual behavur, and showed how the might also help people to fd different-sex mat, and reproduce.

The thors say their fdgs, published on 23 Augt Nature Human Behavur1, uld help to expla why gen that predispose people to homosexualy ntue to be passed down.

WHY ARE PEOPLE GAY? GAY BY CHOICE OR IS BEG GAY GEIC?

Most of the participants were born durg a time when homosexualy was eher illegal or culturally taboo their untri, so many people who were attracted to others of the same sex might never have actually acted on their attractn, and uld therefore have end up the wrong group the Monk, an elogist and evolutnary blogist at Yale Universy New Haven, Connecticut, thks that the veats are so important that the paper n’t draw any real nclns about geics and sexual orientatn.

Instead, he thks the rearchers have found geic markers associated wh openns to new experienc, which uld expla the overlap between people who have had a homosexual partner and heterosexual people who have had many partners. Humans have tried to unrstand human sexualy for centuri — and geics rearchers joed the ay the early 1990s after a seri of studi on tws suggted homosexualy ran fai. “As a teenager tryg to unrstand myself and unrstand my sexualy, I looked at the ter for “the gay gene” and obvly me across Xq28, ” said Fah Sathirapongsasuti, a study -thor and senr scientist at 23andMe, which he joked once led him to believe he hered his gayns om his mother.

NO ‘GAY GENE’: MASSIVE STUDY HOM ON GEIC BASIS OF HUMAN SEXUALY

The rearchers had members of the same-sex muny review the study’s sign and language, and they adm that their termology and fns for gay, lbian and heterosexual do not reflect the full nature of the sexualy ntuum.

“[Our study] unrsr an important role for the environment shapg human sexual behavr and perhaps most importantly there is no sgle gay gene but rather the ntributn of many small geic effects sttered across the genome, ” Neale said. Those who nsir beg gay a disadvantage life (which still is, certa societi), might regard gay people differently if they knew that beg gay was an hered tra, rather than a nsequence of life events, such as a particular type of upbrgg, or mixg wh certa sorts of iends or even a liberate cisn.

THE LIFE OF THE GAY GENE: OM HYPOTHETIL GEIC MARKER TO SOCIAL REALY

An early study claimed that if one pair of (male) intil tws (who have intil geic patterns) was gay, there was a 100 percent chance of the other one also beg gay. It was quickly shown that, fact, the real chance of two intil tws beg gay was around 40-50 percent, whereas was ls non-intil on, though still somewhat greater than the general populatn. There was another, much smaller, group who said they were entirely gay (about 6 percent), and a stterg of even smaller numbers who claimed to be bisexual.

THE REAL STORY ON GAY GEN

It very much appears that same-sex sexual attractn is not a choice but actg on is; so if you fe gay as the mere prence of same-sex attractn, then om everythg we unrstand, beg gay is not a choice.

If, on the other hand, you nsir someone to be gay only if they act on their same-sex attractn then beg gay n be nsired a choice pendg on an dividual's behavr. “There is no ‘gay gene’, ” says lead study thor Andrea Ganna, a geicist at the Broad Instute of MIT and Harvard Cambridge, and his lleagu also ed the analysis to timate that up to 25% of sexual behavur n be explaed by geics, wh the rt fluenced by environmental and cultural factors — a figure siar to the fdgs of smaller studi. However, blogists have documented homosexual behavr more than 450 speci, argug that same-sex behavr is not an unnatural choice, and may fact play a val role wh populatns.

So-lled genome-wi associatn studi intified a gene lled SLITRK6, which is active a bra regn lled the diencephalon that differs size between people who are homosexual or heterosexual. While there is no sgle “gay gene, ” there is overwhelmg evince of a blogil basis for sexual orientatn that is programmed to the bra before birth based on a mix of geics and prenatal ndns, none of which the fet choos.

