A genetic theory of homosexuality.
Fifth, the benefits aren't really confined to women. They protect society as a whole. The authors' computations indicate that as a society's birthrate falls, female carriers of androphilic genes account for a larger share of the output. In short, the genes provide a "buffer effect" against extinction.
The study's lead author, Andrea Camperio Ciani of the University of Padova, sees these ramifications as a happy ending. "This is an example where the results of scientific research can have important social implications," he tells LiveScience. "You have all this antagonism against homosexuality because they say it's against nature because it doesn't lead to reproduction. We found out this is not true because homosexuality is just one of the consequences of strategies for making females more fecund."
But the word consequence suggests a sixth, less happy implication: How would gay men see themselves and be regarded in a society that understood their condition as a side effect of female evolution? Would male androphilia be treated like sickle-cell anemia—the unfortunate cost of a genetic mutation that's beneficial in other people? We medicate sickle-cell anemia. Would we medicate homosexuality?
I don't know, and neither does Dr. Camperio Ciani. Science, like culture and politics, has its happy moments. But don't mistake them for endings.
Will Saletan covers science, technology, and politics for Slate and says a lot of things that get him in trouble.
Illustration by Mark Alan Stamaty. Photograph of a gay couple on Slate's home page by Medioimages/Photodisc/Getty Images.