Our own species has been talking, volubly and passionately, for at least 50,000 years, and it's a fair guess that arguments about right and wrong were prominent in our conversation pretty much from the beginning. We started writing things down 5,000 years ago, and some of our first texts were codes of ethics. Our innumerable volumes of scripture and law, our Departments of Justice, High Courts, Low Courts, and Courts of Common Pleas are unique in the living world. But did we human beings invent our feeling for justice, or is it part of the package of primal emotions that we inherited from our ancestors? In other words: Did morality evolve?

Dutch-born psychologist, ethologist and primatologist Frans de Waal has spent his career watching the behavior of apes and monkeys, mostly captive troupes in zoos. As a young student, he sat on a wooden stool day after day for six years, observing a colony of chimpanzees at the Arnhem Zoo. Today he watches chimpanzees from an observation post at Emory University's Yerkes National Primate Research Center in Atlanta and at other zoos and primate centers. His work, along with primatologist Jane Goodall's, has helped lift Darwin's conjectures about the evolution of morality to a new level. He has documented tens of thousands of instances of chimpanzee behavior that among ourselves we would call Machiavellian and about as many moments that we would call altruistic, even noble. In his scientific papers and popular books (including Chimpanzee Politics, Our Inner Ape and Good Natured), he argues that Darwin was correct from that first glimpse of Jenny at the zoo. Sympathy, empathy, right and wrong are feelings that we share with other animals; even the best part of human nature, the part that cares about ethics and justice, is also part of nature.