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1ONE Apes in the Family One can take the ape out of the jungle, but not the jungle out of the ape. This also applies to us, bipedal apes. Ever since our ancestors swung from tree to tree, life in small groups has been an obsession of ours. We can’t get enough of politicians thumping their chests on television, soap opera stars who swing from tryst to tryst, and reality shows about who’s in and who’s out. It would be easy to make fun of all this primate behavior if not for the fact that our fellow simians take the pursuit of power and sex just as seriously as we do. We share more with them than power and sex, though. Fellow-feeling and empathy are equally important, but they’re rarely mentioned as part of our biological heritage. We would much rather blame nature for what we don’t like in ourselves than credit it for what we do like. As Katharine Hepburn famously put it in The African Queen, “Nature, Mr. Allnut, is what we are put in this world to rise above.” This opinion is still very much with us. Of the millions of pages written over the centuries about human nature, none are as bleak as those of the last three decades—and none as wrong. We hear that we have selfish genes, that human goodness is a sham, and that we act morally only to impress others. But if all that people care about is their own good, why does a day-old baby cry when it hears another baby cry? This is how empathy starts. Not very sophisticated perhaps, but we can be sure that a newborn doesn’t try to impress. We are born with impulses that draw us to others and that later in life make us care about them. The old age of these impulses is evident from the behavior of our primate relatives. Truly remarkable is the bonobo, a little-known ape that is as close to us genetically as the chimpanzee. When a bonobo named Kuni saw a starling hit the glass of her enclosure at the Twycross Zoo in Great Britain, she went to comfort it. Picking up the stunned bird, Kuni gently set it on its feet. When it failed to move, she threw it a little, but the bird just fluttered. With the starling in hand, Kuni then climbed to the top of the tallest tree, wrapping her legs around the trunk so that she had both hands free to hold the bird. She carefully unfolded its wings and spread them wide, holding one wing between the fingers of each hand, before sending the bird like a little toy airplane out toward the barrier of her enclosure. But the bird fell short of freedom and landed on the bank of the moat. Kuni climbed down and stood watch over the starling for a long time, protecting it against a curious juvenile. By the end of the day, the recovered bird had flown off safely. The way Kuni handled this bird was unlike anything she would have done to aid another ape. Instead of following some hardwired pattern of behavior, she tailored her assistance to the specific situation of an animal totally different from herself. The birds passing by her enclosure must have given her an idea of what help was needed. This kind of empathy is almost unheard of in animals since it rests on the ability to imagine the circumstances of another. Adam Smith, the pioneering economist, must have had actions like Kuni’s in mind (though not performed by an ape) when, more than two centuries ago, he offered us the most enduring definition of empathy as “changing places in fancy with the sufferer.” The possibility that empathy is part of our primate heritage ought to make us happy, but we’re not in the habit of embracing our nature. When people commit genocide, we call them “animals.” But when they give to the poor, we praise them for being “humane.” We like to claim the latter behavior for ourselves. It wasn’t until an ape saved a member of our own species that there was a public awakening to the possibility of nonhuman humaneness. This happened on August 16, 1996, when an eight-year-old female gorilla named Binti Jua helped a three-year-old boy who had fallen eighteen feet into the primate exhibit at Chicago’s Brookfield Zoo. Reacting immediately, Binti scooped up the boy and carried him to safety. She sat down on a log in a stream, cradling the boy in her lap, giving him a few gentle back pats before taking him to the waiting zoo staff. This simple act of sympathy, captured on video and shown around the world, touched many hearts, and Binti was hailed as a heroine. It was the first time in U.S. history that an ape figured in the speeches of leading politicians, who held her up as a model of compassion. THE HUMAN JANUS HEAD That Binti’s behavior caused such surprise among humans says a lot about the way animals are depicted in the media. She really did nothing unusual, or at least nothing an ape wouldn’t do for any juvenile of her own species. While recent nature documentaries focus on ferocious beasts (or the macho men who wrestle them to the ground), I think it’s vital to convey the true breadth and depth of our connection with nature. This book explores the fascinating and frightening parallels between primate behavior and our own, with equal regard for the good, the bad, and the ugly. We are blessed with two close primate relatives to study, and they are as different as night and day. One is a gruff-looking, ambitious character with anger-management issues. The other is an egalitarian proponent of a free-spirited lifestyle. Everyone has heard of the chimpanzee, known to science since the seventeenth century. Its hierarchical and murderous behavior has inspired the common view of humans as “killer apes.” It’s our biological destiny, some scientists say, to grab power by vanquishing others and to wage war into perpetuity. I have witnessed enough bloodshed among chimpanzees to agree that they have a violent streak. But we shouldn’t ignore our other close relative, the bonobo, discovered only last century. Bonobos are a happy-go-lucky bunch with healthy sexual appetites. Peaceful by nature, they belie the notion that ours is a purely bloodthirsty lineage. It is empathy that allows bonobos to understand each other’s needs and desires and to help achieve them. When the two-year-old daughter of a bonobo named Linda whimpered at her mother with pouted lips, it meant that she wanted to nurse. But this infant had been in the San Diego Zoo’s nursery and was returned to the group long after Linda’s milk had dried up. The mother understood, though, and went to the fountain to suck her mouth full of water. She then sat in front of her daughter and puckered her lips so that the infant could drink from them. Linda repeated her trip to the fountain three times until her daughter was satisfied. We adore such behavior—which is itself a case of empathy. But the same capacity to understand others also makes it possible to hurt them deliberately. Both sympathy and cruelty rely on the ability to imagine how one’s own behavior affects others. Small-brained animals, such as sharks, certainly can hurt others, but they do so without the slightest idea of what others may feel. The brains of apes, on the other hand, are one-third the size of ours, making them sufficiently complex for cruelty. Like boys throwing rocks at ducks in a pond, apes sometimes inflict pain for fun. In one game, juvenile lab chimpanzees enticed chickens behind a fence with bread crumbs. Each time the gullible chickens approached, the chimps hit them with a stick or poked them with a sharp piece of wire. This Tantalus game, which the chickens were stupid enough to play along with (although we can be sure it was no game to them), was invented by the chimps to fight boredom. They refined it to the point that one ape would be the baiter, another the hit man. Apes are so like us that they’re known as “anthropoids,” from the Latin for “humanlike.” To have two close relations with strikingly different societies is extraordinarily instructive. The power-hungry and brutal chimp contrasts with the peace-loving and erotic bonobo—a kind of Dr. Jekyll and Mr. Hyde. Our own nature is an uneasy marriage of the two. Our dark side is painfully obvious: An estimated 160 million people in the twentieth century alone lost their lives to war, genocide, and political oppression—all due to the human capacity for brutality. Even more chilling than such incomprehensible numbers are more personal expressions of human cruelty, such as the appalling incident in a small Texas town in 1998 in which three white men offered a forty-nine-year-old black man a ride. Instead of taking him home, they drove him to a deserted spot and beat him, then tied him to their truck and dragged him several miles along an asphalt road, tearing off his head and right arm. We are capable of such savagery despite, or perhaps precisely because of, our ability to imagine what others feel. On the other hand, when that same ability is combined with a positive attitude, it prompts us to send food to starving people, make valiant efforts to rescue complete strangers (such as during earthquakes and fires), cry when someone tells a sad story, or join a search party when a neighbor’s child is missing. With both cruel and compassionate sides, we stand in the world like a Janus head, our two faces looking in opposite directions. This can confuse us to the point that we sometimes oversimplify who we are. We either claim to be the “crown of creation” or depict ourselves as the only true villains. Why not accept that we are both? These two aspects of our species correspond to those of our closest living relatives. The chimpanzee demonstrates the violent side of human nature so well that few scientists write about any other side at all. But we are also intensely social creatures who rely on one another and actually need interaction with other people to lead sane and happy lives. Next to death, solitary confinement is our most extreme punishment. Our bodies and minds are not designed for lonely lives. We become hopelessly depressed in the absence of human company, and our health deteriorates. In one recent medical study, healthy volunteers exposed to cold and flu viruses got sick more easily if they had fewer friends and family around them. This need for connection is naturally understood by women. In mammals, parental care cannot be separated from lactation. During the 180 million years of mammalian evolution, females who responded to their offspring’s needs outreproduced those who were cold and distant. Having descended from a long line of mothers who nursed, fed, cleaned, carried, comforted, and defended their young, we should not be surprised by gender differences in human empathy. They appear well before socialization: The first sign of empathy—crying when another baby cries—is already more typical in girl babies than boy babies. And later in life empathy remains more developed in females than in males. This is not to say that men lack empathy or don’t need to connect with others, but they seek it more from women than from other men. A long-term relationship with a woman, such as marriage, is the most effective way for a man to add years to his life. The flip side of this picture is autism—an empathy disorder that keeps us from connecting with others—which is four times more common in males than females. The empathic bonobos regularly put themselves into someone else’s shoes. At the Georgia State University Language Research Center in Atlanta, a bonobo called Kanzi has been trained to communicate with people. He has become a bonobo celebrity, known for his fabulous understanding of spoken English. Realizing that some of his fellow apes do not have the same training, Kanzi occasionally adopts the role of teacher. He once sat next to Tamuli, a younger sister who has had minimal exposure to human speech, while a researcher tried to get Tamuli to respond to simple verbal requests; the untrained bonobo didn’t respond. As the researcher addressed Tamuli, it was Kanzi who began to act out the meanings. When Tamuli was asked to groom Kanzi, he took her hand and placed it under his chin, squeezing it between his chin and chest. In this position, Kanzi stared into Tamuli’s eyes with what people interpreted as a questioning gaze. When Kanzi repeated the action, the young female rested her fingers on his chest as if wondering what to do. Kanzi understands perfectly well whether commands are intended for him or for others. He was not carrying out a command intended for Tamuli—he actually tried to make her understand. Kanzi’s sensitivity to his sister’s lack of knowledge, and his kindness in teaching her, suggest a level of empathy found, as far as we know, only in humans and apes. WHAT’S IN A NAME? In 1978, I first saw bonobos up close at a Dutch zoo. The label on the cage identified them as “pygmy chimpanzees,” implying they were just a smaller version of their better-known cousins. But nothing could be further from the truth. A bonobo is physically as different from a chimpanzee as a Concorde is from a Boeing 747. Even chimps would have to admit that the bonobo has more style. A bonobo’s body is graceful and elegant, with piano-player hands and a relatively small head. The bonobo has a flatter, more open face with a higher forehead than the chimpanzee. A bonobo’s face is black, its lips are pink, its ears small, and its nostrils wide. Females have breasts; they are not as prominent as in our species, but definitely A-cup compared to the flat-chested other apes. Topping it all off is the bonobo’s trademark hairstyle: long black hair neatly parted in the middle. The biggest difference between the two apes is body proportion. Chimps have large heads, thick necks, and broad shoulders—they look as if they work out in the gym every day. Bonobos have a more intellectual appearance, with slim upper bodies, narrow shoulders, and thin necks. A lot of their weight is in their legs, which are longer than a chimp’s. The result is that when knucklewalking on all fours, the chimp’s back slopes down from powerful shoulders, whereas the bonobo’s remains fairly horizontal because of its elevated hips. When standing or walking upright, a bonobo seems to straighten its back better than a chimp, giving the bonobo an eerily humanlike posture. For this reason, bonobos have been compared to “Lucy,” our Australopithecus ancestor. The bonobo is one of the last large mammals to be discovered by science. The discovery took place in 1929, not in a lush African habitat, but in a colonial Belgian museum following the inspection of a small skull thought to have belonged to a juvenile chimp. In immature animals, however, the sutures between skull bones ought to be separated. In this skull, they were fused. Concluding that it must have belonged to an adult chimp with an unusually small head, Ernst Schwarz, a German anatomist, declared that he had stumbled upon a new subspecies. Soon the anatomical differences were considered important enough to elevate the bonobo to the status of an entirely new species: Pan paniscus. A biologist who had been a student with Schwarz in Berlin told me how Schwarz’s peers used to make fun of him. Schwarz not only claimed there were two chimp species, but also that there were three elephant species. Everyone knew that there was only one of the first and two of the second. Their standard line about der Schwarz was that he knew “everything and more.” As it turns out, Schwarz was right. The African forest elephant was recently confirmed as a separate species, and Schwarz is known as the official discoverer of the bonobo —the sort of honor scientists are willing to die for. The bonobo’s genus name, Pan, derives appropriately enough from the Greek forest