Editors' Note: Guest blogger Dr. Helen Fisher is the founder and Chief Scientific Advisor to Chemistry.com. Dr. Fisher will be posting every Sunday evening for the next month, so someone fix her a plate.
I am a public speaker by trade; I speak on the evolution and future of sex, romance, marriage, adultery and divorce. And one of the first questions I am always asked is: "Why homosexuality?"
For years I have given the standard anthropological answer: kin selection. In short, we share our genes with relatives. So those who help their relatives are actually nurturing some of their own DNA. Hence gays and lesbians pass on their genetic proclivity for homosexuality by helping nieces, nephews and other kin.
It's a fine theory. With caveats. Foremost, a considerable number of gays and lesbians have children of their own, passing on their DNA directly.
Moreover, there is no evidence in industrial societies that childless gays and lesbians actually do put extra effort into helping kin.