The New York Times

October 9, 2005

'Our Inner Ape': Hey Hey, We're the Monkeys


Our closest genetic cousins, the apes, are capable of great empathy but also of violent, ruthless killing. Frans de Waal, a prominent primatologist, compares our social behavior with that of two species of apes: chimpanzees and bonobos (which look like smaller, more upright chimps). Despite their physical similarities, the two species behave very differently. Bonobos live in a relatively peaceful matriarchy; when conflicts do arise, instead of fighting they often use sexual activity to resolve them, defusing the aggression with friendly physical contact. Like hippies, they make love, not war. Chimp society, however, is a male-dominated hierarchy based on power. Unlike the gentle bonobos, who seldom kill, chimps will hunt for meat and even kill members of rival groups.

In this fascinating book, de Waal suggests that the two species represent sides of our own nature. We have "not one but two inner apes," he writes, speculating that humans may act like a hybrid of bonobos and chimps. (Little is known about actual bonobo-chimp hybrids except for a group that lives in a French traveling circus and strikes visitors with its "gentility and sensitivity.")

Helping the weak and sharing are part of both bonobo and chimp societies. De Waal gives a rather fierce example for the chimps: When individuals cooperate to hunt a monkey, they always share the meat.

Among bonobos, Kidogo, a male with a heart condition, was having difficulty adjusting to shifting routines when he was transferred to a new zoo. The other bonobos "approached Kidogo, took him by the hand and led him to where the keepers wanted him, thus showing they understood both the keepers' intentions and Kidogo's problem." Kuni, meanwhile, a bonobo at a zoo in Britain, helped an injured starling that had crashed into the glass of her enclosure. She picked it up and tried to set it on its feet, then climbed a tree and carefully spread its wings to help it to fly before she released it. "She tailored her assistance to the specific situation of an animal totally different from herself," de Waal writes.

Where the two ape species diverge most are in the realms of sex and violence. Bonobos don't exactly distinguish between sex and friendly touching. Since their behavior is so often X-rated, you will have to read the book to learn the details. There you'll also find details of chimpanzee violence. Infanticide, de Waal tells us, is a leading cause of death among chimps, both in zoos and in the wild. One reason bonobos engage in so much sex is to prevent rival males from killing their babies. If everybody has sex with everybody else, there's no saying who's the daddy.

Like humans, chimps can be ruthless toward individuals who are not part of their troop. De Waal explains that large-brained animals capable of using empathy to do kind things for others are also capable of great cruelty, because they can imagine what their victims will feel. One of the most shocking incidents he describes occurred at Gombe National Park in Tanzania, where a group of chimps lived peacefully for years. As youngsters they played and groomed one another, but the group gradually drifted apart and formed two new groups. Chimps that had known one another for years were now in conflict. "Shocked researchers watched as former friends now drank each other's blood. Not even the oldest community members were left alone. An extremely frail-looking male, Goliath, was pummeled for 20 minutes and dragged about." De Waal compares this horrible chimp behavior to genocide in Rwanda and Bosnia. With chimps, as with humans, fighting within one's own group is restrained compared with attacks on outsiders.

De Waal does not discuss the possible genetic implications of many of his observations. Animals who have high-fear genetics are less inclined to be aggressive because they are afraid to fight, and stressful, scary situations can affect them more dramatically. When bombs fell on Munich during World War II, de Waal tells us, all the bonobos in the zoo died of heart failure, but all the chimps survived. Unfortunately, he does not discuss how these differences in fearfulness might affect social behavior. Fear and other traits, like aggression and sociability, have a strong genetic component. In my own work with antelopes, I have observed huge differences in the startle and fear response between individual animals. It is likely that there may be genetic differences between the most peaceful and most violent chimps.

Also, since I am a person with autism, I do not agree with de Waal's view that emotions are required for making choices and storing memories. I use my visual thinking all the time to make logical choices. When Kuni helped the injured bird, emotion may have been the motivation, but visual thinking was the method. She compared the wing to her visual memories of flying birds and spread it to fit that image. I think her brain and mine would perform the task the same way.

De Waal's most hopeful message is that peaceful behavior can be learned, as he showed when he raised juvenile rhesus and stumptail monkeys together. The aggressive rhesus juveniles picked up peaceful ways of resolving conflict from the larger, gentler stumptails. And the lessons took: even after the two species were separated, the rhesus continued to have three times more grooming and other friendly behavior after fights. This important and illuminating book should help our own species take that lesson in civility to heart.

Temple Grandin is an associate professor of animal science at Colorado State University and the author of "Animals in Translation."