Apes That Swing Many Ways

In a forest clearing near Wamba in equatorial Zaire, a group of bonobos, or pygmy chimpanzees, approaches a juicy stash of sugarcane laid out by Japanese researchers. As the animals draw near the sweets, they begin an astonishing series of sexual interactions. Some females embrace, rubbing their genitals against each other; males rub rumps, and sometimes briefly enter into what looks like mating. There is plenty of heterosexual sex too, as well as adult- infant encounters and enough mixing and matching to offend every puritanical sensibility. Scientists have observed similar orgies when bonobos converge on fig trees ripe with the sticky...