“Why am I gay?” The question reverberates through every homosexual at least once in his or her life. While potentially confounding as a personal question, when one applies a little science, this question becomes an intriguing evolutionary puzzle. Homosexual behavior has been observed in more than 1,500 species. If the point of life, from an evolutionary standpoint, is to pass on useful genes, why is anyone gay?
Humans have been trying to answer that question since we began applying scientific principles to human sexuality. Unfortunately the first of those humans were Victorians who considered the “nameless offense of great enormity” so dangerous to society that they regularly sent gay men to the gallows or locked them away forever. The Victorians passed their prejudices on to later generations. As late as 1971 — 16 years before homosexuality would be struck from the Diagnostic and Statistical Manual of Mental Disorders (DSM) — a study titled “Behavioral Changes Due to Overpopulation in Mice” included homosexuality in a list of “catastrophic events” alongside increased mortality among the young, lack of maternal functions, and cannibalism.
Others questioned whether homosexuality had a genetic component and even (gasp!) evolutionary benefits. In charting the variations between hetero and homo development and physiology, we’ve learned that gay men show significant variation in the size and structure of INAH3 (a part of the brain involved in regulating sexual behavior); gays tend to produce higher levels of the “social” hormone progesterone; and curiously, the likelihood that one of her sons will be gay increases by 33% with each male child a woman gives birth to.
In 2004 an Italian research team led by Andrea Camperio-Ciani postulated that homosexuality could be explained through Richard Dawkins’ theory of “sexually antagonistic selection” wherein a set of genes might increase the procreational competitiveness of one gender while diminishing the other’s chances.
A series of studies which relied heavily on self-reporting found that the female relatives of gay men tend to be more fertile; have fewer gynecological issues; are more extroverted, funnier, happier, and more relaxed; and have fewer family problems or social anxieties than females who don’t have gay relatives. “In other words, compared to the others, [they’re] perfect for a male,” Camperio-Ciani told journalists in 2008, with what was almost certainly a total lack of irony.
This year, a study was published with the Royal Society that applied sexually antagonistic selection theories to the lives of fruit flies. Essentially robots built to eat, fly, and fuck, fruit flies are utterly lacking in cultural influence. Using some old-fashioned inbreeding, Jessica L. Hoskins, Michael G. Ritchie, and Nathan W. Bailey found an undeniable link between same-sex behavior in male flies and an increase in the fecundity of females from the same line. It is an affirmative answer to the “evolutionary benefit” question, but hardly one that satisfies emotionally. Besides casting homosexuality as the by-product of more evolutionarily useful genetic phenomena, the Royal Society study doesn’t examine the potential benefits of homosexuality.
Regarding homosexuality as population control, Dawkins has stated unequivocally that nature doesn’t “do” population limits.
Another theory holds that “gay uncles” provide benefit by being more likely to look after nieces and nephews. The homosexual fa’afafine of Samoan culture are more likely to exhibit such avuncular behavior than their heterosexual siblings, yet this behavior has not been seen in Japanese or American gays.
My favorite theory envisions the gay man as bridge builder and peacemaker. Citing examples from such far-flung settings as pre-colonial Hawaii, medieval Florence, and feudal Japan, anthropologist R.C. Kirkpatrick has theorized that gay sex can help build relationships and form alliances for both individuals and families. It fits with what we know about the physiological traits of gay men and the environmental realities which increase the likelihood of homosexual behavior — large families already dense with aggressive males and overcrowded living situations with limited resources are both scenarios where more cooperative, socially inclined males could come in handy.