Special to The Washington Post
Monday, February 19, 2001; Page A15
Evolutionary biologists have long wondered why homosexuality exists. Since homosexuality does not directly result in the passing of genes to future generations -- evolution's driving force -- it seems odd that it persists in so many societies. A small but growing group of researchers, however, says evidence from both human and animal societies suggests that same-sex attraction does, in fact, have an important evolutionary function.
"The recognition of how widespread same-sex courtship is, and that it has an adaptive significance, is a growing trend," said Joan Roughgarden, a biologist at Stanford University. The primary function that same-sex attraction provides, scientists like Roughgarden argue, is that it promotes the formation of alliances that help the parties involved outlive, outperform and even outreproduce competitors.
"We're using some newer concepts about sexual behavior," said Frank Muscarella of Barry University in Florida, who offered support for this theory in the fall issue of the Journal of Homosexuality. Mainstream scientists remain skeptical. The new theories rely on studies suggesting that same-sex relationships are, or have been, far more common than traditionally believed, a conclusion that skeptics question.
"My feeling is that evolutionary theory mainly helps us understand why most people are heterosexual, and why homosexuality is rare -- it's not reproductively productive," said Lee Ellis, a sociologist at Minot State University in North Dakota. "Evolution isn't very good at explaining oddities," he added. "It mainly explains where most people are."
But proponents counter that most human and animal societies have been teeming with same-sex attraction -- the real fluke is Western culture's recently developed aversion to it. For another thing, they say bisexuals far outnumber homosexuals. This idea allows them to raise the possibility that an animal could use benefits gained from a homosexual liaison, such as higher status, to reproduce more or care for offspring better.
"Most individuals who engage in homosexual behavior are, in practice, bisexual," wrote R.C. Kirkpatrick, a biodiversity specialist with the Nature Conservancy, an environmental group, who authored another paper on the subject in the June issue of Current Anthropology. Both researchers advocate dropping the distinction between "gay" and "straight" individuals. Nature makes no such distinction, and neither did most humans throughout history, they say. Research should focus on a more neutral, simple concept of homosexual or homoerotic behavior, according to the researchers.
The two researchers cite an array of examples that they say show how such activity could boost one's chances of survival and reproductive success. Kirkpatrick's paper cited studies on animals and on various stages of Greek, Chinese, Japanese and U.S. culture. Among the Sambia of New Guinea, homosexual interactions among warriors may solidify ties vital for mutual defense, Kirkpatrick argues. In some Melanesian societies, 17th-century Japan and ancient Athens, men were actually expected to be attracted to other men. The ancient Greeks' propensity for homoerotic bonds usually involved an older, higher-status male and a younger "client," who gained prestige and status through the liaison, the researchers say. In each case, homosexual bonds helped bring success and status, the authors argue. For males of most species, higher status means more access to mates.
This sets up a classic evolutionary argument: Organisms displaying homosexual activity would produce more offspring, passing their traits to successive generations. The examples the two researchers cite aren't limited to humans, or to males. Among bonobos, a type of chimpanzee, young females typically emigrate to a new group, where they promptly initiate sexual contact with dominant females. "They form 'friendships' and alliances with established females that allow them to become integrated into the group, and more importantly, allow them access to food resources," Muscarella wrote. He acknowledged that the theory has yet to pass crucial tests, such as a study of whether homosexually leaning animals indeed have more offspring.
The new research draws in part from a 1999 book by biologist Bruce Bagemihl, who also wrote that homosexual activity serves underappreciated social and family roles. The book, "Biological Exuberance," offers evidence from the animal world that homosexuality is common: lesbian pairs in several gull, goose and tern species raising young without male help; male black swan pairs raising cygnets on their own, using the female as little more than a temporary device for procreation.
In a book scheduled for publication next year, "Evolution's Rainbow," Roughgarden speculates that same-sex relations may have evolved as a glue for coalition-building among animals, including humans. This hypothesis "also explains homophobia," she said. "Same-sex coalition building is usually a threat to a hierarchy. That sets up a tension, and the alpha male is going to try to break up the coalition." No one has documented such events among animals, she acknowledged, but then again, "no one has looked."
Attempts to explain homosexuality in evolutionary terms aren't new. In past decades, some scientists speculated that evolution retained a "homosexuality gene" only because it occurred with some other, beneficial gene. Advocates of the newer research criticize such views as based on outdated assumptions, such as that homosexual behavior is a fluke, with no possible benefit to those who practice it. But it may be a while, if ever, before mainstream science accepts the newer batch of proposals.
There is also dissension among those who generally back the new research. Some of them believe there is a "gay gene"; others don't. Some contend homosexual behavior had adaptive roles from its outset; others say it started out with no function, as a byproduct of sexual evolution, although it could have picked up adaptive uses.
Another who disagrees is Dean Hamer, a geneticist with the National Institutes of Health, who has been a key player in the scientific search for a "gay gene." He advocates a theory called "sexual antagonism." This proposes the existence of a gene that causes homosexuality when it occurs in one sex, but tremendous sexual productivity when it appears in the other. Evolution retains the gene because half of its carriers transmit it to their abundant offspring.
"I think what's happened is that there's a new generation of academics, some of whom are gay, and some of whom are more open to the idea of being gay," Muscarella said. "We said these [previous] arguments don't make sense. These arguments are based on stereotypes, and we're going to put forward some new ideas."
Copyright © 2001 The Washington Post. All rights reserved.
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