Animals flout established rules when it comes to the game of love and sex. In fact, the animal kingdom is full of swingers. Bonobos are highly promiscuous, engaging in sexual interactions more frequently than any other primate, and in just about every combination from heterosexual to homosexual unions. Mothers even mate with their mature sons (Everyone: Eeeeewww!). Bonobo societies "make love, not war," and their frequent sex is thought to strengthen social bonds and resolve conflict. This idea could explain why bonobo societies are relatively peaceful and their relatives, chimpanzees, which practice sex strictly for reproduction, are prone to violence.