SEARCH FOR 'GAY GEN' COM UP SHORT IN LARGE NEW STUDY

However, spe such tenuo provenance, the gay gene has persisted as a reference science news, popular science wrgs, and prs releas and edorials about bmedil rearch. News media monstrat that the gay gene has bee an assumed back-story to geic sexualy rearch over time, and that the crique of s very existence has been dimished. The nsequent unmoorg of the gay gene om acuntabily and accuracy monstrat that the anizatn of bmedil databas uld benef om greater cross-disciplary attentn.

NEWS: 'GAY GEN': SCIENCE IS ON THE RIGHT... (THE GUARDIAN) - BEHD THE HEADL

Still others, backg the same e, disurage any vtigatn to the blogil origs of sexual orientatn, fearful that posive rults will lead to attempts to rid the world of potential homosexuals. For them, the disvery of how an dividual be gay is likely to shed light on how sexualy-related gen build bras, how people of any persuasn are attracted to each other, and perhaps even how homosexualy evolved. Hamer had jt published a study that claimed not only to have fally proved that male homosexualy was at least partially geic but also to have ppoted the stretch of chromosome where one of the gen volved rid.

Hamer and his lleagu nducted extensive terviews wh 76 pairs of gay brothers and their fay members and found that homosexualy seemed to be hered through the maternal le.

GAY GEICSMOST OF BELIEVE THAT WE WERE BORN THAT WAY, BUT IS SEXUAL ORIENTATN OUR DNA? JV CHAMARY GO SEARCH OF THE GAY GENEJV CHAMARYPUBLISHED: MAY 31, 2009 AT 11:00 PMGAY GEICS

Yet Hamer ntends that his rults suggt there is a lk to Xq28 and that the Rice study was biased bee one of the thors told Hamer that he didn’t believe a gay gene uld exist.

Whether or not a gay gene, a set of gay gen, or some other blogil mechanism is ever found, one thg is clear: The environment a child grows up has nothg to do wh what mak most gay men gay. Ially, Bocklandt would sn the genome of each dividual, lookg for a methylatn pattern anywhere on any chromosome that shows up repeatedly the gay member of each tw pair.

Alan Sanrs, an associate profsor of psychiatry at Northwtern, will be lookg at the whole genome of about 1, 000 gay brothers g the geic marker technique that Hamer ed. By settg up a stand at Gay Pri paras and approachg “gay iendly” groups like PFLAG (Parents, Fai and Friends of Lbians and Gays), Sanrs has found more than 4, 000 gay men wh a brother who are terted participatg.

THERE’S (STILL) NO GAY GENE

Even if social prsur through the ag led some gay men to have some children, the signifintly lower rate of reproductn would eventually lead to the disappearance of the gene (as Hamer do note his book, The Science of Dire: The Search for the Gay Gene and the Blogy of Behavr).

) The creased number of grandchildren that a parent might have through such a superfertile dghter would offset whatever loss of geic postery om havg a gay son.

THE 'GAY GENE' IS A TOTAL MYTH, MASSIVE STUDY CONCLUS

Andrea Camper-Ciani, a profsor of ethology and evolutnary psychology at the Universy of Padua, terviewed 98 gay men and 100 straight men and found that the mothers of gay men had an average of 2.

”Another way to pass on the seemgly nonreproducg gay gene would be for a nonreproducg gay man to have an extra tert seeg that the offsprg of his siblgs survive. In addn to lookg at how they spent their money, Rahman tried to see if gay men had some kd of extra psychologil generosy by askg qutns like, “Assumg you had a ln pounds, would you buy gifts for your fay? But 21st-century Wtern society, and the homosexuals there, uld be somethg of an anomaly human history, acrdg to Pl Vasey, an associate profsor of psychology at the Universy of Lethbridge Alberta.

THERE’S NO ONE ‘GAY GENE,’ BUT GEICS ARE LKED TO SAME-SEX BEHAVR, NEW STUDY SAYS

Another problem wh kship selectn studi that look only England and, particular, the Uned Stat, is that kship ti for homosexuals might not be as strong as they would be elsewhere. “The Uned Stat is profoundly homophobic, ” says Vasey, “so you n’t be directg altism at your fay members if they’ve kicked you out and you’ve moved to the other si of the untry.

