The screaming is coming from the monkey cage. The zoo visitors who have been gazing at neighboring animals--the sleepy North American black bears, the hairy and ponderous North American bisons, the leggy and brilliant flamingos--rush now to the monkey cage, like children drawn to a school-yard fight. Cashew has just bitten Cindy. Now he is chasing her up the stone steps. He corners her and glares, openmouthed. Cindy, shivering, bares her teeth and screams back. "They're so mean to each other," a woman tells her small daughter. Cashew heads to the water basin for a drink. The fracas apparently over, the human onlookers depart.
So when Cashew and Cindy sit next to each other chewing monkey chow on the feeding floor of the pen a few minutes later, those who ran to watch the fight are not around to notice. Probably they wouldn't have realized anyway that in this group of 50 monkeys, the two monkeys sitting side by side are the antagonists of a moment earlier. To untrained observers, rhesus monkeys of the same size look as similar as sparrows--most visitors to the Vilas Park Zoo here in Madison, Wisconsin, couldn't tell Cashew from Cupcake. But in fact the recent foes are snacking together now, their shoulders occasionally brushing.
Monkeys are mean: they chase and scream at each other frequently, and occasionally bite their pen mates. Scientists have noticed this combativeness for years--not just in rhesus monkeys, but in primates more similar to us genetically, such as chimpanzees. And they have said ominously that this proves aggression is part of our evolutionary heritage.
But scientists, like zoo visitors, have tended to ignore what happens after primates fight. One scientist who has studied the aftermath is Frans de Waal, of Madison's Wisconsin Regional Primate Research Center.
In a zoo in his native Netherlands in the 1970s, de Waal noted that, soon after a conflict, chimpanzees often hug and kiss. The bonobos he observed for several months in the San Diego Zoo in 1983 would fondle each other and sometimes mate after a fight. For the last decade, here at the Vilas Park Zoo, he has studied stump-tailed monkeys as well as the rhesus. After two stump-tails clash, one frequently will present its rear end to the other, who then pulls the first down into its lap. Rhesus monkeys usually just sit next to each other after a conflict, or bump lightly together, as if inadvertently. But whether the reconciliation is just brushing shoulders or mating, it serves the same purpose, de Waal says: making it clear to the combatants that the fight is over, and thus restoring the peace.
"Aggressive behavior is part of our natural heritage--but that's not the only thing we inherited," de Waal says. "There's a complement to that that keeps things in balance most of the time."
A tall, curly-haired 42-year-old with a long, well-lined face, a reedy voice, and an enduring Dutch accent, de Waal is internationally renowned for his findings on primate reconciliation. His 1989 book, Peacemaking Among Primates, has been published in nine languages. In his first book, Chimpanzee Politics, published in 1982, he documented the political maneuvering and sexual behavior of a colony of chimps in a Netherlands zoo. He frequently addresses conferences on world peace, family therapy, and domestic violence. After ten years in Madison, he will leave next month for a position with the Yerkes Regional Primate Research Center in Atlanta, where he will once again study chimpanzees.
"Forgiveness is not, as some people seem to believe, a mysterious and sublime idea that we owe to a few millennia of Judeo-Christianity," de Waal writes in Peacemaking Among Primates. "It did not originate in the minds of people and cannot therefore be appropriated by an ideology or a religion. The fact that monkeys, apes, and humans all engage in reconciliation behavior means that it is probably over thirty million years old. . . . This knowledge does not solve the problem of violence in our societies, but I do hope that it will bring a change in perspective."
In 1986, natural and social scientists from around the world met in Seville, Spain, and drafted the "Seville Statement on Violence." The statement criticized "biological pessimism" on the subject of human aggressiveness, and concluded that "biology does not condemn humanity to war."
Some of the scientists expanded on their views in a subsequent book, Aggression and War. "In many [human] societies, aggression is rare or absent," a psychologist wrote in an introductory section. "This means that, whatever the bases of human aggression, it is within the capacity of humans to do away with it."
De Waal endorses the Seville statement, but not all the assertions made by the group.