god with a human torso and the legs, ears, and horns of a goat. Playfully lecherous, Pan loves to frolic with nymphs while playing the shepherd’s (or pan) flute. The chimpanzee belongs to the same genus. The bonobo’s species name, paniscus, means “diminutive,” whereas the chimp’s species name, troglodytes, means “cave dweller.” With the bonobo being called a small goat deity and the chimp a grotto goat deity, these are curious epithets indeed. The name “bonobo” probably derives from a misspelling on a shipping crate from “Bolobo,” a town on the Congo River (although I have also heard that “bonobo” means “ancestor” in an extinct Bantu language). In any case, the name has a happy ring to it that befits the animal’s nature. Primatologists jokingly employ it as a verb, as in “We’re gonna bonobo tonight,” the meaning of which will soon become clear. The French refer to bonobos as “Left Bank chimpanzees”—a name that summons up images of an alternative lifestyle— since they live on the south bank of the westward streaming Congo River. This mighty river, which in places is ten miles wide, permanently separates bonobos from the chimpanzee and gorilla populations to the north. Despite the bonobo’s previous name, “pygmy chimpanzee,” they are not much smaller than chimpanzees. The average adult male bonobo weighs ninety-five pounds and the average female eighty pounds. What struck me most while watching my first bonobos was how sensitive they seemed. I also discovered some habits that shocked me. I witnessed a minor squabble over a cardboard box, in which a male and female ran around and pummeled each other until all of a sudden the fight was over and they were making love! I had been studying chimps, which never switch so easily from fighting to sex. I thought this bonobo behavior was an anomaly or that I had missed something that could explain the sudden change of heart. But it turned out that what I had seen was perfectly normal for these Kama Sutra primates. I learned this much later, after I had begun working with bonobos at the San Diego Zoo. Information on wild bonobos had been trickling in over the years from Africa, which added to our knowledge about this mysterious cousin. Bonobos are native to a relatively small area, about the size of England, in the Democratic Republic of the Congo (formerly Zaire) where they live in dense, humid swamp forest. When they enter a clearing where field workers leave sugarcane, the males arrive first. They hurry to collect handfuls of stalks so that they have their share before any females show up. When the females arrive, their entrance is accompanied by lots of sex among everybody and the inevitable appropriation of the best food by the older matriarchs. The same is true for the zoo colonies that I’ve studied, which are invariably ruled by an older female. This is surprising given that male and female bonobos differ as much in size as humans do, with the average female bonobo weighing 85 percent as much as the average male. On top of this, male bonobos have sharp canine teeth, which the females lack. So how do the females maintain control? The answer is solidarity. Take Vernon, a male bonobo at the San Diego Zoo, who used to rule a small group that included one female, Loretta, who was his mate and friend. This was the only instance I have ever seen of a bonobo group run by a male. At the time, I thought this was normal: after all, male dominance is typical of most mammals. But Loretta was relatively young, and she was the only female. As soon as a second female was added to the group, the power balance shifted. The first thing Loretta and the other female did upon meeting was have sex. The pattern is known by experts as genito-genital-(or GG-) rubbing, but I have also heard it called, more colorfully, the “hokahoka.” One female wrapped her arms and legs around the other and clung to her the way an infant bonobo attaches itself to its mother’s belly. Facing each other, the two then pressed their vulvas and clitorises together, rubbing them sideways in a rapid rhythm. They had big grins on their faces and squealed loudly, leaving little doubt about whether apes know sexual pleasure. Sex between Loretta and her new female friend became more and more common, spelling the end of Vernon’s rule. Months later the typical scene at feeding time was the females having sex and then together claiming all the food. The only way for Vernon to get any food was by begging with outstretched hand. This is also typical among wild bonobos, where females control the food supply. Compared with the male-centered chimpanzee, the female-centered, erotic, and peaceable bonobo offers a fresh way of thinking about human ancestry. Its behavior is hardly consistent with the popular image of our forefathers as bearded cavemen dragging women around by their hair. Not that things were necessarily the other way around, but it is good to be clear on what we know and don’t know. Behavior doesn’t fossilize. This is why speculations about human prehistory are often based on what we know about other primates. Their behavior indicates the range of behavior our ancestors may have shown. And the more we learn about bonobos, the more this range expands. MAMA’S BOYS Not too long ago, I spent a typical day at the San Diego Zoo with two old friends, Gale Foland and Mike Hammond, both veteran ape keepers. This is not a job for everyone. It’s impossible to deal with the needs and reactions of apes without tapping the same emotional reservoir we use to deal with fellow human beings. Keepers who fail to take apes seriously will never get along with them, and those who take them too seriously will succumb to the web of intrigues, provocations, and emotional blackmail that suffuses every ape group. In an area away from the public, we leaned over a balustrade looking down on a spacious, grassy enclosure. The air carried the unique pungent smell of gorillas. Earlier this morning, Gale had introduced a five-year-old female named Azizi, whom he had raised himself, to the enclosure. Azizi found herself in a group with a new male, Paul Donn, a gargantuan character who is leaning against the wall. Occasionally, he charges around the enclosure, beating his chest, to impress upon the gathering of females that he is in control, or at least would like to be. Female gorillas, especially the older ones, tend to disagree: they sometimes band together to chase him around “to keep him in line,” as Gale says. But for the moment Paul Donn is calm, and we see Azizi shuffle closer and closer toward him. The male acts as if he fails to notice, tactfully inspecting his toes and never looking straight at the nervous gorilla girl. Each time Azizi gets a little bit nearer, she glances up at Gale, her adoptive parent. She locks her eyes into his. Gale nods and says such things as “Go on, don’t be scared.” This is easy for him to say: Paul Donn is probably five times Azizi’s weight, all of it muscles. But Azizi is irresistibly attracted. These gorillas are known for their intelligence. Gorillas are not supposed to use tools: in the wild they never do. But three gorillas at the zoo have found a new way to get at the tasty leaves of the fig trees. They are prevented from climbing the trees by hot wire, but get around this by picking up one of the many branches lying around, standing up on two legs and flinging it into a tree. The branch usually comes back down with some of the foliage. One female was seen breaking a long stick in two and using the more suitable piece—an important step, as it showed that gorillas are capable of modifying their tools. Today, an incident takes place involving the same hot wire. It’s the sort of scene that catches my eye. One older resident female has learned to reach under the wire without getting shocked to feed on weeds that grow beyond the wire. Right next to her sits a new female, who, Gale tells me, has just recently been shocked for the first time. It was a nasty experience for her, resulting in screaming and frantic handshaking. The new female has befriended the other and now sits watching her do exactly what had caused her so much pain. As soon as she sees her friend reach under the wire, she jumps behind her and starts pulling at her. She wraps an arm around her middle and tries to move her away from the electric fence. But her older friend doesn’t budge; instead, she continues to reach. After some time, the new female sits back, watching intently, while wrapping both of her arms tightly around herself. She seems to be bracing herself for the shock she believes the other will get. “Changing places in fancy” indeed. Like chimpanzees and bonobos, gorillas are known as great apes. There are only four great ape species, the fourth one being the orangutan. Apes are primates that are large and lacking tails. Both traits set the family of humans and apes—known as the Hominoids—apart from the monkeys. Apes should therefore never be confused with monkeys (there is no better way to insult an ape expert than to say that you love his monkeys!), and “primate” is the more inclusive label, as it also applies to us. Among the apes, our closest kin are chimps and bonobos, neither one of which is closer to us than the other. Yet this doesn’t prevent primatologists from hotly debating which one is the best ancestral human model. We all derive from a single forebear, and one species may have retained more of its traits than the other, making it more relevant to human evolution. But it’s impossible right now to determine which one. Not surprisingly, chimp experts generally vote for the chimpanzee and bonobo experts for the bonobo. Since gorillas split off from our evolutionary branch slightly before chimps and bonobos, it’s been argued that whichever ape is more like the gorilla deserves to be called the original type. But who says that gorillas themselves resemble our last common ancestor? They have had plenty of time to change, too —over seven million years, in fact. What we are looking for instead is the ape that has changed the least over time. Takayoshi Kano, the premier expert on wild bonobos, has argued that since bonobos never left the humid jungle—whereas chimpanzees did so partially and our own ancestors completely—bonobos probably have encountered fewer pressures to change and may therefore look most like the forest ape from which we all descend. American anatomist Harold Coolidge famously speculated that the bonobo “may approach more closely to the common ancestor of chimpanzees and man than does any living chimpanzee.” Adaptation to life in the trees is obvious from the way bonobos use their bodies, which by human standards is rather unusual. Their feet serve as hands. They grasp things with their feet, gesture with them during communication, and clap them together to attract attention. Apes are sometimes called “quadrupedal” (four-footed), but bonobos might be better called “quadrumanual” (four-handed). They are more gymnastic than any other ape, jumping, brachiating, and flipping around in the trees with unbelievable agility. They walk along a suspended rope on two legs as if on terra firma. These acrobatic talents are practical for apes who have never been forced, not even partially, out of the forest, and who have hence never had to compromise their tree-dwelling ways. That bonobos are more arboreal than chimps is clear from a comparison of reactions to seeing scientists for the first time in the wild: Chimps drop straight out of the tree they are in and flee by running over the ground. Bonobos, on the other hand, flee through the tree canopy and only descend to the forest floor once they’re far away. Tree of origin of humans and the four great apes based on DNA comparisons. Data points indicate how many millions of years ago species diverged. Chimpanzees and bonobos form a single genus: Pan. The human lineage diverged from the Pan ancestor about 5.5 million years ago. Some scientists feel that humans, chimpanzees, and bonobos are close enough to form a single genus: Homo. Since bonobos and chimpanzees split from each other after they split from us, about 2.5 million years ago, both are equally close to us. The gorilla diverged earlier, hence it is more distant from us, as is the only Asian great ape, the orangutan. I expect the debate about which ape most resembles the last common ancestor to go back and forth for a while, but for the moment, let us just say that chimps and bonobos are equally relevant for human evolution. The gorilla is set apart from both them and us by its enormous sexual dimorphism—the size difference between males and females—and the social system that goes with that: a single male monopolizing a harem of females. For simplicity’s sake, I will mention gorillas only occasionally while we explore the similarities and differences among bonobos, chimps, and ourselves. We do not wait around to see what happens between Azizi and Paul Donn. Undoubtedly, the two will make contact, but it could take hours, even days. The keepers realize that it will change Azizi’s attitude forever: she will never be the same dependent little gorilla that Gale fed with a bottle and carried on his back until she grew too heavy. Her new destiny will be to live in this group, be around a big male of her own kind, and perhaps raise offspring. We walk by the bonobos, where Loretta greets me with shrill hoots. Even though my research time at this zoo was almost twenty years ago, she still knows me: recognition is permanent. I cannot imagine ever forgetting a face that I saw every day over a period of time, so why should it be different for Loretta? And her hoots are distinctive. Bonobo calls are unmistakable: The easiest way to tell chimps and bonobos apart is just by listening to them. The low huu-huu sound of the chimpanzee is absent in the bonobo. Bonobo voices are so high pitched (more like heehee) that when the Hellabrunn Zoo in Munich received its first bonobos, the director almost sent them back. He hadn’t yet looked under the cloth covering the crates from Bolobo and couldn’t believe that the sounds he heard came from apes. Loretta presents her ballooning genitals, staring at me upside-down though her legs, invitingly waving an arm. I wave back while asking Mike about one of the males who’s not out. Mike takes me to the night quarters. The male sits indoors with a young female to keep him company. The female is clearly annoyed each time Mike turns to talk to me. What is this stranger doing here, and why is Mike not giving her his full attention? She tries to grab me through the bars. The male keeps his distance, but presents his back, then his belly to Mike for touching, while showing—as any male bonobo would under such circumstances—an impressive erection. For both male and female bonobos, there is no dividing line between sexuality and affection. This male needs to be kept out of the bonobo group due to his low rank. Even though he’s fully grown, he’s unable to defend himself against an entire group of females. Female hostility against males is a growing problem among bonobos in zoos. In the past, the zoo community made a fundamental mistake by moving male bonobos around. If they had to send apes to another zoo for breeding, they always chose males. While this works well for most animals, it is a disaster for male bonobos. In nature, bonobo females do all the migrating, leaving their home group at puberty. Males stay put, enjoying the company and protection of their mothers. Males with influential mothers rise in the hierarchy and are tolerated around food. Zoos have learned the hard way that they need to