To put the kibosh on the ia that the evolutn of a gay gene prents an unsolvable nundm, Sergey Gavrilets, a theoretil evolutnary blogist at the Universy of Tennsee, veloped a mathematil mol of how a set of what he lls “sexually antagonistic” gen might evolve. ”) But he did clu Camper-Ciani’s rults and also assumed that gay gen would be passed down on the mother’s si, on the X chromosome, as dited by mol shows that over centuri an effect you might ll the homophobe’s paradox has been at work on the human genome: The more tolerant the society, the more likely is to mata gay gen. Image, for stance, that for every extra child that such a gay gene–rryg woman has, a gay man n have one fewer and the balance necsary for the survival of the gene is still mataed.

IS THERE A “GAY GENE"?

” On the other hand, the more tolerant the society, the more gay men n be ee to be who they are, so the more likely they will be childls—and the more difficult will be for any female the fay to make up for the loss. If the likelihood that a uple’s first son will be gay is 2 percent (a reasonable gus), Blanchard says, the probabily that the 5th son will be gay is only 6 percent.

The real evolutnary st of beg homosexual isn’t too big if you’re forced to have olr-brother effect acunts for about 15 to 30 percent of gay men, Blanchard timat. Comparg the gray matter the davers of gay and straight men, he found that an area the anterr hypothalam known as INAH-3 was smaller gay men, about the size is women.

GAY GENEALOGY AND GAY FAY HISTORY INFORMATN

Ivanka Savic Berglund, a nroscientist at the Karolska Instute Stockholm, put gay men, straight men, and women a PET snner (not all at the same time) and watched how their anterr hypothalam l up when prented wh an odor siar to one found men’s sweat and one siar to a scent found women’s ure. “At first blh you might thk, ‘Well, gosh, maybe gay men didn’t get enough ttosterone early life, ” says Marc Breedlove, a nroscience profsor at Michigan State Universy.

No experiment has yet led that rearchers do prove that ttosterone n alter human sexual orientatn—gay gene or no gay gene—the possibily of preventg homosexualy will bee a realy. And bee the rearchers didn't fd gene variants that rrelated wh a gradient of sexual behavr, she says, unrcuts Aled Ksey's s-old sle, which ranked people on a spectm of sexualy, om exclively heterosexual to exclively homosexual.

“Conservative, right-wg people hated bee they felt that was sayg that beg gay is like beg black, that was -born, that would somehow ‘exce’ gay people or give them more rights, ” says Hamer. “On the other hand, gay people hated too bee, at that time, there were fears that the disvery would be mised to abort gay babi and wipe gay people off the face of the Earth. Although the fears rema, recent years the search for ‘gay gen’ has bee more accepted by the gay muny, no small part bee a blogil explanatn wouldunrme arguments that beg gay is a social or liftyle choice.

MANY GEN INFLUENCE SAME-SEX SEXUALY, NOT A SGLE ‘GAY GENE’

For stance, intil tw brothers (siblgs rived om the same fertilised egg) are more likely to both be gay than aternal tws (tws that velop om separate eggs). Now chief of the gene stcture and regulatn sectn at the US Natnal Cancer Instute, his study revealed a cur pattern: gay men tend to have more gay uncl and gay male s on their mother’s si of the fay than on their father’s.

To track down the DNA regn lked to the gay tra, Hamer ed a technique lled ‘lkage mappg’, an approach that lets geicists fd a gene even when they don’t know what do or where ’s loted. The exceptn is homosexual men’s bras, which show remarkable siari to the bras of heterosexual women, suggtg that sexual orientatn pends on the effect hormon have on the velopg bra. Blanchard believ that homosexualy is “100 per cent blogil”, and timat that the aternal birth orr effect acunts for 15-30 per cent of gay men the populatn.

Not only did he replite Blanchard’s birth orr effect, he also tected herance of homosexualy on the mother’s si, supportg Hamer’s ia of a gay gene on chromosome X.