Dr. Frans de Waals lets us watch a chimp fight at the Yerkes National Primate Research Center in Atlanta—in the name of science. And we turn our navel-gazing toward the furrier navels of the chimps to learn a little more about this thing called morality: where it comes from, its evolutionary benefit, and why you can't guilt-trip an ape.

Read more:

Joshua Greene: Moral Tribes: Emotion, Reason, and the Gap Between Us and Them

Frans de Waal: The Bonobo and the Atheist: In Search of Humanism Among the Primates