aTypical Joe: a gay New Yorker living in the rural South
Monday, March 13, 2006
The “Older Brother Effect”
The headline from Lesley Stahl’s 60 Minutes report the other day on the science of sexual orientation:
“The more older brothers a man has, the greater that man’s chance of being gay,” says [Northwestern University psychology professor Michael] Bailey.
Asked if that’s true, Bailey says, “That is absolutely true.”
If this comes as a shock to you, you’re not alone. But it turns out, it’s one of the most solid findings in this field, demonstrated in study after study.
And the numbers are significant: for every older brother a man has, his chances of being gay increase by one third. Older sisters make no difference, and there’s no corresponding effect for lesbians. A first-born son has about a 2 percent chance of being gay, and the numbers rise from there. The theory is it happens in the womb. [...]
“One of the things we’ve only found out lately is that older brothers affect a boy only if the boy is right-handed,” [Michigan State University’s Dr. Marc] Breedlove said. “If the boy is left-handed, if his brain is organized in a left-handed fashion, it doesn’t matter how many older brothers he has, his probability of being gay is just like the rest of the population.
Parenthetically I note that Dr. BREED-LOVE’s studies of breeding in rats - he gave Stahl “a crash course in rat sex” - implicitly question the role of love as well.
Timothy Noah has a fun collection of them at Slate. My entry didn’t make the cut.
