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The old male faced a choice worthy of a politician. Every day Yeroen was being groomed by two rivaling males, each one eager to gain his backing. He seemed to enjoy the attention. Being groomed by the mighty alpha male, the one who had deposed him a year earlier, was utterly relaxing because no one would dare disturb them. But being groomed by the second, younger male was tricky. Their get-togethers greatly upset alpha, who regarded them as plots against himself and tried to disrupt them. Alpha would put up all his hair and hoot and display around, banging doors and hitting females, until the other two males became so nervous that they’d break up and leave the scene. Separating them was the only way to calm down alpha. Since male chimps never cease to jockey for position and are always making and breaking pacts, innocent grooming sessions don’t really exist. Every single one carries political implications.

The current alpha male enjoyed massive popularity and support, including that of the old matriarch, Mama, leader of the females. If Yeroen had wanted an easy life, he would have opted to play sidekick to this male. He wouldn’t have rocked the boat, and there would never have been any threat to his position. Aligning himself with the ambitious young male, on the other hand, was fraught with risk. However big and muscular this male might be, he had barely left his adolescence behind. He was an untried entity who carried so little authority that whenever he tried to break up a female fight, as top males are wont to do, he risked the wrath of both contestants. Ironically, this meant that he did resolve the discord, but at his own expense. Instead of screaming at one another, the females now supported one another in chasing the would-be arbitrator. Once they got him cornered, however, they were smart enough not to physically grapple with him, being all too familiar with his speed, strength, and canine teeth. He had become a player to be reckoned with.

The alpha male, in contrast, was so skilled at peacekeeping, so impartial in his interventions, and so protective of the underdog that he had become immensely beloved. He had brought peace and harmony to the group after a long period of upheaval. Females were always ready to groom him and let him play with their children. They were likely to resist anyone who dared challenge his reign.

Nonetheless, this is exactly what Yeroen went for when he sided with the young upstart. The two of them entered a long campaign to dethrone the established leader that took a great toll in tensions and injuries. Whenever the young male would position himself at some distance from the alpha male, provoking him with increasingly loud hooting, Yeroen would go sit right behind the challenger, wrap his arms around his middle, and softly hoot along. This way there was no doubt about his allegiance. Mama and her female friends did resist this revolt, occasionally resulting in massive pursuits of both troublemakers, but the combination of the young male’s brawn and Yeroen’s brain was too much. From the start, it was obvious that Yeroen was not out to claim the alpha position for himself but was content to let his partner do the dirty work. They never backed down, and after several months of daily confrontations, the young male became the new alpha.

The two of them ruled for years, with Yeroen acting like a Dick Cheney or a Ted Kennedy, a power behind the throne; he remained so influential that as soon as his support began to waver, the throne wobbled. This happened occasionally after conflicts over sexually attractive females. The new alpha quickly learned that in order to keep Yeroen on his side, he’d need to grant him privileges. Most of the time Yeroen was allowed to mate with females, something the young alpha did not tolerate from any other male.

Why did Yeroen throw his support behind this parvenu instead of joining the established power? It is informative to look at studies of human coalition formation, in which players win games through cooperation, and to study the balance-of-power theories about international pacts. The basic principle here is the “strength is weakness” paradox, according to which the most powerful player is often the least attractive political ally because this player doesn’t really need others, hence takes them for granted and treats them like dirt. In Yeroen’s case, the established alpha male was too mighty for his own good. By joining him, Yeroen would have gained little, because all this male truly needed was his neutrality. The smarter strategy was to pick a partner who couldn’t win without him. By throwing his weight behind the young male, Yeroen became the kingmaker. He regained both prestige and fresh mating opportunities.