Last October, he participated in a conference, "What We Know About World Peace," in Charleston, South Carolina. Most of those attending were anthropologists. "Some of them had been working with societies that had been classified as totally peaceful," de Waal says. "In one of these societies, aggression was almost never shown in daily life--everyone seemed peaceful. On closer study, this society had a higher homicide rate than Detroit's--but the homicides were conducted through sorcery: if the people wanted to get rid of someone, a sorcerer would point at the person and say he was evil, and the person would then somehow be killed.
"So it's how you interpret these things. We had all these discussions, and came to the conclusion that if you look at these societies one by one, there's really no society without aggression. There are high and low levels, and societies where aggression is less public, but a totally peaceful people has never been found. It's unimaginable to me: I can't imagine walking into a village of people where there is never an angry word spoken, never a disagreement that leads to some shouting."
As for the idea that we should try to eliminate aggression, de Waal says with a big laugh, "Good luck. There will always be aggression--I consider that a given. There can't be a friction-free society just as there can't be a friction-free engine. Given that, we should focus not on eliminating aggression, but on how we cope with it."
De Waal grew up in a family of six boys. "With five brothers, aggression was a regular thing," he says. "Every day there would be major fights, the kind of things boys do--punching each other in the face for nothing. Maybe that's why aggression seems just a normal thing to me." The fourth oldest, he calls himself "one of the less aggressive ones. If things became tense, I tried to make jokes. I liked that solution more than making a big fuss about things." He had a "short memory" for occasions when a brother wronged him: "Five minutes later, I wouldn't care what had happened." When he fought with a younger brother, he would rush to make up with him if he heard his parents approaching, knowing well who they would side with.
At an early age, de Waal liked to fish with a net for salamanders and sticklebacks in streams near his home in the Netherlands. He'd take his catches home and try to keep them alive in an aquarium. "I killed a lot of animals when I was a kid," he says. "That's usually how you learn to keep them alive."
As a graduate student in biology in the early 1970s, he began researching what many were studying at the time: aggression. Funding for the study of aggression had been readily available since the publication of Konrad Lorenz's controversial On Aggression in 1963. Lorenz, a Nobel Prize-winning ethologist (one who studies animal behavior), had asserted that humans were predisposed to violence by evolution.
De Waal monitored a species of notoriously contentious long-tailed monkeys. "I was struck by how aggression accounted for only about 5 percent of their activity," he says. "The rest of the time they'd play, and groom, or just sit there and seem very happy with each other. I wondered how they could have these outbreaks of aggression and still have a very nice group life."
One day de Waal noted a deep gash in an armpit of the alpha--highest status--monkey of the group he was watching. The alpha monkey trembled every time his son, the second-ranking monkey, walked by: it seemed clear the son had bitten his father during a fight. Both monkeys at first showed a great deal of anxiety: the alpha monkey worried about being deposed, de Waal presumed, and his son feared a counterattack. But instead of attacking each other, the father and son began picking on other members of the group, especially one monkey whom they would corner and take turns assaulting. After a few days, the tension between the two top-ranking monkeys had abated. De Waal wrote his first article, on how scapegoating can help restore harmony. Already he was focusing not so much on aggression as on the social maneuvers that maintain a group's equilibrium. Like monkeys, people frequently look for a common enemy to keep or restore peace between them, de Waal says today.
He began observing chimpanzees in the Netherlands' Arnhem Zoo in 1975. Shortly after a major fight one winter afternoon, he watched the principals hug and kiss. The whole group of chimps celebrated the reunion by hooting loudly, and one chimp banged on drums in a corner of the pen. As he rode home from the zoo on his bike that afternoon, the word "reconciliation" came into de Waal's head. He wondered why ethologists, himself included, had overlooked such an obvious phenomenon for so long.
