Evolutionary psychologist Gordon Gallup has an interesting (if controversial) theory about the origin of both homosexuality and homophobia. I'm unconvinced, but what do I know? He claims that the orientation is caused (at least in part) by early imprinting. He cites a study (Van Wyk and Geist, 1984) that revealed that males are much more likely to become homosexual if their first masturbation experience is in the presence of another male.
Gallup then suggests that man-boy contact is not uncommon. He refers to another study which found that 80 percent of homosexuals admit to having sex with minors (Goode and Troiden 1980) and that homosexual pedophiles average many more victims (150) than heterosexual pedophiles (20) (Abel et al., 1987). Another study (Cameron, 1985) estimated that homosexuals are 90 to 100 times more likely to become sexually involved with their students than are heterosexuals (I know mainstream researchers hate Cameron). The rate of recidivism among convicted homosexual pedophiles is also approximately twice that of their heterosexual counterparts (American Psychiatric Association 1994).
Gallup then reports on his own study (unpublished) of adult homosexuals. One out of four gay men had their first homosexual experience (which typically occurs during early adolescence) with a stranger who on average was 15.7 years older than they were. Most of the homosexual males in the sample also reported developing a clear sense of their sexual orientation around the time that they had their first homosexual experience.
Early same-sex experiences also happen with peers, according to Gallup (but he leaves out abuse among minors).
While this theory alone is a shock, he seems to present it in order to set up the question he is more interested in: why homophobia? Why are many heteros uncomfortable with homosexuality, while homosexuals don't seem to have an aversion to straights?
More specifically, why do people fear leaving their children with gay men? He then hypothesizes that, according to evolutionary theory, parents have a keen interest in the future fertility of their children, and will protect them from anything that would undermine their motivation to reproduce.
Gallup claims that people intuit a connection between homosexual contact and a child's sexual orientation. According to his research, people are much less comfortable with scenarios like a homosexual teacher or pediatrician caring for their child than a homosexual fixing their car or performing surgery on them. They are more comfortable with a child being around a homosexual if the child is an adult rather than if he is still a minor.
I don't buy it (my bias is biological) but I have found that homosexuals are more likely to report sexual contact as children.
UPDATE: Gene Expression describes twin research that concludes that heritability for homosexuality is roughly 50 percent. Of course, that is only half the story.
Abel, G., Becker, J., Mittelman, M., Cunningham-Rathner, J., Rouleau, J., and Murphy, W. Self-reported sex crimes of nonincarcerated paraphiliacs. Journal oflnterpersonal Violence 2:3-25, 1987.
American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 4th ed. Washington, DC: APA, 1994.
Cameron, P. Homosexual molestation of children: sexual interaction of teacher and pupil. Psychological Reports 57: 1227-1236, 1985.
Gallup, G.G., Jr. Have attitudes toward homosexuals been shaped by natural selection? Ethology and Sociobiology 16: 53-70, 1995.
Goode, E., and Troiden, R.R. Correlates and accompaniments of promiscuous sex among male homosexuals. Psychiatry 43: 51-59, 1980.
Van Wyk, P.H., and Geist, C.S. Psychosocial development of heterosexual, bisexual, and homosexual behavior. Archives of Sexual Behavior 13: 505-544, 1984.