Machiavellian Intelligence

When I began observing the world’s largest chimpanzee colony, at Burgers’ Zoo in 1975, I had no idea that I’d be working with this species for the rest of my life. Just so, as I sat on a wooden stool watching primates on a forested island for an estimated ten thousand hours, I had no idea that I’d never again enjoy that luxury. Nor did I realize that I would develop an interest in power relations. In those days, university students were firmly antiestablishment, and I had the shoulder-long hair to prove it. We considered ambition ridiculous and power evil. My observations of the chimps, however, made me question the idea that hierarchies were merely cultural institutions, a product of socialization, something we could wipe out at any moment. They seemed more ingrained. I had no trouble detecting the same tendencies in even the most hippielike organizations. They were generally run by young men who mocked authority and preached egalitarianism yet had no qualms about ordering everyone else around and stealing their comrades’ girlfriends. It wasn’t the chimps who were odd, but the humans who seemed dishonest. Political leaders have a habit of concealing their power motives behind nobler desires such as a readiness to serve the nation and improve the economy. When the English political philosopher Thomas Hobbes postulated the existence of an insuppressible power drive, he was right on target for both humans and apes.

The biological literature proved to be of no help understanding the social maneuvering that I observed, so I turned to Niccol? Machiavelli. During quiet moments of observation, I read from a book that had been published more than four centuries earlier. The Prince put me in the right frame of mind to interpret what I was seeing on the chimpanzees’ forested island, though I’m pretty sure the Florentine philosopher never envisioned this particular application.

Among chimpanzees, hierarchy permeates everything. Whenever we set out to bring two females inside the building—as we often do for testing—one will be ready to get going on the task at hand while the other will hang back. The second female will barely take rewards and won’t touch the puzzle box, computer, or whatever else we’re using. She may be just as eager as the other, but she defers to her “superior.” There is no tension or hostility between them, and out in the group they may be the best of friends. One female simply dominates the other.

Among the males, in contrast, power is always up for grabs. It is not conferred on the basis of age or any other trait but has to be fought for and jealously guarded against contenders. Soon after my long stint as chronicler of their social affairs, I put pencil to paper to produce Chimpanzee Politics, a popular account of the power struggles that I had witnessed.1 I was risking my nascent academic career by ascribing intelligent social maneuvering to animals, an implication I had been trained to avoid at all cost. That doing well in a group full of rivals, friends, and relatives requires considerable social skill is something we now take for granted, but in those days animal social behavior was rarely thought of as intelligent. Observers would recount a rank reversal between two baboons, for example, in passive terms, as if it happened to them rather than was brought about by them. They would make no mention of one baboon following the other around, provoking one confrontation after another, flashing his huge canine teeth, and recruiting help from nearby males. It is not that the observers did not notice, but animals were not supposed to have goals and strategies, so the reports remained silent.

Deliberately breaking with this tradition, describing chimps as schmoozing and scheming Machiavellians, my book drew wide attention and enjoyed many translations. The U.S. Speaker of the House, Newt Gingrich, even put it on the recommended reading list for freshmen congressmen. The account met with far less resistance than I had dreaded, including from fellow primatologists. Obviously, the time was ripe, in 1982, for a more cognitive approach to animal social behavior. Even though I learned about it only after my own book, Donald Griffin’s Animal Awareness had come out just a few years before.2

My work was part of a new Zeitgeist, and I had a handful of predecessors to lean on. There was Emil Menzel, whose work on chimpanzee cooperation and communication postulated goals and hinted at intelligent solutions, and Hans Kummer, who never ceased to wonder what drove his baboons to act the way they did. Kummer wanted to know, for example, how baboons plan their travel routes, and who decides where to go—those in front or those in the back? He broke down the behavior into recognizable mechanisms, and stressed how social relationships serve as long-term investments. More than anyone before him, Kummer combined classical ethology with questions about social cognition.3

