Are Younger Brothers More Likely to Be Gay? | Psychology Today

Contents:

• GAY GEICS
• MOM'S GEICS COULD PRODUCE GAY SONS
• ARE YOUNGER BROTHERS MORE LIKELY TO BE GAY?
• MEN WH OLR BROTHERS ARE MORE LIKELY TO BE GAY, STUDY SUGGTS
• NAVIGATG ONE SON'S G OUT N BE A BIG AL. FOR PARENTS WH SEVERAL GAY CHILDREN, N BE OVERWHELMG

GAY GEICS

It’s held aloft by Dr Alan Sanrs and a group of lleagu om NorthShore Universy near Chigo who are attendg a gay pri ftival. “The people participatg our study are terted ntributg to this kd of scientific knowledge and want to unrstand at least part of how they me to be the way they are, ” Sanrs search for ‘gay gen’ go back to 1993, when a US team led by Dr Dean Hamer scribed a regn of DNA loted on the X chromosome lled Xq28.

MOM'S GEICS COULD PRODUCE GAY SONS

“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. ”More like thisAlthough 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 would unrme arguments that beg gay is a social or liftyle choice.

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). The fact that intil tws have the same DNA and aternal tws share 50 per cent suggts that male homosexualy is gay geneIt was sctisg fay tre to see how homosexualy is hered that led Hamer to the disvery of Xq28. 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.

This is bee mal her their X chromosome om their 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.

ARE YOUNGER BROTHERS MORE LIKELY TO BE GAY?

Lkage mappg works bee close relativ like brothers share not only a particular tra, such as homosexualy, but also the gen unrlyg the tra.

So, if you study many pairs of gay brothers and fd a DNA regn that’s the same more than 50 per cent of s, ’s likely to be lked to homosexualy.

A subsequent study 1999 failed to replite Hamer’s rults and other rearchers are sceptil that Xq28 is lked to homosexualy at brothers, immune mothersMany scientists believe that exposure to hormon durg pregnancy heavily fluenc sexualy. Durg pre-natal velopment, for example, the sex ans a foet n regnise ttosterone, which will swch on gen to make om a few superficial differenc (among them penis and rg-fger length – both longer homosexuals), gay and straight men’s bodi appear the same.

MEN WH OLR BROTHERS ARE MORE LIKELY TO BE GAY, STUDY SUGGTS

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 the two factors only go so far explag how homosexualy velops.

”In 1996 Blanchard and Profsor Tony Bogaert revealed a peculiar phenomenon: the more olr brothers a boy has, the greater their chanc of beg homosexual. ”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. Fertile femalProfsor Andrea Camper Ciani at the Universy of Padova Italy has tted var hypoth by studyg 100 fai of gay men.

NAVIGATG ONE SON'S G OUT N BE A BIG AL. FOR PARENTS WH SEVERAL GAY CHILDREN, N BE OVERWHELMG

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. How would gen that e homosexualy pass om one generatn to the next, given that gay people reproduce ls than heterosexuals? Natural selectn oppos anythg that might e even a small rctn the number of offsprg you produce, so a gay tra would soon disappear om the gene pool.

After Camper Ciani scribed the observed patterns pedigre of homosexualy – the effects of maternal herance and birth orr – his dghter suggted that he re-check his data to see if the female relativ of gay men had more children on the mother’s si.