You might recognize prominent primatologist Frans de Waal from lectures he has given about his research on primate behavior, which have been popularized on YouTube.
His face is familiar to chimpanzees, too; some chimps that he knew as babies still recognize him even after decades apart, he said.
"Chimpanzees have the advantage that you cannot ask them questions, so you have to watch (their) behavior to see what they do," says de Waal, director of Emory University's Living Links Center, in his Dutch-accented voice that is both gentle and authoritative.
He adds, with dry humor: "With humans, you can ask questions and you get all sorts of answers I don't trust, so I prefer to work with chimpanzees for that reason."
Living Links is part of the oldest and largest primate center in the United States: The Yerkes National Primate Research Center, a secluded grassy area in suburban Atlanta where humans work in office trailers and other animals play in open-air compounds.
De Waal, who has been at the center for more than 20 years, has made a career out of finding links between primate and human behavior, particularly in the areas of morality and empathy.
You might think of "morality" as special for humans, but there are elements of it that are found in the animal kingdom, says de Waal -- namely, fairness and reciprocity. His latest study, published this week in the journal Proceedings of the National Academy of Sciences, suggests that chimpanzees may show some of the same sensibility about fairness that humans do.
The popular belief that the natural world is based on competition is a simplification, de Waal says. The strength of one's immune system, and the ability to find food, are also crucial. And many animals survive by cooperating.
"The struggle for life is not necessarily literally a struggle," he said. "Humans are a highly cooperative species, and we can see in our close relatives where that comes from."
Mammals such as wolves, orcas and elephants need their groups to survive, and empathy and cooperation are survival mechanisms. De Waal discusses these mechanisms in his 2009 book "The Age of Empathy: Nature's Lessons for a Kinder Society."