I was also impressed by In The Shadow of Man by a young British primatologist.4 By the time I read it, I was familiar enough with chimpanzees to be unsurprised by the specifics of Jane Goodall’s description of life at Gombe Stream in Tanzania. But the tone of her account was truly refreshing. She did not necessarily spell out the cognition of her subjects, but it was impossible to read about Mike—a rising male who impressed his rivals by loudly banging empty kerosene cans together—or the love life and family relations of matriarch Flo, without recognizing a complex psychology. Goodall’s apes had personalities, emotions, and social agendas. She did not unduly humanize them, but she related what they did in unpretentious prose that would have been perfectly normal for a day at the office but was unorthodox with regard to animals. It was a huge improvement over the tendency at the time to drown behavioral descriptions in quotation marks and dense jargon in order to avoid mentalistic implications. Even animal names and genders were often avoided. (Every individual was an “it.”) Goodall’s apes, in contrast, were social agents with names and faces. Rather than being the slaves of their instincts, they acted as the architects of their own destinies. Her approach perfectly fit my own budding understanding of chimpanzee social life.

Yeroen’s allegiance to the young alpha was a case in point. Not that I could resolve how and why he had made his choice, in the same way that it was impossible for Goodall to know if Mike’s career might have been different in the absence of kerosene cans, but both stories implied deliberate tactics. Pinpointing the cognition behind such behavior requires collecting a mass of systematic data as well as performing experiments, such as the strategic computer games that we now know chimps are extraordinarily good at.5

Let me briefly offer two examples of how these issues may be tackled. The first concerns a study at the Burgers’ Zoo itself. Conflicts in the colony rarely remained restricted to the original two contestants, since chimps have a tendency to draw others into the fray. Sometimes ten or more chimps would be running around, threatening and chasing one another, uttering high-pitched screams that could be heard a mile away. Naturally, every contestant tried to get as many allies on his or her side as possible. When I analyzed hundreds of videotaped incidents (a new technique at the time!), I found that the chimpanzees who were losing the battle beseeched their friends by stretching out an open hand to them. They tried to recruit support in order to turn things around. When it came to the friends of their enemies, however, they went out of their way to appease them by putting an arm around them and kissing their face or shoulder. Instead of begging for assistance, they sought to neutralize them.6

To know the friends of your opponents takes experience. It implies that individual A is aware not only of her own relations with B and C but also of the relation between B and C. I dubbed this triadic awareness, since it reflects knowledge of the entire ABC triangle. It is the same with us, when we realize who is married to whom, who is a son of whom, or who is the employer of whom. Human society could not function without triadic awareness.7

The second example concerns wild chimpanzees. It is well known that there is no obvious connection between a male’s rank and his size—the biggest, meanest male does not automatically reach the top. A small male with the right friends also has a shot at the alpha position. This is why male chimps put so much effort into alliance formation. In an analysis of years of data collected at Gombe, a relatively small alpha male spent far more time grooming others than did larger males in the same position. Apparently, the more a male’s position depends on support from third parties, the more energy he needs to invest into diplomacy, such as grooming.8 In a study in the Mahale Mountains, not far from Gombe, Toshisada Nishida and his team of Japanese scientists observed an alpha male with an exceptionally long tenure of more than a decade. This male developed a “bribery” system, selectively sharing prized monkey meat with his loyal allies, while denying such favors to his rivals.9

Years after Chimpanzee Politics, these studies confirmed the tit-for-tat deal making that I had implied. But even while I was writing my book, supportive data were being gathered. Unknown to me, Nishida had followed an older male at Mahale, named Kalunde, who had moved himself into a key position by playing off younger, competitive males against one another. These young males sought Kalunde’s support, which he handed out rather erratically, making himself indispensable to the advancement of any one of them. Being the dethroned alpha male, Kalunde made a comeback of sorts, but like Yeroen, he didn’t claim the top position for himself. He rather acted as power behind the scenes. The situation was so eerily similar to the saga I had described that I was thrilled, two decades later, to meet Kalunde in person. Toshi, as the late Nishida was known to his friends, invited me for some fieldwork, which I gladly accepted. He was one of the world’s greatest chimpanzee experts, and it was a treat to follow him around through the jungle.

