Health & Well Being
Everybody Clap Your Hands: New Reaseach Uses Finger Length to Divine Sexuality
Everybody Clap Your Hands:
New Research Uses Finger Length to Divine Sexuality
by Heather K. Peake
A new study out of the University of California at Berkeley is going to have a lot of people scrutinizing their hands.
Dr. Marc Breedlove’s hypothesis is simple: high levels of male hormones in utero can be a causal factor in the development of homosexuality.
But it was the research method cited in his controversial paper, which appeared in last month’s issue of Nature, that lit up the eyes of media people around the world: Breedlove, a professor of psychiatry who studies the biology of sexual orientation, measured the fingers of gay men and women.
He and his student assistants conducted their research in the summer of 1999. Armed with detailed questionnaires and a portable copier, they attended several San Francisco street fairs, and eventually interviewed 720 people.
Then, wielding a ruler, Breedlove went to work. He focused his attention on two digits: the index finger, designated 2D, and the ring finger, called 4D. The length of these fingers has long been known to be controlled by male hormones known as androgens 2D:4D (no, it’s not a droid from Star Wars).
Usually, a woman’s index finger is the same length as her ring finger. In the typical male, the ring finger is considerably longer than the index finger.
Breedlove’s study found that lesbians tend to have a more “masculine” 2D:4D ratio - a longer ring finger. This is a clear indication that some women were exposed to a higher level of androgen in the womb.
In gay men, the evidence was less clear-cut. Sometimes finger length was indistinguishable from heterosexual men; other times, the difference was marked.
“This calls into question all of our cultural assumptions that gay men are feminine,” Breedlove said.
The Womb’s Memory
The Berkeley study confirmed research conducted back in the 1990s showing that a high proportion of gay men have several older brothers. Breedlove found that the smaller 2D:4D radio was seen only in cases where there were two or more older brothers.
“It was a big surprise to me that the finger measures would follow the epidemiology so closely,” he said.
“We think it is inescapable that the mother’s body is remembering how many sons she has carried before, and somehow she is then increasing the amount of androgen that each subsequent son sees before birth,” the Nature article concluded.
“So the fascinating questions are: where is the memory being stored in the mother’s body and what is she doing to change the amount of androgen that each subsequent son sees.”
While Breedlove’s conclusions are interesting, they do not constitute absolute proof of a biological basis for homosexuality - as even Breedlove concedes.
“There is no gene that forces a person to be gay or straight,” he said. “I believe there are many social and psychological, as well as biological, factors that make up sexual preference.”
“Having said that, these data do suggest that there are people in the world who are gay because of fetal androgen levels.”
No Simple Answers
Other researchers disagree. University of Liverpool scientist John Manning says he has found exactly the opposite: in his study, gay men’s finger length tended to be more “feminine,” meaning 2D and 4D were about the same length. He believes that both high and low levels of androgen may influence sexual preference.
Manning also points out that Breedlove’s study didn’t take into account ethnic variations in finger measures. “The geographical differences swamps the sex difference,” he says. “There’s more difference between a Pole and a Finn than a man and a woman.”
Solving the mystery will be hard. “I think this is a possibility,” Dr. Richard Sharpe of Edinburgh University told the BBC. “But no one has actually measured the levels of androgens in [fetuses] or the women – you can imagine it is difficult to do – so this is all speculation. It may be informed speculation, but I think when we get on a subject as touchy as sexual orientation, we need to clearly define what is speculation and what is fact.”
Breedlove himself warned that this data should not be misused. “There are plenty of gay men who are first-born, many straight men with older brothers and many women whose fingers give no clue to their sexual orientation,” he said. “This is not a test to be used on your friends and neighbors.”