follow this example. Unfortunately, the male in question had been brought in from the outside. Being real mama’s boys, males fare best in the group in which they were born. So aggression is by no means absent among bonobos. When females attack, things get ugly. From a screaming ball of arms and legs, it is invariably the male who emerges with injuries. Even though bonobos are usually great conciliators, they have these skills for a good reason: they are not above fighting. The bonobo provides a compelling example of social harmony precisely because underlying tensions remain visible. This paradox applies to us as well. In the same way that the ultimate test of a ship is how it holds up in a storm, we only fully trust a relation if it has survived occasional conflict. After witnessing a few more sexual encounters among the bonobos, Mike cannot resist bringing up the recent claim of a local scientist that the zoo’s bonobos rarely have sex, perhaps only a couple of times per year. Could it be that bonobos do not deserve their sexy reputation? Standing back outside among the public, we joke that since today we have counted six sexual encounters in just two hours, this must mean that we have gathered about two years’ worth of observations. For a moment, I forget that Mike and Gale have their uniforms on, meaning that everyone around us is listening in. A bit too loudly, I boast about my earlier study, “When I was here, I had seven hundred sexual encounters in a single winter.” A man standing next to us grabs his young daughter by the arm and rushes away. Sometimes bonobo sex is subtle. One young female tries to walk past an even younger male who is blocking her path on a branch. The male fails to move out of the way—perhaps he is afraid of falling—whereupon the female places her teeth on his hand, which holds on to the branch, making matters worse. But instead of using force, she then turns around and rubs her clitoris against his arm. They are both immature, but this is the bonobo way of resolving conflict, a tactic that begins early in life. Following this contact, the female calmly climbs over the male and continues along the branch. Upon returning home from San Diego, I am struck by the contrast with chimpanzees. I work with about forty chimps outdoors at the Field Station of the Yerkes National Primate Research Center, near Atlanta. I have known these apes for a long time, and I see them as distinct personalities. They know me equally well and pay me the one compliment every researcher craves, which is that they treat me like furniture. I walk up to the fence to say hello to Tara, the three-yearold little daughter of Rita, who sits high up in a climbing structure. Rita briefly glances down at us, then continues grooming her own mother, Tara’s grandmother. If a stranger had merely walked by, Rita, who is extremely protective, would have immediately jumped down to pick up her daughter. I feel honored by her lack of interest. I notice a deep, fresh gash on the upper lip of Socko, the second ranking male. Only one other male can have done this: Bjorn, the alpha male. Bjorn is smaller than Socko, but he’s extremely smart, high-strung, and mean. He keeps the other apes under control by fighting dirty. This is the conclusion we have come to over the years, from seeing Bjorn’s combat technique and the scars he leaves on his victims in unusual places, such as the belly or scrotum. Socko—a large, lumbering “ham”—cannot compete, so he must live under this little dictator. But luckily for Socko, his younger brother, who is in the midst of his final growth spurt, is eager to hang out with him. This is bound to create trouble for Bjorn very soon. Here at Yerkes, we’re in the thick of male power politics, the never-ending saga of chimpanzee society. Ultimately these battles are about females, which means that the fundamental difference between our two closest relatives is that one resolves sexual issues with power, while the other resolves power issues with sex. A VENEER OF CIVILIZATION As I opened the newspaper on a plane ride from Chicago to Charleston, South Carolina, the first thing that caught my eye was the headline “Lili to Hit Charleston.” This was disconcerting as Lili was a major hurricane, and the devastation of Hugo the year before was still fresh in everybody’s memories. Lili swung away from Charleston, however, and the storm I ended up in was merely academic. The conference I attended was about world peace and peaceful human relations. I went there to present my work on primate conflict resolution. It is always fun to speculate why people are drawn to certain fields, but peace research attracts its share of hotheads. At the meeting, two prominent peace advocates got into a shouting match, something having to do with the first referring to studies of Eskimos and the second accusing him of colonialist if not racist attitudes, since these people ought to be called Inuit. According to the book Never in Anger, Inuit go to extreme lengths to avoid exchanges that even remotely resemble hostility. Anybody who raises his or her voice risks being ostracized, which is a life-threatening punishment in their environment. Some of us at the meeting surely would have been put out on the ice. Being Westerners, nonconfrontation was not in our script. I could already see another newspaper headline, something to the effect of “Peace Conference Ends in Fistfight.” It is the only academic event at which I have seen fully grown men walk out of the room slamming doors like little children. Amid all this grandstanding, some dared wonder, with deep scholarly frowns on their faces, if human and ape behavior were truly comparable. On the other hand, I have attended many meetings of the Aggression Club, a group of academics in the Netherlands, which were always civil and calm. Though only a graduate student at the time, I was allowed to join psychiatrists, criminologists, psychologists, and ethologists who regularly came together to discuss aggression and violence. In those days, evolutionary views invariably revolved around aggressiveness, as if our species had no other behavioral tendencies to speak of. It was like a discussion about pit bulls in which the main topic is always how dangerous these dogs are. What makes humans different from pit bulls, however, is that we have not been selectively bred to fight. Our jaw pressure is miserable, and our brains certainly would not need to be the size they are if the only trait that mattered was the killing of others. But in the postwar era, human aggressiveness was front and center of every debate. With its gas chambers, mass executions, and willful destruction, World War II was human behavior at its worst. Moreover, when the Western world took stock after the dust had settled, it was impossible to ignore the savagery that had been committed in the heart of Europe by otherwise civilized people. Comparisons with animals were ubiquitous. Animals lack inhibitions, the argument went. They lack culture, so it must have been something animal-like, something in our genetic makeup that had burst through the veneer of civilization and pushed human decency aside. This “veneer theory,” as I call it, became a dominant theme in the postwar discussion. Deep down, we humans are violent and amoral. A stream of popular books explored this issue by proposing that we have an uncontainable aggressive drive that seeks an outlet in warfare, violence, and even sports. Another theory was that our aggressiveness is novel, that we are the only primates that kill their own kind. Our species never had the time to evolve the appropriate inhibitions. As a result, we don’t have our fighting instinct under control as much as “professional predators” like wolves or lions. We’re stuck with a violent temper that we’re ill-equipped to master. It is not hard to see the beginnings here of a rationalization of human violence in general and the Holocaust in particular, and it certainly did not help that the leading voice of the time spoke German. Konrad Lorenz, a worldrenowned Austrian expert on fish and geese, was the great defender of the idea that aggression is in our genes. Killing became humanity’s “mark of Cain.” Across the Atlantic, a similar view was promoted by Robert Ardrey, an American journalist inspired by speculations that Australopithecus must have been a carnivore who swallowed his prey alive, dismembering them limb from limb, slaking his thirst with warm blood. Drawn from studies of a few skull bones, this was an imaginative conclusion, but Ardrey based his killer ape myth on it. In African Genesis, he painted our ancestor as a mentally deranged predator upsetting the precarious balance of nature. In Ardrey’s demagogic prose, “We were born of risen apes, not fallen angels, and the apes were armed killers besides. And so what shall we wonder at? Our murders and massacres and missiles, and our irreconcilable regiments?” It’s hard to believe, but the next wave of pop biology managed to go beyond this. At the same time that Ronald Reagan and Margaret Thatcher preached that greed was good for society, good for the economy, and certainly good for those with anything to be greedy about, biologists published books in support of these views. Richard Dawkins’s The Selfish Gene taught us that since evolution helps those who help themselves, selfishness should be looked at as a driving force for change rather than a flaw that drags us down. We may be nasty apes, but it makes sense that we are, and the world is a better place for it. A tiny problem—pointed out to no avail by nitpickers—was the misleading language of this genre of books. Genes that produce successful traits spread in the population and hence promote themselves. But to call this “selfish” is nothing but a metaphor. A snowball rolling down the hill gathering more snow also promotes itself, but we generally don’t call snowballs selfish. Taken to its extreme, the everything-is-selfishness position leads to a nightmarish world. Having an excellent nose for shock value, these authors haul us to a Hobbesian arena in which it’s every man for himself, where people show generosity only to trick others. Love is unheard of, sympathy is absent, and goodness a mere illusion. The best-known quote of those days, from biologist Michael Ghiselin, says it all: “Scratch an altruist, and watch a hypocrite bleed.” We should be happy that this dark, forbidding place is pure fantasy, that it differs radically from the actual world in which we laugh, cry, make love, and fawn over babies. Authors of this fiction realize this and sometimes confide that the human condition is not as bad as they make it sound. The Selfish Gene is a good example. Having argued that our genes know what is best for us, that they program every little wheel of the human survival machine, Dawkins waits until the very last sentence of his book to reassure us that, in fact, we are welcome to chuck all those genes out the window: “We, alone on earth, can rebel against the tyranny of the selfish replicators.” And so the end of the twentieth century emphasized our need to rise above nature. This view was advertised as Darwinian, even though Darwin had nothing to do with it. Darwin believed, as I do, that our humaneness is grounded in the social instincts that we share with other animals. This is obviously a more optimistic view than the one proclaiming that we “alone on earth” can overcome our basic instincts. In the latter view, human decency is no more than a thin crust —something we invented rather than inherited. And each time we do anything less than honorable, veneer theorists will remind us of the dreadful core underneath: “See, there’s human nature!” OUR DEMONIC FACE The opening scene of Stanley Kubrick’s 2001: A Space Odyssey captured in one dazzling image the idea that violence is good. After a fight breaks out among hominids, in which one bludgeons another with a zebra femur, the weapon is flung triumphantly into the air where millennia later it turns into an orbiting spacecraft. Equating aggression with progress underlies the so-called “Out of Africa” hypothesis, which posits that we’ve gotten to where we are today through genocide. When bands of Homo sapiens migrated out of Africa, they advanced into Eurasia by murdering all other bipedal apes they ran into, including the species most similar to them, the Neanderthals. Our bloodthirstiness is the centerpiece of books with titles like Man the Hunter, Demonic Males, The Imperial Animal, and The Dark Side of Man, which mostly feature the chimpanzee as our ancestral model—the male chimpanzee. Like the bombshells in early James Bond movies, females are what males fight over, but apart from being mates and mothers, they barely enter the story. Males do all the deciding and fighting—and, by implication, most of the evolving. But even though the chimpanzee has come to represent the demonic face of our Janus head, it has not always been this way. Around the time that Lorenz and Ardrey were highlighting our “mark of Cain,” wild chimps seemed to be doing little else than moving lazily from tree to tree collecting fruit. Adversaries of the killer ape view—and they were plentiful—used this information to their advantage. They freely quoted Jane Goodall, who in 1960 had started her work at Gombe Stream in Tanzania. At the time, Goodall still presented chimps as the noble savages of French philosopher Jean-Jacques Rousseau: self-sufficient loners with no need to connect or to compete with one another. Chimps in the jungle traveled alone or in small “parties” that changed composition all the time. The only permanent bonds were those between mother and dependent offspring. No wonder people thought of apes as living in Eden. The first correction of these impressions came in the 1970s from Japanese scientists who studied chimpanzees a little south of Gombe, in the Mahale Mountains. They had serious doubts about the “individualistic” bias of American and European researchers. How could an animal so close to us have no society to speak of? They found that even though chimps hang out with different companions every day, they’re all members of a single community that is separate from other communities. The second correction was to the reputation of wild chimpanzees as peaceful, which some anthropologists used as an argument against an innately aggressive human nature. Two reality checks appeared. First, we heard that chimps hunt monkeys, smash in their skulls, and eat them alive. This made them carnivores. Then, in 1979, the posh pages of National Geographic reported that these apes also kill each other, sometimes consuming their victims. This made them both murderers and cannibals. The report showed sketches of male chimps stalking unsuspecting enemies across the border of their territory, surrounding them, and brutally beating them to death. At first, this news trickled in from only a few sources, but soon the trickle turned into a steady stream that was impossible to ignore. The picture became indistinguishable from that of the killer ape. We now knew that chimps hunt to kill and live in communities that are at war with one another. In a later book, Goodall relates how she broke this news to a group of academics, some of whom held out hope of eliminating human aggression through education and improved television programming. Her message that we are not the only aggressive primates was unwelcome: Shocked colleagues begged her to downplay the evidence or even not to publish it. Others felt the camp at Gombe, where investigators dispensed bananas—an unnatural, highly