Living in the camp near Lake Tanganyika, one realizes that running water, electricity, toilets, and telephones are greatly overrated. It is entirely possible to survive without them. Every day the goal was to get up early, eat a quick breakfast, and get going before the sun rose. The chimps would have to be found, and the camp had several trackers to assist us. Fortunately, chimps are incredibly noisy, which makes them easy to locate. Chimps do not travel all in a single group but are spread out over separately traveling “parties” of just a few individuals each. In an environment with low visibility, they rely heavily on vocalizations to stay in touch. Following an adult male, for example, you continuously see him stop, cock his head, and listen to others in the distance. You see him decide how to respond, by replying with his own calls, silently moving toward the source (sometimes in such a hurry that you are left struggling through tangled vines), or continue on his merry way as if what he just heard lacked any relevance.

By then Kalunde was the oldest male, only about half the size of a prime adult male. Being around forty, he had shrunk. But despite his advanced age, he was still into political games, frequently accompanying and grooming the beta male until alpha returned from a long period of absence. Alpha had traveled to the fringes of the community territory, escorting a sexually receptive female. High-ranking males may go for weeks on end “on safari” with a female, as it is known, in order to avoid competition. I knew about alpha’s unexpected return only because Toshi told me in the evening, but I had noticed great agitation in the males that I had been following the whole day. They were restless, running up and down the hills, totally exhausting me. Alpha’s characteristic hooting and drumming on empty trees had announced his return, making everyone hypernervous. In the following days, it was fascinating to see Kalunde switching camps. One moment he would be grooming the returning alpha; the next he’d be hanging out with the beta male, as if trying to decide which side he should be on. He offered the perfect illustration of a tactic that Toshi had dubbed “allegiance fickleness.”10

You can imagine that we had much to talk about, especially comparing wild versus zoo chimps. Obviously, there are major differences, but it is not as simple as some people think, especially those who wonder why one would study captive animals at all. The goals of both types of research are quite different, and we need both. Fieldwork is essential to understanding the natural social life of any animal. For anyone who wants to know how and why their typical behavior evolved, there is no substitute for observing them in their natural habitat. I have visited many field sites, from capuchin monkeys in Costa Rica and woolly spider monkeys in Brazil to orangutans in Sumatra, baboons in Kenya, and Tibetan macaques in China. I find it very informative to see the ecology of wild primates and to hear from colleagues what sort of issues they are fascinated by. Fieldwork is nowadays very systematic and scientific. The days of a few scribbled observations in a notebook are gone. Data collection is continuous and systematic, typed into handheld digital devices, and complemented with fecal and urine samples that allow DNA analysis and hormone assays. All this hard, sweaty work has enormously advanced our understanding of wild animal societies.

Yet in order to get at behavioral details and the cognition behind them, we need more than fieldwork. No one would try to measure a child’s intelligence by watching him run around in the schoolyard with his friends. Mere observation doesn’t offer much of a peek into the child’s mind. Instead, we bring the child into a room and present him with a coloring task or a computer game, let her stack wooden blocks, ask questions, and so on. This is how we measure human cognition, and it is also the best way to determine how smart apes are. Fieldwork offers hints and suggestions but rarely allows firm conclusions. One may encounter wild chimpanzees who crack nuts with stones, for example, but it is impossible to know how they discovered this technique or how they learn it from one another. For this, we need carefully controlled experiments on naïve chimpanzees who receive nuts and stones for the first time.

Captive apes under enlightened conditions (such as a sizable group in a spacious outdoor area) have the added advantage of providing a close-up look at naturalistic behavior that one can’t get in the field. Here apes can be watched and videotaped much more fully than is possible in the forest, where primates often disappear into the undergrowth or canopy as soon as things get interesting. Fieldworkers are often left to reconstruct events based on fragmented observations. To do so is an art, and they are very good at it, but it falls short of the behavioral detail routinely collected in captivity. If one studies facial expressions, for example, zoomed-in high-definition videos that can be slowed down are essential, which require well-lit conditions rarely encountered in the field.