De Waal studied the chimps at Arnhem from 1975 to 1981. In the warm-weather months, they were kept on an island of two and a half acres. From the other side of the moat, de Waal and his students watched for squabbles. A typical skirmish between captive chimps involves "lots of barking and little biting," de Waal says. After any aggressive act--whether a threatening chase or direct physical contact--de Waal and his students watched what the aggressor and its target did for the following half hour. About 40 percent of the time, the opponents would contact each other peacefully--a high percentage, de Waal felt, considering how easy it was for the opponents to avoid each other on the large island. The contacts were different from normal ones, too: the recent foes typically extended an open hand toward each other, looked in each other's eyes, and kissed. Chimps who had been bystanders of the fight frequently offered the adversaries consoling hugs; but kissing was left to the adversaries themselves. The reconciliations were initiated equally often by dominant and subordinate chimps, and by aggressors and their targets.
But male chimps showed a far greater ability to reconcile than did females. Males fought much more often than females; but when males fought, they made up afterward 47 percent of the time, while females made up after only 18 percent of their fights.
De Waal thinks the sex difference derives from how chimps live in the wild. Males travel together in bands and depend on each other to defend their territory from bands of male chimps in neighboring territories. Their reliance on each other makes the ability to reconcile more important, de Waal says, than for females, who live dispersed over the forest with their young. Living in groups, the males are also much more status-conscious. They seem to realize that today's enemy could be helpful in tomorrow's power struggle within the group. Among the male chimps at Arnhem there was not a clear distinction between friends and foes, he says; but each female had one or two absolute enemies with whom she would never consider reconciling.
Male chimps "are more opportunistic," de Waal says, "whereas females are very good at keeping grudges. I'm tempted to say the same applies to humans. Feminists have emphasized how deep and intimate the friendships are among women. But I think the competition among women is also very intense--we just don't notice it as much, because female rivals stay away from each other. I read a study recently on how boys and girls play games. It found that boys quarrel endlessly over the rules, but they continue playing. But when girls fight over the rules, they stop the game and leave. I'm not saying the male style is better; males sacrifice a lot. Because of their opportunism, they can never trust someone completely."
In 1981, de Waal came to the Primate Research Center in Madison to study the stump-tailed and rhesus monkeys. The center is one of seven federally supported primate centers in the United States, and the only one in the midwest. Research is conducted in several buildings on the campus of the University of Wisconsin, as well as at the Vilas Park Zoo a half-mile away.
Most zoos don't display stump-tailed monkeys because of their looks, de Waal says. Their faces are patchy and freckled, with fur of various colors. They apparently don't look bad to each other, though: stump-tails, which originate in Southeast Asia, are extremely active sexually, during all seasons and every period of the female cycle. Males often copulate ten times a day. De Waal says a stump-tail named Sam, in the Netherlands, was observed mating 59 times in six hours, ejaculating each time.
Stump-tails regularly glare and scream at each other, but it's rare for one to actually hurt another: they're like an animated human family at the dinner table, de Waal says. They make up so often and so quickly that their squabbles just don't escalate. A member of de Waal's research team found the stump-tails reconciling 56 percent of the time, usually within one or two minutes of a scrap. One monkey typically would hold the other's bottom in what looks like, but isn't exactly, a mount. Kissing, grooming, and fingering or mouthing the other's genitals also characterized many reconciliations. Usually it was the subordinate monkey that presented its bottom. Females made up after fights as often as did males.
Rhesus monkeys, the most common laboratory primate, are not content to glare and scream: they often slap, grab, and bite their neighbors. They also reconcile much less often, and much less overtly, than chimpanzees or stump-tails. Since rhesus monkeys usually take direct eye contact as a threat, they don't look at each other when they're making up; this makes their reconciliations appear inadvertent. But often adversaries do seek friendly contact after a fight. In de Waal's studies at Vilas, rhesus monkeys bumped into each other or sat next to each other within ten minutes of a fight 21 percent of the time--twice as often as they did when they hadn't fought.
Like rhesus monkeys, humans often reconcile implicitly, de Waal says: friends who feud may not air their grievances, but somehow let each other know all is forgiven. "Family therapists usually have this preference for being very explicit about everything, and I'm not sure that's always the best thing. If you try to talk a conflict out, you may just get right back in the middle of it. Sometimes perhaps it's better to act as if nothing happened--but by doing something with the person you fought with, make it clear that the conflict is over."
