Evolution's Rainbow

An interesting counter-argument to Darwin's theory of sexual selection.

Some light Saturday reading from Seed Magazine...

Male big horn sheep live in what are often called “homosexual societies.” They bond through genital licking and anal intercourse, which often ends in ejaculation. If a male sheep chooses to not have gay sex, it becomes a social outcast. Giraffes have all-male orgies. So do bottlenose dolphins, killer whales, gray whales, and West Indian manatees. Japanese macaques, on the other hand, are ardent lesbians; the females enthusiastically mount each other. Bonobos, one of our closest primate relatives, are similar, except that their lesbian sexual encounters occur every two hours.

As this list of activities suggests, having homosexual sex is the biological equivalent of apple pie: Everybody likes it. Nevertheless, most biologists continue to regard homosexuality as a sexual outlier. According to evolutionary theory, being gay is little more than a maladaptive behavior.

Joan Roughgarden, a professor of biology at Stanford University, wants to change that perception. After cataloging the wealth of homosexual behavior in the animal kingdom (over 450 different species) in her controversial book Evolution’s Rainbow, Roughgarden has set about replacing Darwinian sexual selection with a new explanation of sex. For too long, she says, biology has neglected evidence that mating isn’t only about multiplying. Sometimes, as in the case of all those gay sheep, dolphins and primates, animals have sex just for fun or to cement their social bonds.

According to Roughgarden, gayness is a necessary side effect of getting along. Roughgarden argues that homosexuality is a defining feature of advanced animal communities, which require communal bonds in order to function. “The more complex and sophisticated a social system is,” she writes, “the more likely it is to have homosexuality intermixed with heterosexuality.”