nutritious food—had fostered pathological levels of aggression. Competition at the campsite was indeed well documented, but the most serious fighting had taken place far away from there. Goodall resisted her critics: “Certainly, I felt strongly it was better to face up to the facts, however unsettling, than to live in a state of denial,” she said. The banana critique failed to stick: warfare is now also known from African sites without any provision of extra food. The simple truth is that brutal violence is part of the chimp’s natural makeup. They don’t need to show it—some chimpanzee communities indeed seem rather peaceful—but they can and often do. This strengthens the killer ape theory in one way, but it also undermines it. Lorenz and Ardrey claimed that humans stood alone in their use of lethal force, whereas observations of not only chimps but also hyenas, lions, langurs, and a long list of other animals have since made it clear that killing one’s own kind, while infrequent, is in fact widespread. Ed Wilson, the sociobiologist, concluded that by the time a particular animal is observed for more than a thousand hours, scientists will see mortal combat. Here, he spoke as an expert on ants, a group of insects that raids and kills on a massive scale. In Wilson’s words, “Alongside ants, which conduct assassinations, skirmishes, and pitched battles as routine business, men are all but tranquilized pacifists.” With the discovery of the chimp’s dark side—“paradise lost”—Rousseau went out the door and Hobbes came in. The violence of apes surely meant that we are programmed to be ruthless. Combined with evolutionary biologists’ claim that we are genetically selfish, everything clicked into place. There was now a coherent, irrefutable view of humanity. Look at the chimpanzee, the argument went, and you will see what kind of monsters we truly are. Chimps thus fortified the idea of a nasty human nature despite the fact that, without too much trouble, they could equally well have countered it. After all, chimp violence is far from an everyday occurrence: it took scientists decades to reveal it. Unhappy with the one-sided impact of her discoveries, Goodall herself made valiant efforts to illuminate the gentler side of chimpanzees, their compassion even, but to no avail. Science had made up its mind: once a murderer, always a murderer. Chimps may be violent, but at the same time their communities have powerful checks and balances. This became clear to me one day at the Arnhem Zoo in the Netherlands when we stood in nail-biting anticipation at the edge of a moat surrounding a forested island. We were worried about a tiny newborn chimpanzee known as Roosje, Dutch for “little rose.” Roosje had been adopted by Kuif. Having no milk of her own, Kuif had been trained to give Roosje the bottle. The plan had worked beyond our wildest dreams. A minor feat for an ape was a giant success for us, or so we felt. But now we were reintroducing the mother with her new daughter to the world’s largest zoo colony of chimpanzees, one that included four dangerous adult males. To intimidate their rivals, males tend to charge about with all their hair on end so that they look large and threatening. Unfortunately, this was the state that Nikkie, the colony’s fearless leader, was in. Male chimps have a ferocious temper and are so strong that they can overpower humans easily; when angry they are beyond our control. So Roosje’s fate was in the apes’ hands. In the morning, we had paraded Kuif past all of the night cages to gauge the group’s reaction. They all knew Kuif, but Roosje was new. When Kuif walked by the male cage, something caught my attention. Nikkie was grabbing underneath her through the bars, causing her to jump away with a sharp yelp. His target seemed to be the spot where Roosje was clinging to Kuif’s belly. Since only Nikkie acted this way, I decided to do the group introduction in stages, putting Nikkie at a disadvantage by releasing him last. The main thing to avoid was letting Kuif find herself alone with him. I counted on her protectors in the group. In the wild, chimps occasionally kill infants of their own species. Some biologists’ theories about these acts of infanticide assume that males compete over the fertilization of females. This would explain their constant jockeying for position as well as the killing of infants that are not their own. Nikkie may have seen Roosje as an outside infant, one that could not possibly have been fathered by him. This was hardly reassuring as it meant that we might witness one of those gruesome scenes reported from the field. Roosje might be torn to shreds. Since I had been holding her for weeks, helping Kuif to feed her, and feeding her myself, I was far from the dispassionate observer I normally like to be. Once on the island, most colony members greeted Kuif with an embrace, stealing glances at the baby. Everyone seemed to be keeping a nervous eye on the door behind which Nikkie sat waiting. Some youngsters hung around the door, kicking it, waiting to see what would happen. All this time, the two oldest males stayed close to Kuif and were extremely friendly to her. After about an hour, we let Nikkie onto the island. The two males left Kuif and positioned themselves between her and the approaching Nikkie, their arms draped around each other’s shoulders. This was a sight to behold, given that they had been archenemies for years. Here they were, standing united against the young leader, perhaps fearing the same thing we feared. Nikkie, who had all his hair up, approached in a most intimidating manner but broke down when he saw that the other two were in no mood to budge. Kuif’s defense team must have looked incredibly determined, staring down the boss like that, because Nikkie fled. I couldn’t see their faces, but apes read as much in each other’s eyes as we do. Nikkie later approached Kuif under the watchful eyes of the other two males. He was nothing but gentle. His intentions will forever remain a mystery, but we sighed an enormous sigh of relief and I hugged the caretaker with whom I had run Kuif’s training. Chimps live under a cloud of potential violence, and infanticide is a leading cause of death both at zoos and in the wild. But in the end, when debating how aggressive we are as a species, chimpanzee behavior is only one piece of the puzzle. The behavior of our immediate ancestors would be more relevant. Unfortunately, there exist enormous holes in our knowledge of them, especially if we try to look back further than ten thousand years. There is no firm evidence that we have always been as violent as in the past few millennia. From an evolutionary standpoint, a few thousand years is nothing. For millions of years before, our ancestors may have led an easygoing existence in small groups of hunter-gatherers who had little to fight over, given how thinly populated the world was then. This would by no means have kept them from conquering the globe. It’s often thought that survival of the fittest means wiping out the unfit. But one can also win the evolutionary race by having a superior immune system or by being better at finding food. Direct combat is rarely the way one species replaces another. Thus, instead of annihilating the Neanderthals, we may simply have been more resistant to the cold or have been better hunters. It’s entirely possible that successful hominids “absorbed” less successful ones through crossbreeding, and therefore whether or not Neanderthal genes survive in you and me is an open question. If people joke that someone looks like a Neanderthal, they should think twice. In a Moscow laboratory I once saw a remarkable reconstruction of a Neanderthal face based on a skull. The scientists confided that they had never dared publicize the bust due to its uncanny resemblance to one of their country’s leading politicians, who might not have appreciated the comparison. THE APE IN THE CLOSET Would scratching a bonobo expose a hypocrite? We can be pretty sure that the notorious synopsis of veneer theory concerned people only. No one would suggest that animals are pulling the wool over each other’s eyes. This is why apes are crucial to the debate about the human condition. If they turn out to be better than brutes—even if only occasionally— the notion of niceness as a human invention begins to wobble. And if true pillars of morality, such as sympathy and intentional altruism, can be found in other animals, we will be forced to reject veneer theory altogether. Darwin was aware of these implications when he observed that “many animals certainly sympathize with each other’s distress or danger.” Of course they do. It’s not unusual for apes to care for an injured companion, slowing down if another lags behind, cleaning another’s wounds, or carrying fruit down from a tree to an elder who has lost her climbing abilities. One field report tells of an adult male chimp who adopted an orphan, carrying the sickly infant during travel, shielding it from danger, saving its life even though the two were presumed unrelated. In the 1920s, the American ape expert Robert Yerkes was so struck by the concern shown by one young chimp, Prince Chim, for his terminally ill companion, Panzee, that he admitted, “If I were to tell of his altruistic and obviously sympathetic behavior towards Panzee I should be suspected of idealizing an ape.” Yerkes’s admiration for Prince Chim’s sensitivity is telling, given that he probably knew more ape personalities than anyone else in the history of primatology. He paid tribute to this kind little anthropoid in a book titled Almost Human, in which he expressed doubt that Prince Chim was a regular chimp. A postmortem inspection has since revealed that he was indeed no chimp, but a bonobo. Yerkes did not know this—the bonobo wasn’t recognized as a species until years later. The first study to compare the behavior of bonobos and chimpanzees was carried out in the 1930s at the Hellabrunn Zoo. Eduard Tratz and Heinz Heck published their findings in 1954. Three bonobos had been terrified by the city’s bombardment one night during the war and had died of heart failure. The fact that all of the zoo’s bonobos died of fright but that none of the zoo’s chimps suffered the same fate attests to the bonobo’s sensitivity. Tratz and Heck made a long list of the differences between bonobos and chimps, which included references to the bonobo’s relative peacefulness, sexual behavior, and sensuality. Aggression is certainly not absent in the bonobo, but the treatment to which chimps occasionally subject one another, including biting and full-force hitting, is rare in bonobos. The hair of a male chimp stands on end at the slightest provocation. He will pick up a branch and challenge anyone perceived as weaker. Chimps are very much into status. By bonobo standards, the chimpanzee is a wild and untamed beast, or as Tratz and Heck put it, “The bonobo is an extraordinarily sensitive, gentle creature, far removed from the demoniacal Urkraft [primitive force] of the adult chimpanzee.” If this was known in 1954, one might ask, Why was the bonobo absent from the debates on human aggression, and why is it still not more widely known? Well, that study was published in German, and the time when English-speaking scientists read anything other than English is long past. Also, this study included only a few young apes in captivity, a tiny scientific sampling, so it may not have sounded too convincing. Bonobo field research, which got underway relatively late, still lags decades behind studies on the other great apes. Another reason is cultural: the bonobo’s eroticism was a topic few authors wanted to touch. This remains the case today. In the 1990s, a British camera crew traveled to the remote jungles of Africa to film bonobos only to stop their cameras each time an “embarrassing” scene appeared in the viewfinder. When a Japanese scientist assisting the crew asked why they weren’t documenting any sex, he was told “our viewers wouldn’t be interested.” But far more important than all of this is the fact that bonobos fail to fit established notions about human nature. Believe me, if studies had found that they massacre one another, everyone would know about bonobos. Their peacefulness is the real problem. I sometimes try to imagine what would have happened if we’d known the bonobo first and the chimpanzee only later or not at all. The discussion about human evolution might not revolve as much around violence, warfare, and male dominance, but rather around sexuality, empathy, caring, and cooperation. What a different intellectual landscape we would occupy! It’s only with the appearance of another of our cousins that the stranglehold of the killer ape theory began to loosen. Bonobos act as if they have never heard of the idea. Among bonobos, there’s no deadly warfare, little hunting, no male dominance, and enormous amounts of sex. If the chimpanzee is our demonic face, the bonobo must be our angelic one. Bonobos make love, not war. They’re the hippies of the primate world. Science had more trouble with them than a 1960s family had with its long-haired, pot-smoking black sheep who wanted to move back home. They turned off the lights, hid under the table, and hoped that the uninvited guest would go away. The bonobo is clearly an ape for our time. Attitudes have changed dramatically since Margaret Thatcher postulated her strident individualism. “There is no such thing as society,” she proclaimed. “There are individual men and women, and there are families.” Thatcher’s comment may have been inspired by the evolutionary views of her day, or perhaps it was the other way around. Either way, twenty years later, when huge corporate scandals have delivered the final pinprick to an inflated stock balloon, pure individualism does not sound so hot anymore. In the post-Enron era the public has begun to realize again—as if it had not always known—that unmitigated capitalism rarely brings out the best in people. Reagan and Thatcher’s “gospel of greed” went sour. Even Federal Reserve Chairman Alan Greenspan, a prophet of capitalism, hinted that it might be good to put the brakes on, explaining to a U.S. Senate committee in 2002, “It is not that humans have become any more greedy than in generations past. It is that the avenues to express greed have grown so enormously.” Anyone following evolutionary biology must have noticed a parallel change of heart. Suddenly books appeared with titles like Unto Others, Evolutionary Origins of Morality, The Tending Instinct, The Cooperative Gene, and my own Good Natured. There was less talk of aggression and competition and more of connectedness, of how societies hang together, of the origins of caring and commitment. What was stressed was the enlightened self-interest of the individual within a larger whole. Whenever interests overlap, competition will be constrained by the greater good. Along with other economic gurus of the era, Klaus Schwab declared that it was time for business “governed not only by rules but by values” while evolutionary biologists began to insist that “the rational pursuit of self-interest is sometimes an inferior strategy.” Perhaps both developments derived from broader swings in public attitude. Having rebuilt economies destroyed by war and having reached a level of prosperity unimaginable not too long ago, the industrialized world may finally be ready to focus on the social domain. We need to decide whether we are like Robinson Crusoes sitting on separate little islands, as Thatcher seemed to imagine, or members of complexly interwoven societies in