One could hardly make up more explicitly than bonobos do. Members of the ape family, bonobos are, along with chimps, our closest genetic kin. They live in scarce numbers in central Africa, and there are fewer than 100 bonobos in zoos or laboratories worldwide--therefore much less is known about them than chimpanzees, thousands of which are in captivity. Bonobos look like sleekly designed chimps: they have a smaller head, topped by black hair parted neatly up the middle, narrower shoulders, and longer legs.
De Waal spent the winter of 1983-84 at the San Diego Zoo, observing its ten bonobos. Like stump-tailed monkeys, bonobos are very active sexually. But de Waal found that they don't seem to have sex just for fun; most of the matings are apparently designed to cool tensions. "Make love, not war, could be the bonobo slogan," de Waal says. This is particularly clear at feeding time. Aggression is at its highest then, as the bonobos compete for food; but sexual activity is also rampant. (De Waal often wondered what zoo visitors thought when they overheard him dictating into a tape recorder how many erect penises he had counted.)
Among the bonobos de Waal saw none of the prolonged hitting, trampling, and biting that chimps sometimes engage in. Compassion seemed the rule: the offending party usually initiated reunions, as if apologizing for losing its temper. When a human couple fight, then make up by going to bed, de Waal says, they are acting like bonobos.
Aggression is inevitable wherever people or other animals live together, de Waal says, because "there's never going to be a complete, 100 percent confluence of interests between two parties." And wherever there are long-standing relationships of value to the parties, there will be reconciliation, he says, to help the relationships endure in spite of the conflicts. "It bothers me that aggression is always viewed as negative," he says. "When it gets out of hand, such as in murder or rape, it of course doesn't look like a beneficial trait. But that's not what usually happens. Usually it's like a couple who can't agree on where to go for vacation: they argue, and there may be tears, but then they come to some kind of negotiated agreement."
Fighting and then making up may actually deepen relationships, de Waal believes. "Is not willingness to overcome hostile feelings the ultimate proof of commitment?" he writes in Peacemaking Among Primates. "Screaming and shouting followed by tenderness may actually strengthen a bond, in that the sequence assures both parties of the viability of the relationship. We do not trust a ship before it has weathered a storm."
When de Waal is in a restaurant, "I'm pretty much aware of what's happening at all the tables," he says. "I'm not so much following the conversations, but I notice all the nonverbal behavior. My strength in observation has always been in keeping track of a lot of things happening at the same time. That skill develops when you're studying a group of 50 monkeys." Sight has always been his primary sense, he says. He likes to draw and paint, and is an accomplished photographer: he took almost all of the photos for both of his books.
What makes watching apes and monkeys fascinating is "it's sort of a soap opera," de Waal says. "Primatologists always have these special interests--say, do males reconcile more than females?--but there's also this curiosity about how certain individuals will do, and how relationships develop over time. I remember when Orange, the alpha female in one of the rhesus groups here [at the Vilas Zoo], started associating more and more with Hulk, the second-ranking male. We were surprised that Spickles, the alpha male, allowed her to do that. We thought Hulk was making a real move to grab power in the group. Then one morning we found Orange with a big gash in her leg, being very submissive to Spickles and not looking at Hulk anymore. And we knew Spickles had put an end to all of this by attacking Orange, and that she had accepted that. Primatologists may not admit it, but it's watching these kinds of interpersonal relationships and how they play themselves out that keeps most of us going."
The monkey house at Vilas Zoo looks like a flying saucer. The round building has four sections: three of them house a troop of 50 rhesus monkeys each, and the fourth has the 35 stump-tails. The outdoor pens consist of a tiled feeding floor and an angled wall of stone steps; in the middle of the space is a large wheel for the monkeys to play on. A swinging metal door provides the monkeys access to a heated indoor pen. At the top of each stone wall are plexiglass windows, through which de Waal and his assistants and students can observe the monkeys from inside the building.
