Lots And Lots Of Gin

Jesse Bering, a gay experimental psychologist, lists a few of the odder evolutionary theories for homosexuality. This is my favorite:    

John Maynard Smith is often credited with what is colloquially called the "sneaky f*cker theory," which argues that gay men in the ancestral past had unique access to the reproductive niche because females let their guards down around them and other males didn't view them as sexual competitors. (I rather like this one: remember, we're not infertile, we're just gay. Although in my case, it'd take a lot of gin to work.)