Among primates, perhaps the most pervasive, and most enthusiastic expression of homosexuality is found amongst bonobos (a species fairly closely related to common chimpanzees). Bonobos live in highly cohesive communities. Social bonds are maintained by a very high level of sexual interaction that include all possible pairings and many different positions. Males and females are bonded together and copulate frequently, sometimes face-to-face. But females frequently rub their genitals together. Males also engage in frequent sexual interactions. Bonobos are perhaps the most bisexual species of vertebrate on the planet. The bonobos do it all. For instance, males engage in highly unusual "xxxxx fencing" that involves rubbing their erect xxxxxx together.
Frequent sexual interaction among bonobos defuse aggression and strengthen social bonds. Perhaps for that reason, bonobos are less aggressive towards each other than common chimpanzees are. Bonobo antics provide a fairly compelling argument against anyone who holds that homosexual behavior is "against nature."
Of course, bonobos are not exclusively homosexual, like some penguins, or humans. In the last post, I argued that exclusive homosexuality in humans can be partly explained in terms of genes on the X-chromosome that increase reproductive success for females who carry them. The penguins remain something of a puzzle.
Bisexuality is much more easily explained because bisexuals can form close bonds with either gender, that could provide practical advantages, as hypothesized for bonobos. Anthropologists describe bisexual conduct as common in many societies around the world and conclude that close same-sex relationships provide advantages in education, trade, and the making of political alliances (2).