De Waal is 1 of only 2 scientists--out of 80 affiliated with the research center--currently studying the monkeys at Vilas Park Zoo. Most of the other scientists are conducting biomedical research on the 1,000 monkeys housed in the center's on-campus buildings. Researchers there are studying in vitro fertilization, AIDS, brain physiology, hair growth, dietary changes that may slow aging, the hormonal changes that occur at the onset of puberty. De Waal says that the behavioral research he does "is not the first priority of the center--I would say it's tolerated." The center is funded by the National Institutes of Health, which have never hidden their skepticism about behavioral research. Says de Waal: "There's still this stigma that everything physical or related to anatomy is more scientific than anything related to behavior or psychology." The monkeys at Vilas are not only a zoo exhibit but a breeding colony: most monkeys are taken from their troops when they're between one and two years old and brought to the on-campus buildings for biomedical studies.
In 1987, de Waal began a five-year study of how rhesus-monkey mothers influence their offspring's social environment. Rhesus mothers interfere constantly in the play of their offspring, frequently preventing them from associating with lower-ranked monkeys. The mothers sometimes "double-hold" their infant with another infant; 90 percent of the time, de Waal has found, the other infant is from a higher-ranking family--as if the mothers were trying to facilitate friendships beneficial to their children.
Many human parents likewise prevent their children from playing with kids of a lower social class. De Waal thinks his findings may teach us something about how this practice affects stratification in human society. To the National Enquirer, all this is poppycock. "Taxpayers are being skinned alive by banana-brained bureaucrats," the tabloid reported in 1987, "who are shelling out $180,000 to find out how mother monkeys raise their daughters!" De Waal's study "just proves that bureaucrats don't miss any chances to monkey around with taxpayers' money," a Republican congressman was quoted as saying.
As de Waal's prominence has grown, he has been observing monkeys less and writing and designing studies and speaking at conferences more. University of Wisconsin graduate students and primate-center staff now do most of the observing for his studies.
Chief among these has been Lesleigh Luttrell, de Waal's research assistant for the last nine years. Besides maintaining computer records and transcribing the observations that have been dictated into tape recorders, Luttrell watches the rhesus monkeys about three hours every day.
"Everyone thinks rhesus monkeys are nasty, but I don't," Luttrell says. "Short-fused, for sure. Maybe they don't strike me as nasty because I'm that kind of person--I get mad fast and make up fast." De Waal's studies have taught her that "we should work not so much at hiding our anger as at developing our ability to make up after we've shown it. And I've learned that conflicts may actually strengthen relationships.
"I wouldn't want to think of people as being real similar to rhesus monkeys, though," she says, "because rhesus are so hierarchical. If you had to be a monkey, you would never want to be the bottom-ranking rhesus. It's very stressful. You can be sleeping, and a high-ranking monkey will come up and bite you. Whenever there's a fight, the bottom-ranking monkey has to look around to see if someone's going to use her as a scapegoat."
Sometimes Luttrell watches a whole group of rhesus, noting at regular intervals what everyone is doing; at other times she focuses on one individual, recording everything it does. When she goes to a ball game at Milwaukee's County Stadium, Luttrell now frequently trains her binoculars on one player--the third baseman, say--for an inning or two, ignoring the pitcher and batter. "You have a different way of looking at baseball after you've watched monkeys," she says.
Last year, Luttrell, who is in the process of becoming certified as a teacher, was student teaching in a middle school. After two days, she could identify by name all 115 of the students in her five science classes. "Everyone wanted to know how I could do that," she says. "But if you can tell monkeys apart, it's easy to do it with people."
Spickles, the alpha male in one of the groups, is among her favorites. "I like how he manages to stay in charge with almost no strength left," she says. (Spickles is 28--old for a rhesus monkey.) "His agility is very low--he could never climb up on the ceiling anymore. And he's got visual problems. Yet he remains in charge, without beating anybody up much. It's amazing he can do that in a species like this. He makes it a point to interact with the young males, play with them a little. When he disapproves of something they've done, he goes up and bites them on their cheek pouch--not a hard bite, really a play one. It's like he's disciplining them.
"He's very good at knowing what to pay attention to and what to ignore," she says. "He doesn't interfere in matings of the other males, for instance. With alpha males, any matings in the public view should involve him, not anybody else. Well, Spickles knows how to not be where he can see anything. And he also knows how to make his matings very public. So even though he's old, he still has the form of a leader."