No wonder the study of social behavior and cognition has fostered integration between captive and fieldwork. The two represent different pieces of the same puzzle. Ideally, we use evidence from both sources to support cognitive theories. Observations in the field have often inspired experiments in the lab. Conversely, observations in captivity—such as the discovery that chimpanzees reconcile after fights—have stimulated observations in the field on the same phenomenon. If, on the other hand, experimental outcomes clash with what is known about a species’s behavior in the wild, it may be time to try a new approach.11

With regard to the question of animal culture, in particular, captive and fieldwork are now often combined. Naturalists document geographic variation in the behavior of a given species, suggesting a local origin and transmission. But they often cannot rule out alternative accounts (such as genetic variation between populations), which is why we need experiments to determine if habits can spread by one individual watching another. Is the species capable of imitation? If so, this greatly strengthens the case for cultural learning in the field. Nowadays we move back and forth all the time between both sources of evidence.

But all these interesting developments happened long after my observations at Burgers’ Zoo. Following Kummer’s example, my goal at the time was to spell out what social mechanisms may underlie observed behavior. Apart from triadic awareness, I spoke of divide-and-rule strategies, policing by dominant males, reciprocal deal making, deception, reconciliation after fights, consolation of distressed parties, and so on. I developed such a long list of proposals that I devoted the rest of my career to fleshing them out, at first through detailed observations, but later also experimentally. Proposals take so much less time to make than their verification! The latter can be very instructive, though. One can set up experiments, for example, in which one individual can do another one favors, as we did with our capuchin monkeys, but then add a condition in which the partner can do favors in return. This allows favors to travel in both directions between two parties. We found that monkeys become noticeably more generous if favors can be done mutually than if only one of them has the opportunity.12 I love this kind of manipulation, since it allows far more solid conclusions about reciprocity than any observational account. Observations never quite clinch the deal the way experiments can.13

Even though Chimpanzee Politics opened a new agenda for research while introducing Machiavelli’s thinking to primatology, I was never quite happy with “Machiavellian intelligence” as a popular label for this field.14 This term implies an end-justifies-the-means manipulation of others, ignoring a vast amount of social knowledge and understanding that has nothing to do with one-upmanship. When a female chimpanzee resolves a fight between two juveniles over a leafy branch by breaking it into two and handing each youngster a piece, or when an adult male chimpanzee helps an injured, limping mother by picking up her offspring to carry it for her, we are dealing with impressive social skills that don’t fit the “Machiavellian” label. This cynical identifier made sense a few decades ago, when all animal (including human) life was customarily depicted as competitive, nasty, and selfish, but over time my own interests have drifted into the opposite direction. I have devoted most of my research to the exploration of empathy and cooperation. The exploitation of others, by using them as “social tools,” remains a great topic and is an undeniable aspect of primate sociality, but it is too narrow a focus for the field of social cognition as a whole. Caring relationships, the maintenance of bonds, and attempts to keep the peace are equally worthy of attention.

The intelligence required to effectively deal with social networks may explain why the primate order underwent its remarkable brain expansion. Primates have exceptionally large brains. Dubbed the Social Brain Hypothesis by British zoologist Robin Dunbar, the connection with sociality is supported by a relation between a primate’s brain size and its typical group size. Primates that live in larger groups generally have larger brains. I always find it hard, though, to separate social and technical intelligence, since many big-brained species are strong in both domains. Even species that hardly handle any tools in the wild, such as rooks and bonobos, may be quite good at it in captivity. It remains true, though, that social challenges have been neglected for too long in discussions of cognitive evolution, which tend to focus on interactions with the environment. Given how all-important social problem solving is in the lives of our subjects, primatologists have been right to amend this view.15

