The Most Natural Selection

For a long time there have been two paramount arguments against homosexuality. The first came from the Bible. The King James Version of Leviticus 18:22 is quite clear: "Thou shalt not lie with mankind as with womankind: It is abomination." Then again, in that same Bible, Exodus sanctions selling one's youngest daughter into slavery. In fact, elsewhere in the Good Book, we're told that a woman caught wearing garments made from two different threads should be burned to death and that a man caught planting the wrong crops must be stoned to death. Oddly, the folks who most often use the Bible to defend their bigotry fail to mention these absurdities.

Darwin, whose theory of evolution says that all life originated from a common ancestor, made the other frequently cited argument against homosexuality. The reason the tree of life is so varied is because reproduction is an inexact process. Mutations arise that either help or hinder existence. Helpful ones create new lineages; harmful ones die off. "Survival of the fittest" is an abridged way of saying organisms with mutations that increase the species' chances of reproduction do better than ones that don't.

But mutation alone doesn't explain all the variety in nature. To address that, Darwin developed his idea of sexual selection. Sexual selection is meant to explain how things like a peacock's ornamental tail -- obviously a hindrance to survival (have you ever tried running away from a predator with a kite tied to your ass?) -- exist. Darwin figured, simply, that peahens (female peacocks) must like the tail. In fact, Darwin supposes, the male with the biggest tail attracts the most females. So, in Darwin's theory of evolution, mutations that are not in the service of survival -- as are speed, camouflage and opposable thumbs -- must be in the service of attracting mates with which to propagate the species.

Which puts homosexuality, which is clearly not a reproduction-enhancing mutation, at odds with Darwinism. Which, in turn, has made strange bedfellows out of sworn enemies: Evolutionary scientists and Christian-right literalists both agree, for different reasons, that homosexuality is unnatural.

Now, while the rest of the country is grappling with the issue of gay marriage, Stanford evolutionary ecologist Joan Roughgarden is trying to untangle Darwin's mess by publishing Evolution's Rainbow: Diversity, Gender and Sexuality in Nature and People. Roughgarden's thesis begins with the idea that since homosexuality is not a reproductive strategy, according to Darwin it's an aberration that should die off. But instead of deciding that homosexuality is wrong from an evolutionary standpoint, Roughgarden arrived at another conclusion: Darwin's theory of sexual selection must be wrong. Traveling this path and others, her book marks the first time that a scientist has presented a cogent challenge to one of Darwin's sacred cows.

L.A. Weekly: What made you start to question the traditional view of homosexuality in biology?

Joan Roughgarden: In June of 1997, I was marching in San Francisco's gay-pride parade. It was an epiphany. I was stunned by the sheer numbers of gay people. I had read, like everyone else, Kinsey's report that gays are one out of every 10 people -- a series of subsequent studies have backed up his original data, and even the most conservative of those put the number at one in 20 -- but to see that play out in the world was startling. I knew that my subject of biology taught that something's wrong or defective in the very people standing on the sidewalks and marching in the parade. And I felt that if a theory says there's something wrong with so many people, then maybe it's the theory that's wrong and not the people.

Why are you convinced that Darwin's theory of sexual selection is wrong?