(It might tick off the left-handed folks too.) is some kind of biological error,” he says. “It’s essentially saying that homosexual preference. It’s a politically sticky idea, says Qazi Rahman of Queen Mary-University of London. What it might mean: One guess is that different-than-normal levels of testosterone in the womb - widely theorized to play a role in determining eventual sexual orientation - could nudge a fetus toward brain organization that favors left-handedness as well as same-sex attraction.Īnother theory is that development of a fetus might be disturbed by factors such as a mother’s illness, steering the fetus into being less than strictly right-handed - and, in some cases, less than strictly heterosexual. An analysis of more than 23,000 men and women from North America and Europe in 2000 found that being non-right-handed seems to increase a man’s chances of being gay by about 34%, and a woman’s by about 90%.
The numbers: More lefties - or at least more somewhat-ambidextrous folks - crop up in the gay population than among straight people, several studies have shown. The hand you use to sign your name might have something to do with what gender you are drawn to. Subsequent sons in the womb could be exposed to these “anti-boy” antibodies, which might affect sexual development in the brain.Īccordingly, you’d expect the percentage of gay men in a society to vary depending on demographic differences in family size: One study calculated that a one-child-per-family law would reduce male homosexuality by about 29% from current levels. After giving birth to a boy, her immune system might create antibodies to foreign, male proteins in her bloodstream. What it might mean: Psychological influences are probably not at work, because the pattern holds even for gay men who weren’t raised with their older brothers. So having one older brother ups the chance to only about 2.6%. A man’s chance of being gay is pretty low to begin with - perhaps as low as 2% (lowered from 10% by researchers in the early 1990s). The numbers: Each older brother will increase a man’s chances of being gay by 33%, says Ray Blanchard of the University of Toronto, an expert on the “big-brother effect.” That’s not as dramatic as it might sound. Study after study - including one of 87,000 British men published last year - has found that gay men have more older brothers than straight men do.
( A link between male homosexuality and finger lengths isn’t holding up, and a claim that gays have distinctive fingerprint ridge patterns is largely discredited.) Scientists don’t always agree on how to interpret the results, and more progress has been made with regard to men than to women. Studies contradict each other, and some promising paths don’t pan out. Some inborn traits might be expected if homosexuality is - as most scientists believe - rooted in biology, and they might provide clues about the biological origins of sexual orientation.įinding and solidifying these links isn’t easy. So measuring a subject’s shoe size is permissible asking about ownership of Barbra Streisand albums would be cheating. These scientists are searching for innate traits that might not appear to be related to sexual orientation or even to standard clichés.
The preferred term is “sexual orientation correlates.” But some scientists are, in a way, working on gaydar, the supposed ability to discern whether a person is homosexual by reading subtle cues from their appearance. John McCain dropped by “Saturday Night Live,” drawing laughs from his promise, if elected president, to fight expensive federal projects - such as, he spoofed, a Department of Defense device to “jam gaydar.”