Triadic Awareness

Siamangs—large black members of the gibbon family—swing high up in the tallest trees of the Asian jungle. Every morning, the male and female burst into spectacular duets. Their song begins with a few loud whoops, which gradually build into ever louder, more elaborate sequences. Amplified by balloonlike throat sacs, the sound carries far and wide. I have heard them in Indonesia, where the whole forest echoed with their sound. The siamangs listen to one another during breaks. Whereas most territorial animals need only to know where their boundaries run and how strong and healthy their neighbors are, siamangs face the added complexity that territories are jointly defended by pairs. This means that pair-bonds matter. Troubled pairs will be weak defenders, while bonded pairs will be strong ones. Since the song of a pair reflects their marriage, the more beautiful it is, the more their neighbors realize not to mess with them. A close-harmony duet communicates not only “stay out!” but also “we’re one!” If a pair duets poorly, on the other hand, uttering discordant vocalizations that interrupt one another, neighbors hear an opportunity to move in and exploit the pair’s troubled relationship.16

To understand how others relate to one another is a basic social skill that is even more important for group-living animals. They deal with a far greater variety than the siamang. In a baboon or macaque troop, for example, a female’s rank in the hierarchy is almost entirely decided by the family from which she hails. Owing to a tight network of friends and kin, no female escapes the rules of the matrilineal order according to which daughters born to high-ranking mothers will themselves become high-ranking, while daughters from families at the bottom will also end up at the bottom. As soon as one female attacks another, third parties move in to defend one or the other so as to reinforce the existing kinship system. The youngest members of the top families know this all too well. Born with a silver spoon in their mouth, they freely provoke fights with everyone around, knowing that even the biggest, meanest female of a lower clan will not be allowed to assert herself against them. The youngster’s screams will mobilize her powerful mother and sisters. In fact, it has been shown that screams sound different depending on the kind of opponent a monkey confronts. Thus, it is immediately clear to the entire troop whether a noisy fight fits or violates the established order.17

The social knowledge of wild monkeys has been tested by playing the distress calls of a juvenile from a loudspeaker hidden in the bushes at a moment when the juvenile itself is out of sight. Hearing this sound, nearby adults not only look in the direction of the speaker but also peek at the juvenile’s mother. They recognize the juvenile’s voice and seem to connect it with its mother, perhaps wondering what she is going to do about the trouble her offspring is in.18 The same sort of social knowledge can be seen at more spontaneous moments, when a juvenile female picks up an infant that is unsteadily walking about, only to carry it back to its mother, which means that she knows which female the infant belongs to.

In white-faced capuchin monkeys, the American anthropologist Susan Perry analyzed how individuals form coalitions during fights. Having followed these hyperactive monkeys for over two decades, Susan knows them all by name and life history. During a visit to her field site in Costa Rica, I saw the characteristic coalition stance firsthand. Known as the overlord, two monkeys threaten a third with stares and wide-open mouths, one leaning on top of the other. Their opponent thus faces an intimidating display of two monkeys wrapped into one, with both threatening heads stacked on top of each other. Comparing these coalitions with known social ties, Susan found that capuchins preferentially recruit friends who are dominant over their opponent. This by itself is rather logical, but she also found that instead of seeking the support of their best buddies, they specifically recruit those who are closer to themselves than to their opponent. They seem to realize that there is no point appealing to their opponent’s buddies. This tactic, too, requires triadic awareness.19

Two white-faced capuchin monkeys adopt an “overlord” position, so that their adversary is confronted by two threatening faces and sets of teeth at once.

