The TIME 100

Humans like to anthropomorphize. We ascribe human traits to what is nonhuman to bridge the gap—our version of emotional spackle. So computers become temperamental; dogs enjoy wearing sweaters. But what can we learn if we reverse the process and look for animal characteristics in ourselves?

Dutch-born primatologist Frans de Waal, 58, has been asking and answering that question for more than 30 years. The C.H. Candler professor of primate behavior at Emory University in Atlanta, De Waal sees humans as bipedal, bipolar apes. Trained in zoology and ethology, he has spent his career as a learned contrarian. Biologists and evolutionary scientists focus on competition, on what drives us apart. De Waal focuses on what brings us together: reciprocity, empathy, conflict resolution. Primates and Philosophers, De Waal's eighth book, released last year, argues that morality is not a high trait we acquired late but is etched into our instincts.

That's not to say we always behave. There are Machiavellian leaders among chimps, for example, and De Waal believes there is a straight line to be drawn from that to human politics. (Newt Gingrich recommended De Waal's Chimpanzee Politics for freshman Representatives in 1994.) A new study by De Waal and others found the roots of human gestures that accompany speech in similar signaling by bonobos. We may accept that we are descended from apes, but it takes the likes of De Waal to remind us that we haven't traveled that far.