which we care about each other and from which we derive our reason for being. Being more in agreement with the second possibility than the first, Darwin felt that people are born to become moral and that animal behavior supports this idea. He relates how a dog he knew would never walk by a basket where a sick friend lay, a cat, without giving her a few licks with his tongue. This, Darwin said, was a sure sign of the dog’s kind feelings. Darwin also tells the story of a zoo keeper with a wound at the nape of his neck. It was inflicted by a fierce baboon while the keeper was cleaning his cage. The baboon lived with a little South American monkey. Scared to death of his companion, the monkey was a warm friend to the keeper and in fact saved his life by distracting the baboon with bites and screams during his assault. The small monkey thus risked his own life, showing that friendship translates into altruism. Darwin felt it was the same for people. This was before we knew of the bonobo and before the latest findings of neuroscience. By placing people in brain scanners and asking them to resolve moral dilemmas, experts have discovered that such dilemmas activate ancient emotional centers deeply embedded in the brain. Instead of being a surface phenomenon in our expanded neocortex, moral decision-making apparently taps into millions of years of social evolution. Perhaps this sounds obvious, but it’s monumentally at odds with the view of morality as a cultural or religious veneer. I’ve often wondered how a position so plainly wrong could have been advocated for so many years. Why were altruists seen as hypocrites, why were emotions left out of the debate, and why did a book boldly titled The Moral Animal deny that morality comes naturally to us? The answer is that evolutionary authors were making the “Beethoven error.” By this, I mean the assumption that process and product need to resemble each other. Listening to Ludwig van Beethoven’s perfectly structured music, one would never guess what his poorly heated apartment looked like. Visitors complained that the composer lived in the dirtiest, smelliest, most disorderly place imaginable, strewn with wasting food, unemptied chamber pots, and filthy clothing, his two pianos buried under dust and papers. The maestro himself looked so slovenly that he was once arrested as a vagrant. No one asks how Beethoven could have created his intricate sonatas and noble piano concertos in such a pigsty. We all know that wonderful things can originate under atrocious circumstances, that process and product are separate things, which is why the enjoyment of a good restaurant is rarely enhanced by a visit to its kitchen. Yet confusion between the two has led some to believe that since natural selection is a cruel, pitiless process of elimination it must produce cruel and pitiless creatures. A nasty process must produce nasty behavior, or so the thinking went. But nature’s pressure cooker has created both fish that lunge at anything that moves (including their own offspring) and pilot whales, which are so attached to each other that they beach themselves together if one of them gets disoriented. Natural selection favors organisms that survive and reproduce, pure and simple. How they accomplish this is left open. Any organism that can do better by becoming either more or less aggressive than the rest, more or less cooperative, or more or less caring will spread its genes. The process does not specify the road to success any more than the inside of a Viennese apartment tells us what kind of music will be floating out its window. ANALYZING APES Every late afternoon at the Arnhem Zoo, the keepers and I would call Kuif out of the colony for the daily bottle-feeding of Roosje. Before she would come in carrying her adopted child, however, there always was a strange ritual. We’re used to apes greeting each other, which they do after long absences, by either kissing and embracing (chimps) or some sexual frottage (bonobos). Kuif was the first ape I have ever seen do good-bye (we call it “saying goodbye,” but obviously an ape can only “do good-bye”). Before she would enter the building, Kuif would approach Mama, the respected alpha female of the group and her best friend, to give her a kiss. After this, she would seek out Yeroen, the oldest male, to do the same. Even if Yeroen was asleep at the far end of the island, or deep into a grooming session with one of his buddies, Kuif would make a grand detour to catch him. It reminded me of how we’re not to leave a party without saying farewell to the hosts. For greeting, all that’s needed is delight at the sight of a familiar individual. Many social animals display this response. Saying good-bye is more complex, as it requires a glance into the future: the realization that you will not see someone for a while. I noticed another such glance one day when a female chimp collected all the straw from her night cage, deliberately scooping up every last bit until her arms were overflowing, and carried it all outside to the island. No chimp ever walks around with straw, so this caught our attention. It was November, and the days were getting cold. Apparently, this female had decided she was going to stay warm outside. At the moment she gathered the straw she could not feel the cold—she was in a heated building—so she must have extrapolated from the previous day to the next. She spent the whole day in her straw nest, which she couldn’t leave since everyone else was waiting to steal from it. This is the sort of intelligence that draws many of us to the study of apes. Not just their aggressive or sexual behavior, much of which they share with other animals, but the surprising amount of insight and finesse they put into everything they do. Since much of this intelligence is hard to pinpoint, studies on captive apes are absolutely essential. In the same way that no one would try to measure a child’s intelligence by watching him or her run around in the school yard, the study of ape cognition demands a hands-on approach. One needs to be able to present the apes with problems to see how they solve them. Another advantage of captive apes under enlightened conditions (meaning spacious outdoor areas and a naturalistic group size) is that one can watch their behavior much more closely than is possible in the field, where at critical moments they tend to disappear in the undergrowth. My favorite office (I have several) has a large window overlooking the chimps at the Yerkes Field Station, allowing me to see everything that goes on. They can’t hide from me (nor I from them, as is clear each time I try to eat my lunch unnoticed). Simple observation is the reason that power politics, reconciliations after fights, and tool-use were first discovered in captive apes and were confirmed only later in the wild. Typically, we conduct observations with binoculars and a keyboard attached to a computer into which we type every social event we witness. We have a long list of codes for play, sex, aggression, grooming, nursing, and myriad subtle distinctions within each category, and we enter data on a continuous basis in the format of “who does what to whom.” If events become too complicated, such as when a massive fight breaks out, we film it or, like a sportscaster, we narrate the events into a tape recorder. This way, we gather literally hundreds of thousands of observations, then program a computer to sort through the data. Despite the pleasure we take in our work, primate research has its tedious side. When we want to present the apes with a problem, we call them out of their group into a small building. Since we cannot force them to participate, we depend on their willingness. Not only do all the apes know their names, they also know each other’s names, so that one can ask individual A to fetch B. The trick is, of course, to make the experiment a pleasant experience. Computers with joysticks really attract them. My assistant only needs to show the cart with equipment and the volunteers will be lining up. As with children, the immediate feedback of a computer gives apes a thrill. In one experiment, Lisa Parr presented Yerkes chimpanzees with hundreds of pictures that I had taken at the Arnhem Zoo. With an ocean between these chimps, we could be sure they had never seen those faces before. One face would appear on the computer screen and then two more faces, one of which matched the first. The chimpanzee would be given a sip of juice for moving the cursor to the matching face. Face recognition had been tested before, but apes were not particularly good at it. Previous experiments, however, had used human faces on the assumption that these are easy to tell apart. Not for chimpanzees. They were far better with the faces of other chimps. Lisa showed that they see similarities not only between different pictures of the same face, but also between pictures of mother and offspring. In the same way that if I went through your family album, I could probably tell your relatives from your in-laws, chimps recognize the marks of kinship. They seem just as sensitive to their faces as we are to ours. Another study asked if chimps can deliberately point things out to others. The earlier story of Kanzi and Tamuli suggests they can, but the claim remains controversial. Some scientists focus on pointing with the hand or index finger, which is the way we point. However, I see no reason to take such a limited view. Nikkie once communicated with me using a much more subtle technique. He had gotten used to my throwing wild berries across the moat. One day while I was taking data I had totally forgotten about the berries, which hung on a row of tall bushes behind me. Nikkie had not. He sat down right in front of me, locked his red-brown eyes on mine, and—once he had my attention—abruptly jerked his head and eyes away from mine to fixate on a point over my left shoulder. He then looked back at me and repeated the move. I may be dense compared to an ape, but the second time I followed his gaze, spotting the berries. Nikkie had indicated what he wanted without a single sound or hand gesture. There is obviously no point to such “pointing” unless you understand that another hasn’t seen what you have seen, which means realizing that not everyone has the same information. A telling experiment on ape pointing was conducted by Charles Menzel at the same Language Research Center that is home to Kanzi. Charlie let a female chimpanzee named Panzee watch while he hid food in a forested area near Panzee’s cage. Panzee followed the food-hiding from behind the bars. Since she could not go where Charlie was, she would need human help to get the food. Charlie would dig a small hole in the ground and hide a bag of M&M’s or place a candy bar in some bushes. Sometimes he would do this after all people had left for the day. This meant that Panzee could not communicate with anybody about what she knew until the next day. When caretakers arrived in the morning, they didn’t know about the experiment. Panzee first had to get their attention and then provide information to someone who did not know what she knew and who at first had no clue what she was “talking” about. During a live demonstration of Panzee’s skills, Charlie noted as an aside to me that caretakers generally have a higher opinion of apes’ mental abilities than the philosophers and psychologists who write on the topic, few of whom have interacted with these animals on a daily basis. It was essential for the experiment, he explained, that Panzee dealt with people who took her seriously. All those recruited by Panzee said they were at first surprised by her behavior, but soon they understood what she was trying to get them to do. Following her pointing, beckoning, panting, and calling, they had no trouble finding the item hidden in the forest. Without her instructions, they would not have known where to look. Panzee never pointed in the wrong direction or to any location used on earlier occasions. The result was communication about a past event, present in the ape’s memory, to people who knew nothing about it and were unable to give her any clues. I offer these examples to make the point that there is excellent research on apes to rely upon when making statements about their sense of the past, sense of the future, face recognition, and social behavior in general. Even though in this book I favor lively examples, trying to put a face on what we know about our nearest relations, there exists an entire body of academic literature to back up most of my claims. Not all of them, mind you, which explains why disagreements persist and why there is no end in sight for my line of work. A conference on the great apes might attract one or two hundred experts, but this is nothing compared to the typical meeting of psychologists or sociologists, which easily counts ten thousand. As a result, we are nowhere near the level of understanding of apes that many of us would like to be. Most of my colleagues are field-workers. Whatever the advantages of research on captive apes, it can never replace the study of natural behavior. For every remarkable ability demonstrated in the laboratory, we want to know what it means for wild chimps and bonobos, what kind of benefits they gain from it. This relates to the evolutionary question, Why did the ability arise in the first place? For face recognition the benefits are pretty obvious, but what about a sense of the future? Field-workers have discovered that traveling chimpanzees sometimes gather grass stems and small twigs hours before arriving at a site where they will be fishing for ants or termites. The tools they need are picked up on the way at a place where they are abundant. It’s entirely possible that apes plan their travel routes with this in mind. What’s perhaps most significant about this research is not what apes reveal about our instinctual side. With their slow development (they reach adulthood at around sixteen) and ample learning opportunities, apes are really not that much more instinctual than we are. Apes make lots of decisions in their lives, such as whether to threaten a newborn or defend it or whether to save a bird or abuse it. What we compare, therefore, are the ways in which humans and apes handle problems through a combination of natural tendencies, intelligence, and experience. It’s impossible to extract from this mixture what is inborn and what is not. Nevertheless, the comparison is instructive if only because it makes us step back and look into a mirror that shows a different side of ourselves than we are used to. You place your hand in a bonobo’s and notice that your thumb is longer, you grab a bonobo’s upper arm and have never felt muscles that hard, you pull at its lower lip and feel how much more lip it has than you, you look into its eyes and get a look back that is exactly as inquisitive as yours. All of this is revealing. My goal is to make the same comparisons with regard to social life and to show that there is not a single tendency that we do not share with these hairy characters we love to make fun of. If people laugh at primates at the zoo, they do so, I suspect, precisely because they’re unsettled by the mirror held up to them. Otherwise, why do strange-looking animals such as giraffes and kangaroos not cause similar hilarity? Primates arouse a certain nervousness because they show us ourselves in a brutally honest light, reminding us, in Desmond Morris’s felicitous phrase, that we are mere “naked apes.” It’s this honest light that we seek, or ought to seek, and the beauty is that now that we