Let your fingers do the talking

31 March 2000
Newsweek magazine

Let your fingers do the talking
By B. J. Sigesmund

For Marc Breedlove, all it took was a Xerox machine and a dream.

The University of California at Berkeley professor, who studies the biology of sexual orientation, took his copier and a few assistants to three street fairs in San Francisco last fall. His quest: to see if hormones in the womb might play a role in sexual behavior. At each event, he offered passersby a $1 lottery ticket in exchange for information regarding their sexual orientation and their birth order–and a copy of their palmprint. The psychologist collected data from 720 people.

The results, published this week in the journal Nature, stir the debate over whether homosexuality is learned, influenced or fixed by prenatal factors. Scientists have long believed that finger lengths may indicate the levels to which a fetus was exposed to male sex hormones, such as androgen, while in the womb. Now Breedlove’s research indicates that both women’s and men’s finger lengths might signal sexual orientation, suggesting that hormonal exposure is one determining factor in sexuality. “We expected any such effects to be subtle because so many factors play a role in human behaviors,” he says. “So we were excited to find [some] evidence.”

Breedlove’s team found that the women interviewed who identified themselves as lesbian tended on average to have “finger-ratios” that were more like men’s. A person’s finger-ratio is the index finger’s length divided by the ring finger’s length. In men, the average ratio is 0.95. For women, 0.97. Lesbians who participated, the Berkeley team found, scored 0.96.

The study of the finger-ratios of straight men and gay men who were interviewed proved more complicated. Breedloves researchers found no difference between the straight and gay men’s finger-ratios until they separated the men by birth order. Then they found that gay males who had two or more older brothers had slightly lower ratios than those with no older brothers. And lower ratios in males are a possible indication of homosexuality, Breedlove believes.

Breedlove says his study corresponds to the work of an associate in his field, Ray Blanchard, who’s shown that boys who have greater numbers of older brothers have a higher likelihood of being gay. Blanchard says he thinks Breedlove’s study furthers the theory that hormones in the womb have an effect on the eventual sexual orientation of the fetus. “You can’t learn your finger length, and your finger length is not a lifestyle choice,” Blanchard says.

What’s next? In order to further validate the research, another researcher must replicate Breedlove’s exact findings in a second survey of both straight and gay people. Blanchard believes it won’t be long. “You don’t need an atom smasher,” he says, “only a photocopier.” Some lottery tickets wouldn’t hurt either.

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