Straight Talk About Gays

Gene Expression has a post titled "More Fodder for the SPLC and James Dobson" on two articles about research into the biological underpinnings of homosexuality. The Boston Globe article "What Makes People Gay?" mentioned in the blog entry does a nice job of summarizing the various studies that have been done and in the end decides that there's definitely a biological/nature factor.

The big problem with positing that homosexuality is driven by genetic factors is how is it not eliminated by Natural Selection? The author brings up baseless suppositions that homosexuality is caused by a virus, and gleans over other explanations that cite compensatory benefits.

Leonard Shlain in his book Sex, Time and Power thinks maybe the main benefit to having a homosexual male in a hunter/gatherer family is the extra meat he brings in that he doesn't have to share with a mate or children -- in that case he'd most likely share it with a sister and her children. A similar benefit with lesbianism is that without children of her own she'd be free to help her siblings with their children. Shlain says (pg. 241):

"Although poorly understood, selective pressures in the human species have ensured gay behavior in every generation and in every culture. [Homosexuality's] ubiquity suggests that it is a very old trait and was likely present at the dawn of our species. Perhaps this unique development arose from the need to enhance the survival of a primate species that had precipitously switched its diet from roots and shoots to haunches and hamhocks in order to provision burdened mothers and their children with intelligence-enhancing brain food. The insertion of [homosexuals] into the human genome was one of four adaptations that Natural Selection cleverly slipped in among the chromosomes to assist newly minted Homo sapiens hunter in his deadly competition with other species for survival. A dollop of the same mysterious formula was also ladled into Gyna sapiens chromosomal potpourri, so that lesbians would also be mixed into each generation. . . I shall call my thesis the Theory of Eights. Four unique human traits appear in any given Homo sapiens population, and each one uncannily hovers around the stable level of 8 percent of the males. The four are [homosexuality], color-blindness, left-handedness, and baldness. Eight percent roughly equals about one out of twelve men. I believe that these four traits taken together represent a constellation of genetic adaptations that enhanced the success of the original human male hunting band."

Now, Shlain isn't an evolutionary biologist (he's the chief of laparoscopic surgery at California-Pacific Medical Center in San Francisco) and I don't know how you could test this hypothesis. However, I like this theory because it provides an explanation for homosexuality without claiming that it's some kind of malformation, problem with embryonic development or some other way abnormal. I'd also like to check his 8 percent number for the occurence of color-blindness, left-handedness and baldness.