Capuchins solicit support by abruptly jerking their heads back and forth between a potential supporter and their adversary, a behavior known as headflagging, which is also used against danger, such as a snake. In fact, these monkeys threaten everything they don’t like, a tendency sometimes used to manipulate attention. Susan once observed the following deceptive sequence:

Pursued by a coalition of three higher-ranking males, Guapo suddenly stopped in his tracks and began to produce frantic snake alarm calls while looking at the ground. I was standing by him and could plainly see that there was nothing there but bare ground. He headflagged to Curmudgeon [one of his enemies] for support against the imaginary snake. Guapo’s pursuers stopped short and stood up on their hind legs to see if there was a snake. After cautious inspection, they once again began threatening Guapo. Switching tactics he glanced up at a passing magpie jay (a nonmenacing bird) and did three bird alarms in rapid succession—calls that are usually reserved for large raptors and owls. Guapo’s opponents looked up, saw that it was not a dangerous bird, and again resumed threatening Guapo. He reverted to the snake alarm call tactic once again vehemently bouncing at the bare patch of ground, threatening the “snake” vocally. Although Curmudgeon continued to glare at Guapo for a bit longer, the rest of the group stopped threatening him, and he was able to resume foraging for insects, moving slowly and nonchalantly towards Curmudgeon while occasionally casting a furtive glance in his direction.20

While such observations suggest but cannot prove high intelligence, there is an urgent need for information on the cognition of wild primates. Fieldworkers are finding ingenious ways to collect it. In Budongo Forest, in Uganda, for example, Katie Slocombe and Klaus Zuberbühler set out to record the screams of chimpanzees under threat or attack. These loud vocalizations serve to recruit aid, which prompted the scientists to see if the acoustics of screams depend on the audience. Given the dispersed lives of wild chimpanzees, only individuals who are within earshot—the audience—are likely to provide aid to a screaming victim. In addition to finding that the intensity of the calls reflected the intensity of the attack, the scientists noted a subtle deception encoded in them. Chimpanzee victims apparently exaggerate their screams (making the attack sound more severe than it truly is), provided their audience includes individuals that outrank their attacker. In other words, whenever the big bosses are around, chimp victims scream bloody murder. Their vocal distortion of the truth suggests precise knowledge of their opponent’s status relative to everyone else.21

More evidence that primates know one another’s relationships comes from the way they classify others based on family membership. Some studies have explored their tendency to redirect aggression. Recipients of aggression often look for a scapegoat, not unlike the way people who get reprimanded at work may come home to maltreat their spouse and children. Given their strict hierarchies, macaques are a prime example. As soon as one of these monkeys gets threatened or chased, it will threaten or chase somebody else, always an easy target. Redirected hostility thus travels down the pecking order. Remarkably, redirecting monkeys prefer to target the family of the original aggressor. One monkey will be attacked by a high-ranking individual, then look around to spot a younger, less powerful member of her attacker’s family to take her tensions out on this poor soul. This way redirection resembles revenge, since it makes the family of the instigator pay.22

The same knowledge of family relations also serves more constructive purposes, such as when after a fight between two monkeys of different families, tensions are resolved by other members of the same families. Thus, if play between two juveniles turns into a screaming fight, their mothers may get together to make up for their children. It is an ingenious system, but again it requires every monkey to know to which family every other monkey belongs.23

Categorizing others into families may be a case of stimulus equivalence, as proposed by the late Ronald Schusterman, an American marine mammal specialist. Ron kept the strangest and most delightful animal laboratory that I have ever set a slippery foot in, since it consisted of not much more than an outdoor swimming pool in sunny Santa Cruz, California. It was the ultimate wet lab. To the side of the pool stood a few wooden panels on which symbols could be mounted for his sea lions. The animals swam in the pool, racing around faster than any human ever could, only to jump out for a few seconds and touch a symbol with their wet noses. Ron’s star performer was his favorite pinniped, named Rio. If Rio made the right choice, a fish would be thrown at her, and she’d dive right back into the pool. She did all this in one fluid movement, catching the fish while sliding back into the water, reflecting perfect coordination between experimenter and subject. Ron explained that most tests were too simple for Rio, resulting in her getting bored and losing her concentration. Making errors, she’d get mad at Ron for not giving her enough fish and angrily toss all her plastic toys out of the pool.