know more about the bonobo, we can see ourselves reflected in two complementary mirrors. SIX THE BIPOLAR APE On Striking a Balance Are we best characterized by hate or by love? What is most critical for survival: competition or cooperation? Are we more like chimpanzees or bonobos? Such questions are a waste of time for the bipolar characters that we are. It’s like asking if a surface is best measured by its length or by its width. Even worse are attempts to consider only one pole at the expense of the other. Nevertheless, this is what the West has been doing for centuries by depicting our competitive side as somehow more authentic than our social one. But if people are as selfish as is assumed, how do they form societies? The traditional view is that of a contract among our ancestors, who decided to live together “by covenant only, which is artificial,” as Thomas Hobbes put it. We are seen as loners who reluctantly joined forces: smart enough to pool resources, but lacking any true attraction to our own kind. The old Roman proverb “Homo homini lupus” (“man is wolf to man”) captures this asocial vision that continues to inspire law, economics, and political science today. The problem isn’t just that this saying misrepresents us, but it also insults one of the most gregarious and loyal cooperators in the animal kingdom —so loyal, in fact, that our ancestors wisely domesticated them. Wolves survive by bringing down prey larger than themselves—such as caribou or moose— which they do through teamwork. Upon return from the hunt, they regurgitate meat for nursing mothers, the young, and sometimes the sick and old who stayed behind. Like chanting soccer fans, they reinforce pack unity by howling together before and after the hunt. There’s no lack of competition, but wolves can’t afford to let it run its course. Loyalty and trust come first. Behavior that undermines the bedrock of cooperation is dampened to prevent a meltdown of the social harmony upon which survival depends. A wolf who would let narrow individual interests prevail would soon find himself alone chasing mice. Apes know the same solidarity. In a study in Taï National Park in Ivory Coast, chimpanzees took care of group mates wounded by leopards, licking away their blood, carefully removing dirt, and preventing flies from coming near the wounds. They waved the flies away, protected injured companions, and traveled slowly if these couldn’t keep up. All of this makes perfect sense given that chimpanzees live in groups for a reason, the same way wolves and people are group-animals for a reason. We would not be where we are today had our ancestors been socially aloof. What I see, therefore, is the opposite of the traditional image of a nature “red in tooth and claw,” in which the individual comes first and society is a mere afterthought. One can’t reap the benefits of group life without contributing to it. Every social animal strikes its own balance between the two. Some are relatively nasty, others relatively nice. But even the harshest societies, such as those of baboons and macaques, limit internal strife. People often imagine that in nature weakness automatically means elimination—a principle hyped as the “law of the jungle”—but in reality social animals enjoy considerable tolerance and support. Otherwise, what would be the point of living together? I used to work with a group of rhesus macaques that showed great acceptance of Azalea, a mentally retarded juvenile born in their midst. Since Azalea possessed a triplet of chromosomes, her condition resembled that of human Down’s syndrome. Rhesus monkeys normally punish anyone who violates the rules of their strict society but Azalea was able to get away with the gravest blunders, such as threatening the alpha male. It was as if everyone realized that nothing they did would ever change her ineptness. Similarly, a freeranging macaque group in the Japanese Alps included a congenitally handicapped female named Mozu, who could barely walk, and certainly not climb, as she lacked both hands and feet. A frequent star of Japanese nature documentaries, Mozu was fully accepted by her group to the point that she lived a long life and raised five offspring. So much for survival of the fittest. There is plenty of that, too, of course, but there’s no need to caricature the life of our relatives as one led while constantly looking over their shoulders. Primates find great comfort in each other’s company. Getting along with others is a critical skill because survival chances outside the group—where there are predators and hostile neighbors—are dismal. Primates who find themselves alone meet a quick death. This explains why they spend an extraordinary amount of time—up to 10 percent of the day—servicing social ties by grooming others. Field studies have shown that female monkeys with the best social connections have the most surviving offspring. AUTIST MEETS GORILLA Bonding is so fundamental that an American woman with Asperger’s syndrome, a form of autism, who had failed to come to terms with her condition while living among people, found inner peace after she began taking care of zoo gorillas. Or perhaps it was the gorillas who took care of her. Dawn Prince- Hughes describes how people would unnerve her with their direct stares and direct questions to which they wanted immediate answers. The gorillas, on the other hand, left her space, avoided eye contact, and conveyed a comforting calm. Most of all, they were patient. Gorillas are “oblique” characters in that they rarely engage in face-to-face contact. Moreover, like all the apes, they lack the white sclera around the iris that makes the human gaze such an unsettling signal. Our eye coloring enhances communication, yet it also prevents subtleties of communication available to apes with their completely dark eyes. Moreover, apes rarely stare the way we do: they glance. They have incredible peripheral vision and follow much around them from the corners of their eyes. It’s something to get used to. How often have I thought that apes failed to pay attention, only to be proven wrong? They hadn’t missed a thing. The way the gorillas empathized with Prince-Hughes by “looking without looking, and understanding without speaking,” as she called it, took place via postures and body mimicry—the ancient animal language of connection. The colony’s mighty silverback, Congo, was the most sensitive and comforting, directly responding to signs of distress. This comes as no surprise given that the male gorilla, despite his ferocious King Kong reputation, is a born protector. The horrifying tales of gorilla attacks with which colonial hunters used to come home were designed to impress us with human rather than gorilla bravery. But in fact, a charging gorilla male is prepared to die for his family. That it takes an autistic person—someone considered deficient in interpersonal skills—to pick up on the primacy of ape bonding, and the deep kinship we sense with hairy bodies similar to ours, is remarkable. That PrinceHughes was pulled out of her solitude by gorillas rather than by chimpanzees or bonobos makes sense in view of gorilla temperament. These apes are not nearly as extroverted as chimps and bonobos. Take the following ordeal that a Swiss zoo went through. One night, its chimps managed to remove the skylight of their indoor housing and escape to the roof, after which some of them traveled through the city, jumping from house to house. It took days to retrieve the apes, and the zoo was lucky that none of them were shot by the police or electrocuted by a power line. This event gave a local animal rights group the idea of “liberating” the same zoo’s gorillas. Without giving much thought to what might be best for the animals, they climbed onto the ape house at night and removed a skylight above the gorilla quarters. But even though the apes had many hours to escape, they didn’t. The next morning, the caretakers found all of them sitting where they usually sat, staring with amazement up into the air, fascinated by the gaping hole above them. None of them had had the curiosity to climb out, and the skylight was simply put back into place. This, in a nutshell, is the temperamental difference between chimps and gorillas. Our lineage’s state of nature is one of bonding and support to the degree that even someone with autism perceives it. Or perhaps precisely such a person, since our obsession with the spoken word stands in the way of a full appreciation of nonverbal cues, such as postures, gestures, expressions, and tone of voice. Without body cues our communication loses its emotional content and becomes mere technical information. We could just as easily use flashing cards with “I love you” or “I am angry.” It is well known that people whose faces lose their expressiveness because of some neurological disorder and who therefore cannot echo the emotions of others (such as by a smile or a frown), plunge into abject loneliness. Our species finds life barely worth living without the body language that cements us together. Origin stories that neglect this deep connection by presenting humans as loners who grudgingly came together are ignorant of primate evolution. We belong to a category of animals known among zoologists as “obligatorily gregarious,” meaning that we have no option but to stick together. This is why fear of ostracism lurks in the corners of every human mind: being expelled is the worst thing that can befall us. It was so in biblical times, and it remains so today. Evolution has instilled a need to belong and to feel accepted. We are social to our core. TAMED CONTRADICTIONS A twenty-year-old Dodge Dart that I once owned taught me that the most critical part of a car is not its engine. The car would stop completely only if I applied my full weight to the brake pedal. On a quiet morning with little traffic, I drove it slowly to a nearby garage. Even though I arrived safely, the trip was frightening and I dreamed for months afterward of driving a car that would slow but not stop. Nature’s checks and balances are as essential as a car’s brakes. Everything is regulated, all is kept in control. Mammals and birds, for example, have made the evolutionary leap toward warm-bloodedness, yet run into trouble each time they overheat. In hot weather or after exercise, they cool off by sweating, flapping their ears, or panting heavily with their tongues hanging out. Nature had to put a brake on body temperature. Similarly, every songbird has its optimum egg size, optimum clutch size, optimum travel distance for foraging, optimum prey size, and so on. Birds that deviate from the norm by laying too many eggs or looking for insects too far from the nest lose out in the evolutionary race. This also applies to conflicting social tendencies, such as competition and cooperation, selfishness and sociability, strife and harmony. Everything is balanced around an optimum. Being selfish is inevitable and necessary, but only up to a point. This is what I meant when I called human nature a Janus head: we are the product of opposing forces, such as the need to think of our own interests and the need to get along. If I emphasize the latter, it’s because of the traditional emphasis on the former. Both are closely interconnected and contribute to survival. The very capacities that promote peace, such as reconciliation after a fight, would never have evolved in the absence of conflict. In a bipolar world, every capacity hints at its very opposite. We have discussed specific paradoxes, such as the link between democracy and hierarchy, between the nuclear family and infanticide, and between fairness and competition. In each case, it takes several steps to get from the one to the other, but wherever we turn, social institutions result from an interplay between opposing forces. Evolution is a dialectical process. Human nature, too, is inherently multidimensional, and the same applies to chimpanzee and bonobo nature. Even if the chimp’s nature is more violent and the bonobo’s more peaceful, chimps do resolve conflicts and bonobos do compete. In fact, chimpanzee peacemaking is all the more impressive given their obvious violent streak. Both apes have both tendencies, but each reaches a different balance. Being both more systematically brutal than chimps and more empathic than bonobos, we are by far the most bipolar ape. Our societies are never completely peaceful, never completely competitive, never ruled by sheer selfishness, and never perfectly moral. Pure states are not nature’s way. What’s true for human society is also true for human nature. One can find both kindness and cruelty, nobility and vulgarity—sometimes all in the same person. We’re full of contradictions, but mostly tamed ones. Talk of “tamed contradictions” may sound obscure, even mystical, but they’re all around us. The solar system is a perfect example. It results from two opposing forces, one directed inward, the other outward. The sun’s gravity balances the planets’ centrifugal motions so perfectly that the entire solar system has stayed together for billions of years. On top of the inherent duality of human nature comes the role of intelligence. Even if we customarily overestimate our rationality, there is no denying that human behavior is a combination of drive and intelligence. We exert little control over ancient urges for power, sex, safety, and food, but we habitually weigh the pros and cons of our actions before we engage in them. Human behavior is seriously modified by experience. This may sound too obvious to even mention, but it is a radically different way of putting things than the way biologists used to talk. In the 1960s, almost every noticeable tendency of the human species was labeled an “instinct,” and Konrad Lorenz’s Instinktlehre (German for “instinct doctrine”) even included a “parliament” of instincts to tie them all together. The problem with the term “instinct,” however, is that it downplays the role of learning and experience. A similar trend exists in some contemporary circles, this time favoring the term “module.” The human brain is compared to a Swiss Army knife to which evolution has one by one added modules for everything from face-recognition and tool-use to child care and friendship. Unfortunately, no one knows exactly what a brain module is, and the evidence for their existence is no more tangible than the evidence for instincts. It is undeniable that we have inborn predispositions, yet I don’t see us as blind actors carrying out nature’s genetic programs. I see us rather as improvisers who flexibly adjust to other improvisers on the scene with our genes offering hints and suggestions. The same applies to our fellow primates. Let me explain this with the example of Yeroen—at the Arnhem Zoo—who had injured his hand in a fight. Yeroen was building a coalition with the up-and-coming Nikkie, but in the shuffles leading to their partnership, Nikkie had bitten him. Although it wasn’t a deep wound, Yeroen limped heavily. After a couple of days, however, we got the impression that he limped mainly when Nikkie was around. I found this hard to believe, so we set out to conduct systematic observations. Each time we saw Yeroen walk with a limp, we recorded Nikkie’s whereabouts. This revealed that Nikkie’s field of vision mattered a great deal. Yeroen would walk past the sitting Nikkie, for example, from a point in front of him to a point behind him and the whole time he was in Nikkie’s view he would hobble pitifully, but once he had passed Nikkie, he would walk perfectly normally again. Yeroen seemed to be faking a limp