Oh So Natural

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?

It just doesn’t fit any of the data we have. Darwin had very specific sex roles for males and females. He wrote that females are docile and dainty and always prefer mates who are attractive and vigorous. But the world doesn’t work like that. A quick look at humans tells you that women don’t always prefer musclebound models. It’s really obvious, but women choose all kinds of men as mates, and very rarely do those choices have to do with exhibited traits, like the peacock’s tail or a stag’s antlers, that Darwin thought represented “good genes.”

In fact, the whole good-gene idea is suspect. The idea that a female could look at a male and tell by his appearance how good his genes are and how those genes are going to play out in 20 years is extremely far-fetched. Scientists have been trying to prove this idea experimentally, and it never bears out. It doesn’t bear out, because not even supercomputers can offer that kind of predictability.

What about sexual selection and homosexuality?

Homosexuality is the other problem with sexual selection. According to Darwin, the only purpose for sex is the transfer of sperm. And if he’s right, then homosexuality is a biological dead end. But he isn’t right. Most mating takes place without chance of conception. Humans have sex all the time, but produce very few offspring during their lives. A typical couple has sex once a week for 50 years, but has only two offspring. If the only goal of sex is the transfer of sperm, then it’s a very inefficient method for doing so. One of the other things Darwin’s theory teaches us is that when a species exhibits a trait that is inefficient, it is selected against. So, unless evolution has somehow overlooked sex, making it inefficient in contrast to all the other, wonderfully adapted traits that have evolved, then mating must really be serving multiple functions of which one is the occasional transfer of sperm.