Homosexuality – A genetic basis?

Homosexuality – A genetic basis?

02:17 PM ET 03/29/00

Study Links Finger Size, Sexuality

Associated Press Writer

A provocative study of finger lengths found that lesbians are more likely than other women to have a subtle masculine trait, while gay men may display that same characteristic more than heterosexuals.

The research adds to an expanding body of evidence that sexual orientation is at least partly a matter of biology–and not simply a choice or a result of cultural or psychological influences.

It also provides evidence for the theory that exposure to higher levels of male sex hormones in the womb can help make a person lesbian or gay, despite the stereotype of effeminate gay men, the researchers say.

The researchers at the University of California at Berkeley built their study on an already known quirk of human anatomy: Men tend to have shorter index fingers than ring fingers. In women, those two fingers tend to be about the same length.

Scientists believe that men’s higher levels of androgens–the male sex hormones such as testosterone that are found in both sexes–produce this and many other sex differences.

In the study published Thursday in the journal Nature, the Berkeley researchers interviewed 720 adults at three street festivals in San Francisco, asked them their sexual orientation and measured their fingers.

The fingers of lesbians were closer to the typical male configuration–with the shorter index finger than the fingers of other women. The finding points to higher levels of male sex hormones in early life for lesbians, the researchers said.

The researchers also found indirect evidence of a similar trait in gay men.

They found that, in keeping with earlier research, men with more older brothers were more often gay, possibly from escalating levels of androgens in the womb for successive boys. The researchers then went a step further, showing that those same men with older brothers also had relatively shorter index fingers–the hormonal male pattern–than other men.

The researchers suspect that if they had looked at larger numbers of people, they would have found that gays overall indeed show a more masculine finger pattern than other men.

Some earlier researchers have also tied male homosexuality to unusually strong masculine traits.

“This calls into question all of our cultural assumptions that gay men are feminine,” said psychologist Marc Breedlove, who led the Berkeley study.

He cautioned that finger-length differences hold up only as averages in large populations, not for individuals. The differences involved just fractions of an inch.

Paula Ettelbrick, an activist at the National Gay and Lesbian Task Force, said some gay men would welcome such findings because “they argue very strenuously that their sexual orientation is very well defined and biological.” But she said ultimately the question of cause should not bear on the equal rights debate.

Some earlier research already suggests slight anatomical differences between gays and other men, including variations in brain structure and bigger penises for homosexuals.

The Berkeley study “is among the better lines of direct evidence of a possible hormonal cause of homosexuality,” said psychologist Ray Blanchard, a sexuality researcher at the Center for Addiction and Mental Health in Toronto.

Many researchers, including those in the Berkeley study, suspect that homosexuality stems from a complex interplay of biological, social and psychological factors.

“I think only a fool would say that we know for sure it’s biological. And I think that clearly only a fool would say it has to do only with the way we were raised,” said Bernard J. Gallagher III, a psychiatric sociologist at Villanova University.

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