so that his partner would go easy on him and perhaps show him some sympathy. Hurting one’s buddy is never a smart move, and Yeroen seemed to be pointing this out to Nikkie by exaggerating the pain he was in. Putting on a façade is of course familiar to us, since we do it all the time. A couple tries to look happy in public to hide a strained marriage, or people laugh at an unfunny joke told by their boss. Keeping up appearances is something we share with the apes. Recently, we looked at hundreds of records of wrestling matches among young chimpanzees to see when they laugh the most. Playing apes open their mouth in an expression that looks like the human laugh. We were particularly interested in youngsters far apart in age, as it’s not unusual for their games to get too rough. As soon as this happens, the mother of the younger partner steps in, sometimes hitting its playmate over the head. Obviously, the older chimp wants to avoid this. We found that juveniles playing with infants laughed a great deal whenever the infant’s mother was watching. It was as if they were saying “Look how much fun we’re having!” They laughed far less if they found themselves alone with the infant. Their behavior thus depended on whether mom could see them. Under her eyes, they projected a jolly mood so as to be left alone. Pretense during play or among political rivals is one reason I have trouble with the theory of animals as blind actors. Instead of being genetically programmed when to limp or when to laugh, apes are acutely aware of their social environment. Like humans, they ponder many options in front of them and decide what to do dependent on the circumstances. In the laboratory, apes are usually tested on abstract problems, such as finding rewards pointed out by experimenters or seeing the difference among four, five, or six items (a capacity known as “numerosity”). If they fail, as they sometimes do, the conclusion is often that we’re smarter than they are. In the social domain, however, in which apes deal with those they’ve known all their lives, they give the impression of being about as intelligent as we are. One crude way to test this would be to place a human in a chimp colony. This is obviously unrealistic as a chimp’s strength far outstrips a man’s, but imagine that we could find someone strong enough to stand up to adult chimps. We might be able to see how well he or she would fare within an ape community. The challenge for the human would be to win over friends without being too submissive, because without some level of assertiveness, one will just end up at the bottom of the pecking order or worse. Success will require that, just as in real life, the person be neither a bully nor a doormat. There would be no point trying to hide fear or hostility, because human body language is an open book to chimps. My prediction is that an ape colony would prove no easier to master than an average collection of people at work or at school. All of this is to say that ape social life is full of intelligent decision-making. For this reason, comparisons among humans, chimps, and bonobos go well beyond shared “instincts” or “modules,” however defined. All three species face similar social dilemmas and need to overcome similar contradictions while going after status, mates, and resources. They apply their full brainpower to find solutions. True, our species looks farther ahead and weighs more options than the apes do, but this hardly seems a fundamental difference. Even if we wield the better chess computer, we’re still all playing chess. FOREVER YOUNG Many people believe that our species is still evolving to ever greater heights, while the apes have simply stood still. But did our fellow primates really stop evolving? And is our species really still on the move? Ironically, the opposite may be true. Perhaps our evolution has stopped, whereas evolutionary pressures still operate on the apes. Evolution works through the survival of variants that outreproduce other variants. A couple of centuries ago this still applied to our species. In unhealthy places, such as rapidly growing urban areas, the death rate of people outstripped their birthrate. This meant that some had larger families than others, and yet others no families at all. Nowadays, in contrast, the number of children reaching the age of twenty-five is close to 98 percent. Under such circumstances, everyone has a shot at being represented in the gene pool. Good nutrition and modern medicine have removed the selection pressures driving human evolution. For example, women and babies used to run serious risks during labor. A narrow birth canal (relative to our outsized skull) was partly to blame, meaning that there was continuous evolutionary pressure to keep the canal wide. Cesarean sections changed all that. In the United States, 26 percent of births are by C-section, and in some private clinics in Brazil the rate is as high as 90 percent. More and more women with narrow birth canals will survive, passing on a trait that a few generations ago was a death warrant. The inevitable result will be a growing number of C-sections until natural birth becomes the exception. Continued evolution requires a danse macabre around those who died before they reproduced. This may still happen in the industrialized world—for example, in the form of a devastating flu pandemic. Those with superior immunity will survive to pass on their genes, such as happened during the Black Death of the fourteenth century, which in a span of five years killed an estimated 25 million people in Europe alone. Some scientists believe that a highly infectious Ebolalike virus was transmitted from person to person. Immunity to such viruses is presently more common in Europe than in other parts of the world, possibly owing to this massive moment of natural selection. Similarly, we can expect growing resistance to the human immunodeficiency virus (HIV) in sub-Saharan Africa, where nearly 10 percent of the population is infected. It is known that a small minority of people resist infection and that another minority fails to develop AIDS even if infected. Biologists label such people “adaptive mutations.” They will propagate until their descendants cover the continent. The process will be completed only after enormous loss of life, however. Wild chimpanzees in Africa must already have gone through this: they carry the closely related simian immunodeficiency virus (SIV) without any ill effects. Apart from immunity, which will likely keep adjusting, it is unclear which genetic changes we can still expect in our species. Humanity may have reached its biological peak, so to speak, one we will not be able to surpass unless we set up deliberate breeding programs (which I hope we’ll never do). Despite funny books such as The Darwin Awards, which describe people who remove themselves from the gene pool by engaging in incomprehensibly stupid acts (such as the shoplifter who ran off while stuffing a pair of live lobsters with good-sized claws into his pants, thus causing an unplanned vasectomy), a few such accidents won’t improve the human race. So long as there’s no connection between intelligence and the number of children people bear, human brain size will remain what it is today. But what about culture? When cultural change was still slow, human biology kept up. Some cultural and genetic traits were transmitted together, a phenomenon known as “dual inheritance.” Our ancestors became lactose resistant, for example, when they started raising cattle. Every young mammal is able to digest milk, but the necessary enzyme typically turns off after weaning. In humans, this occurs after the age of four. Those who can’t handle lactose suffer diarrhea and vomiting whenever they drink fresh cow’s milk. This is the original condition of our species, and it’s typical of most adults in the world. Only the descendants of cattle herders, such as Northern Europeans and dairydependent African pastoralists, are able to absorb vitamin D and calcium from milk, a genetic change going back ten thousand years to when sheep and cattle were first domesticated. Today’s cultural developments, however, are too fast for biology to keep pace. Text-messaging via cell phones is unlikely to make our thumbs grow longer. Rather, we developed text-messaging for the thumbs our species already possesses. We have become experts at changing the environment to our advantage. Therefore, I don’t believe in the continued evolution of the human race—certainly not as it would affect body shape and behavior. We have removed the only handle biology has to modify us, which is differential reproduction. It is unclear if ape evolution will keep going even though apes are still subject to real pressures. The problem is that they are under too much pressure, giving them hardly any chance: they hover on the brink of extinction. For years, I have clung to the idea that given the large remaining stretches of rain forest in the world, there would always be apes to accompany us. But I have become pessimistic. Because of massive habitat destruction, large fires, illegal poaching, the bush meat trade (people in Africa actually eat apes), and most recently the Ebola virus sweeping through ape populations, there may be only two hundred thousand chimpanzees left in the wild, one hundred thousand gorillas, twenty thousand bonobos, and an equal number of orangutans. If this sounds like a lot of apes, compare this with the enemy—humans—which number more than six billion. It is an unequal battle, and the prediction is that by the year 2040 virtually every suitable ape habitat will be gone. We humans will be diminished if we cannot even protect the animals closest to us, who share almost all of our genes, and who differ from us only by degree. If we let them go, we can just as well let everything go and turn the idea that we are the only intelligent life on earth into a self-fulfilling prophecy. Even though I have studied apes in captivity all my life, I’ve seen enough of them in nature to feel that their life there—their dignity, their belonging, their role—is irreplaceable. To lose this would be to lose a big chunk of ourselves. Wild populations of apes are priceless when it comes to illuminating past evolution. We barely know, for example, why bonobos and chimpanzees differ so much from each other. What happened two million years ago when their branches split? Was the original ape more like a chimp or more like a bonobo? We know that bonobos presently live in a richer habitat than chimps, one that allows mixed groups of males and females to forage together. This permits greater social cohesion than in chimps, who in their quest for food split up into small parties. The “sisterhood” among unrelated females that is typical of bonobo society would not have been possible without predictable, abundant food sources. Bonobos have access to enormous fruit trees that allow many individuals to feed together, and they also consume herbs that are plentiful on the forest floor. Since the same herbs are also a staple of the gorilla’s diet, it has been speculated that the total absence of gorillas in the habitat of bonobos has left the bonobos a niche that remained closed to chimps, who compete with gorillas throughout their range. Bonobos have another interesting feature that connects them to us, which is that they are a “forever young” primate. This is known as the “neoteny” argument—applied to our own species ever since a Dutch anatomist made the shocking claim in 1926 that Homo sapiens looks like a primate fetus that has reached sexual maturity. Stephen Jay Gould considered retention of juvenile traits the hallmark of human evolution. He didn’t know about bonobos, the adults of which retain the small, rounded skull of a young chimp as well as the white tail tufts that chimps lose after the age of five. The voices of adult bonobos are as high-pitched as those of infant chimps, they stay playful all their lives, and even the females’ frontally oriented vulva is considered neotenous, a trait also present in our own species. Human neoteny is reflected in our naked skin and especially in our ballooning cranium and flat face. Human adults look like very young apes. Is the crown of creation arrested in its development? There is no doubt that our success as a species is tied to the fact that we have carried the inventiveness and curiosity of young mammals forward into adulthood. We have been named Homo ludens: the playful ape. We play games until we die, we dance and sing, and we add to our knowledge by reading nonfiction or taking senior university classes. There’s a great need for us to stay young at heart. Given that humanity cannot pin its hopes on continued biological evolution, it needs to build upon its existing primate heritage. Being only loosely programmed and having sipped from evolution’s youth potion, this heritage is rich and varied and full of flexibility. A WHIFF OF IDEOLOGY Owing to their near perfect coordination and willingness to sacrifice themselves for the whole, ant colonies are often compared to socialist societies. Both are a workers’ paradise. Yet next to the order of an anthill, even the best drilled human workforce looks like inefficient anarchy. People go home after work, drink, gossip, get lazy—none of which any self-respecting ant would ever do. Notwithstanding the massive indoctrination efforts by Communist regimes, people refuse to submerge themselves for the greater good. We are sensitive to collective interests, but not to the point of giving up our individual ones. Communism went under due to an economic incentive structure that was out of touch with human nature. Unfortunately, it did so only after causing immense suffering and death. Nazi Germany was quite a different ideological disaster. Here, too, the collective (das Volk) was placed above the individual, but instead of relying on social engineering, the methods of choice were scapegoating and genetic manipulation. People were divided into “superior” and “inferior” types, the first of which needed to be protected against contamination by the second. In the horrible medical language of the Nazis, a healthy Volk required removal of cancerous elements. This idea was followed to its extreme in a manner that has given biology a nasty reputation in Western societies. Don’t think that the underlying selectionist ideology was restricted to this particular time and place, however. In the early part of the twentieth century, the eugenics movement—which sought to improve humanity by “breeding from the fitter stocks”—enjoyed widespread appeal in both the United States and Great Britain. Based on ideas going back to Plato’s Republic, castration of criminals was considered acceptable. And Social Darwinism—the idea that in a laissezfaire economy the strong will out-compete the weak, resulting in general improvement of the population—still inspires political agendas today. In this view, the poor should not be aided so as not to upset the natural order. Political ideology and biology are awkward bedfellows, and most biologists prefer to sleep in a separate room. The reason we have been unsuccessful at this is the incredible appeal of the words “nature” and “natural.” They sound so reassuring that every ideology wants to embrace them. This means that biologists who write about behavior and society risk being sucked into the political spin zone. This happened, for example, after publication of our study on simian fairness. Having demonstrated that a monkey will refuse cucumber as soon as its neighbor gets grapes, newspapers used