Every summer the University of Madison runs a College for Kids program, in which gifted fifth-graders take science and humanities courses designed for them. De Waal developed a class called "Monkey Behavior" for the program nine years ago. He taught it the first three years, and then Luttrell took over. At Vilas Zoo's monkey house, Luttrell gives the children a check sheet and asks them to pick a monkey to watch for five minutes. They have to check off what their animal is doing every minute--sleeping, eating, fighting, playing, huddling, sitting alone. The kids learn how to tell a playful chase from a threatening one. After five minutes, Luttrell has them choose another monkey, of a different sex, age, or rank. On the last day of the four-day session, they analyze the data they've gathered. "I always get raves from the kids," Luttrell says. "The people who run College for Kids have told me the class is one of their most popular. It just shows how interesting monkeys are to watch."
De Waal will be studying food sharing among chimpanzees when he begins work at the Yerkes primate center in Atlanta this summer.
"When you give a group of rhesus monkeys a limited amount of food, the dominant will take it and eat as much as he can," de Waal says. "It's different with chimpanzees. The dominant chimp may take it, but the others expect part of it. And if he doesn't share it, they have temper tantrums--they'll scream and roll around. And there usually is sharing: there are only a very few individuals who are stingy. Sharing among chimpanzees is much more in line with human systems of justice."
The study will be an extension of his work on reconciliation, he says. "When you provide the food to the chimpanzees, the inclination might be to compete over it. In order to share it, they have to overcome that competitive impulse. All these reassurance behaviors that play a role in reconciliation may help make sharing possible."
America's violence has always unnerved de Waal, so he's leaving Madison for the big city of Atlanta with some trepidation. "The threat of violence hardly exists in the Netherlands. Here, you hear about people shooting one another for no reason. You look at TV, the movies--the appetite Americans have for watching violence is amazing."
If Americans aren't good at settling problems peacefully, "maybe it's because in America's early years, there was a tremendous amount of space here," de Waal says. "People didn't have to work to resolve conflicts--they could just move somewhere else." In a cramped country like Holland, on the other hand, people had no choice but to learn how to square their differences; de Waal says that may be why the Dutch have become noted for their tolerance.
De Waal's research has inspired other ethologists to study reconciliation in a half-dozen additional primate species. Reconciliation behavior seems to be widespread indeed among primates, according to early results. De Waal hopes to see reconciliation studies of primates in the wild and of nonprimates. Studies of how humans make up might teach us something, too, he says. "There are thousands of studies on aggression and almost nothing on human reconciliation."
What he's learned from his work so far is that the more individuals depend on each other, the more they are willing to work to resolve differences and to make sure aggression doesn't get out of hand. To improve chances for world peace, he thinks we should try "to create greater interdependency, economically and politically, between countries. Isolation is the main threat, I think--if the United States would decide to stand on its own, for instance, that would be a very dangerous thing. When the Japanese buy a lot of things in the United States, I don't see that as a problem but as a good development.
"What we discover from studying animals may not always be of direct use," de Waal says, "but it helps put our own existence in perspective. We sometimes have an unrealistic picture of ourselves as being totally different from other animals. Ethology also helps satisfy our curiosity--which is the function of all science. Understanding the size and position of the Milky Way may not help us much in our daily lives; but still, it's something we would like to know."
"I've never seen Frans get mad," Luttrell says of her boss. In the nine years she and de Waal have worked together, she says, "we've never really fought about anything."
Despite the short fuse she says she has, it's understandable that Luttrell wouldn't start a fight with de Waal: subordinates, whether monkey, ape, or human, rarely precipitate disputes with dominants.
You might expect that de Waal would clash with coworkers and friends from time to time, though, especially considering his preaching that aggression may actually benefit relationships. But he doesn't. "I get upset maybe only with my wife," he says with a sheepish smile. "Oh, I do get upset with other people--but I don't express that. Some people get angry very easily and then regret it afterwards--and that's a situation I certainly would want to avoid if I can. I worry that if I would fight I would regret it. So I don't even go through the trouble of doing that."
For more information on Madison, see the Visitors' Guide in this issue.
Art accompanying story in printed newspaper (not available in this archive): photos/Lloyd DeGrane.