our findings to call for a more egalitarian society. “If monkeys hate unfair treatment, why shouldn’t we?” the op-ed pieces asked. This triggered strange reactions, such as one e-mail accusing us of being Communists. The writer felt that we were trying to undermine capitalism, which apparently doesn’t care for fairness. What the critic had failed to notice, though, was that the reactions of our monkeys paralleled the workings of the free market. What could be more capitalist than comparing what you get with what someone else is getting and complaining if the price isn’t right? In 1879, American economist Francis Walker tried to explain why members of his profession were in such “bad odor amongst real people.” He blamed it on their inability to understand why human behavior fails to comply with economic theory. We do not always act the way economists think we should, mainly because we’re both less selfish and less rational than economists think we are. Economists are being indoctrinated into a cardboard version of human nature, which they hold true to such a degree that their own behavior has begun to resemble it. Psychological tests have shown that economics majors are more egoistic than the average college student. Exposure in class after class to the capitalist self-interest model apparently kills off whatever prosocial tendencies these students have to begin with. They give up trusting others, and conversely others give up trusting them. Hence the bad odor. Social mammals, in contrast, know trust, loyalty, and solidarity. Like the chimps in Taï National Park, they don’t leave the unfortunate behind. Moreover, they have ways of handling potential profiteers, such as withholding cooperation from those who fail to cooperate themselves. Reciprocity allows them to build the sort of support system that many economists see as a chimera. In the group life of our close relatives, it’s not hard to recognize both the competitive spirit of capitalism and a well-developed community spirit. The political system that seems to fit us best would therefore have to balance the two. Not being ants, pure socialism doesn’t suit us. Recent history has shown what happens when individual ambition is stifled. But even though the fall of the Berlin Wall was hailed as a triumph of the free market, there is no guarantee that pure capitalism will fare any better than socialism did. Not that this form of government exists anywhere. Even the United States has an abundance of checks, balances, unions, and subsidies that constrain its marketplace. Compared to the rest of the world, though, the United States is an experiment in unbridled competition. This experiment has made it the richest nation in the history of civilization. Something puzzling is going on, however, as the nation’s health is increasingly lagging behind its wealth. The United States used to have the world’s healthiest and tallest citizens, but now ranks at the bottom among industrialized nations in terms of longevity and height and at the top in terms of teenage pregnancy and infant mortality. Whereas most nations have been adding nearly one inch per decade to their average height, the United States has not done so since the 1970s. The result is that Northern Europeans now tower on average three inches over Americans. This isn’t explained by recent United States immigrants, which constitute too tiny a fraction of the population to affect these statistics. In terms of life expectancy, too, the United States is not keeping up with the rest of the world. On this critical health index, Americans don’t even rank among the top twentyfive nations anymore. How to explain this? The first culprit that comes to mind is the privatization of health care, resulting in millions of uninsured people. But the problem may go deeper. British economist Richard Wilkinson, who has gathered global data on the connection between socioeconomic status and health, blames inequality. With its giant underclass, the income gap in the United States resembles that of many third-world nations. The top 1 percent of Americans has more income to spend than the bottom 40 percent taken together. This is a huge gap compared with Europe and Japan. Wilkinson argues that large income disparities erode the social fabric. They induce resentment and undermine trust, which causes stress to both the rich and the poor. No one feels at ease within such a system. The result is that the world’s richest nation now has one of its poorest health records. Whatever one thinks of a political system, if it fails to promote its citizens’ physical well-being, it has a problem. And so in the same way that Communism collapsed due to a mismatch between ideology and human behavior, unmitigated capitalism may be unsustainable as it celebrates the material well-being of a few while shortchanging the rest. It denies the basic solidarity that makes life bearable. In doing so, it goes against a long evolutionary history of egalitarianism, which in turn relates to our cooperative nature. Primate experiments show how cooperation breaks down if benefits aren’t shared among all participants, and human behavior likely follows the same principle. The book of nature thus offers pages that will please both liberals and conservatives, both those who believe that we are all in the same boat and those who put faith in the pursuit of self-interest. When Margaret Thatcher dismissed society as a mere illusion, she was clearly not describing the intensely social primates that we are. And when Petr Kropotkin, a nineteenth-century Russian prince, felt that the struggle for life could lead only to more and more cooperation, he was closing his eyes to free competition and its stimulating effects. The challenge is to find the right balance between the two. Our societies probably work best if they mimic as closely as possible the small-scale communities of our ancestors. We certainly did not evolve to live in cities with millions of people where we bump into strangers everywhere we go, are threatened by them in dark streets, sit next to them in the bus, and give them the finger in traffic jams. Like bonobos in their cohesive communities, our ancestors were surrounded by people they knew and dealt with every day. It’s remarkable that our societies are as orderly, productive, and relatively secure as they are. But city planners can and must do a better job at approximating the community life of old, in which everyone knew every child’s name and home address. The term “social capital” refers to the public safety and sense of security derived from a predictable environment and dense social network. Older neighborhoods in cities like Chicago, New York, London, and Paris do produce such social capital, but only because they were designed for people to live, work, do their shopping, and go to school in. This way people get to know each other and begin to share values. A young woman walking home in the evening will be surrounded by so many residents with a stake in safe streets that she can feel protected. She is surrounded by an unspoken neighborhood watch. The modern trend to physically separate places where human needs are satisfied disrupts this tradition, making us live at one place, shop at another, and work at yet another. It’s a disaster for community building, not to mention the time, stress, and fuel it takes to move all those people around. In the words of Edward Wilson, biology holds us “on a leash” and will let us stray only so far from who we are. We can design our life any way we want, but whether we will thrive depends on how well the life fits human predispositions. I encountered a vivid example of this while having afternoon tea with a young couple during a visit to an Israeli kibbutz in the 1990s. They had both been raised on nearby kibbutzim when children were still being separated from their parents to grow up with other children in the cooperative. The couple explained that this practice had now been abandoned and that parents were permitted to keep their children at home after school and at night. The change was a relief, they said, because having your children close “just feels right.” How obvious! The kibbutz had felt the leash’s limit. I hesitate to predict what we humans can and cannot do, but the mother-child bond would seem sacrosanct as it goes to the core of mammalian biology. We face the same sorts of limits when deciding what kind of society to build and how to achieve global human rights. We are stuck with a human psychology shaped by millions of years of life in small communities so that we somehow need to structure the world around us in a way recognizable to this psychology. If we could manage to see people on other continents as part of us, drawing them into our circle of reciprocity and empathy, we would be building upon, rather than going against, our nature. In 2004, the Israeli justice minister caused a political uproar by sympathizing with the enemy. Yosef Lapid questioned the plans of the Israeli army to demolish thousands of Palestinian homes in a zone along the Egyptian border. He had been touched by images on the evening news. “When I saw a picture on the TV of an old woman on all fours in the ruins of her home looking under some floor tiles for her medicines, I did think, ‘What would I say if it were my grandmother?’” Lapid’s grandmother was a Holocaust victim. The nation’s hardliners did not like to hear these sentiments, of course, and went out of their way to distance themselves from them. The incident goes to show how a simple emotion can widen the definition of one’s group. Lapid had suddenly realized that Palestinians were part of his circle of concern, too. Empathy is the one weapon in the human repertoire able to rid us of the curse of xenophobia. Empathy is fragile, though. In our close relatives it is switched on by events within their community, such as a youngster in distress, but it is just as easily switched off with regard to outsiders or members of other species, such as prey. The way a chimpanzee bashes in the skull of a live monkey to get at its brain by hitting it against a tree trunk is no advertisement for ape empathy. Bonobos are less brutal, but in their case as well empathy needs to pass several filters before it will be expressed. Often, the filters stop it, because no ape can afford to feel pity for all living things all the time. This applies equally to humans. Our evolutionary design makes it hard to identify with outsiders. We’ve been designed to hate our enemies, to ignore the needs of people we barely know, and to distrust anybody who doesn’t look like us. Even if within our communities we are largely cooperative, we become almost a different animal in our treatment of strangers. Such attitudes were summarized by Winston Churchill, long before he earned his reputation as a brave warrior-politician, when he wrote, “The story of the human race is War. Except for brief and precarious interludes, there has never been peace in the world; and before history began, murderous strife was universal and unending.” As we have seen, this is a gross exaggeration. No one denies our warrior potential, but Churchill definitely got the interludes wrong. Contemporary hunter-gatherer groups coexist in peace most of the time. This probably applied even more to our ancestors, who lived on a planet with lots of space and relatively little need for competition. They must have experienced long stretches of harmony between groups, interrupted only by brief interludes of confrontation. Even though circumstances have changed—making the maintenance of peace much harder than in those days—a return to the mind-set that enabled mutually beneficial intergroup relations is perhaps less of a stretch than it may seem to those stressing our warrior side. After all, we have at least as long a history of getting along with other groups as of fighting them. We have both the chimpanzee side in us, which precludes friendly relations between groups, and the bonobo side, which permits sexual mingling and grooming across the border. WHICH INNER APE? When Helena Bonham Carter was asked during an interview how she had prepared for her role of Ari in Planet of the Apes, she said that she had simply gotten in touch with her inner ape. She and the other actors went to a so-called simian academy to acquire ape postures and movements, but even though the petite Bonham Carter played a chimp, what she’d found within herself instead was, I believe, a sensual bonobo. The contrast between those two apes reminds me of a distinction by psychologists between HE and HA personalities. HE stands for “Hierarchy- Enhancing,” meaning a personality who believes in law and order and harsh measures to keep everybody in place. HA, on the other hand, stands for “Hierarchy-Attenuating,” meaning a personality who seeks to level the playing field. The point is not which tendency is more desirable, because it’s only together that they create human society as we know it. Our societies balance both types, having institutions that are either more HE, such as the criminal justice system, or more HA, such as civil rights movements and organizations that care for the poor. Each person leans toward one type or the other, and we might even classify entire species this way, with chimps being more HE and bonobos more HA. Do we perhaps act like a hybrid between those two apes? We know little about the behavior of actual hybrids, but they are biologically possible and do in fact exist. No self-respecting zoo would intentionally crossbreed two endangered primates, but there’s one report of a small French traveling circus featuring apes with curious voices. These apes were thought to be chimps, but to the expert ear their calls are as shrill as those of bonobos. It turns out that, unbeknownst to it, the circus long ago acquired a bonobo male, who became known as Congo. The trainer soon noticed this male’s insatiable sex drive, which he exploited by rewarding Congo’s best performances by a romp with the circus’ female apes, all chimpanzees. The resulting progeny—perhaps to be called “bonanzees” or “chimpobos”—walk upright with remarkable ease and strike everyone by their gentility and sensitivity. Perhaps we share a lot with these hybrids. We have the fortune of having not one but two inner apes, which together allow us to construct an image of ourselves that is considerably more complex than what we have heard coming out of biology for the past twenty-five years. The view of us as purely selfish and mean, with an illusory morality, is up for revision. If we are essentially apes, as I would argue, or at least descended from apes, as every biologist would argue, we are born with a gamut of tendencies from the basest to the noblest. Far from being a figment of the imagination, our morality is a product of the same selection process that shaped our competitive and aggressive side. That such a creature could have been produced through the elimination of unsuccessful genotypes is what lends the Darwinian view its power. If we avoid confusing this process with its products—the Beethoven error—we see one of the most internally conflicted animals ever to walk the earth. It is capable of unbelievable destruction of both its environment and its own kind, yet at the same time it possesses wells of empathy and love deeper than ever seen before. Since this animal has gained dominance over all others, it’s all the more important that it takes an honest look in the mirror, so that it knows both the archenemy it faces and the ally that stands ready to help it build a better world.