Rio had learned to associate arbitrary symbols. She’d first learn that symbol A belongs with B, then that B belongs with C, and so on. After rewarding her for making the right connections, Ron would surprise her with a brand-new combination, such as A and C. If A and B are equivalent as well as B and C, then A and C must be equivalent, too. Would Rio extrapolate from the previous associations, and group A, B, and C together? She did, applying this logic to combinations that she had never encountered before. Ron saw this as the prototype of how animals may mentally group individuals together, such as families or cliques.24 We do the same: if you learned to connect me first with one of my brothers, then also with another one (I have five!), you should also group those two brothers together in the same family even if you have never encountered them together. Equivalence learning makes for quick and efficient categorization.

Ron went further, speculating about other unseen connections. For example, chimpanzee males have been known to angrily attack and destroy the empty night nests that rival males have left behind in trees at the border of their territory. Unable to attack the enemy itself, the next best target is apparently a nest that they have built. It reminds me of a time in the Netherlands, when owners of black Suzuki Swifts had a tough time. They suffered frequent nasty remarks from people and worse, such as intentional damage to their cars. This situation arose after someone with murderous intentions had driven a black Suzuki Swift into a festive crowd on Queen’s Day, killing eight people. The car itself was obviously not at fault, but humans are quick to connect the dots. A hated action turned a specific car brand into a hated object. It all boiled down to stimulus equivalence.

Knowing as we do the spontaneous use of triadic awareness, the next question is how it is acquired. To find out, we need experiments. Is it enough for animals to just watch others? In one study, the French psychologist Dalila Bovet rewarded rhesus monkeys at Georgia State University for identifying the dominant monkey in a video. The observing monkeys didn’t know the individuals they were watching and had to judge their relationship purely on the basis of behavior. For example, one monkey in the video would chase another, after which the observer would be trained to select the dominant one (the one who had done the chasing) on a freeze frame of the scene. After learning to do this, the observing monkeys generalized to behaviors that didn’t look like chasing but also indicated dominance. Subordinate rhesus monkeys, for example, communicate their position to the dominant by baring their teeth in a wide grin. Bovet showed videos in which this signal was being exchanged. Even though these scenes were new to the observing monkeys, they correctly picked the dominant party. The conclusion was that they have a concept of rank and are quick to evaluate the status of unknown individuals on the basis of how they interact with others.25

Ravens may show a similar understanding, as evidenced by their reactions to vocalizations played over a loudspeaker. Ravens recognize one another’s voices and pay close attention to dominant and subordinate calls. But then the playbacks were manipulated to make it sound as if a dominant individual had turned submissive. Hearing evidence of a brewing overthrow, the ravens would stop what they were doing and listen while showing signs of distress. They were most upset by rank reversals among members of their own sex in their own group, but they reacted also to status reversals between ravens in an adjacent aviary. The investigators concluded that ravens have a concept of status that goes beyond their own position. They know how others typically interact and are alarmed by deviations from this pattern.26

In a related question, I have always wondered if captive chimpanzees evaluate status differences among the people around them. I once worked at a zoo with a demanding director who would occasionally visit the facilities and order everyone around, pointing out problems, saying this needed to be cleaned, and that needed to be moved, and so on. Showing typical alpha conduct, he kept everyone on their toes, as a good director should. Even though the chimps rarely interacted with him—he never fed them or talked to them—they picked up on this behavior. They treated this man with the utmost respect, greeting him with submissive grunts from a great distance (which they didn’t do for anyone else) as if they realized, Here comes the boss, the one everyone around here is nervous about.

It’s not just in relation to dominance that chimpanzees make such judgments. One of the best illustrations of their triadic awareness occurs in mediated conflict resolution. After a fight between male combatants, a third party may induce them to make peace. Interestingly, it’s only female chimps who do so, and only the highest-ranking ones among them. They step in when two male rivals fail to reconcile. The male rivals may be sitting near each other and avoiding eye contact, unable or unwilling to make the first move. If a third male were to approach, even to make peace, he’d be perceived as a party to the conflict. Male chimps form alliances all the time, so their presence is never neutral.

This is where the older females come in. The matriarch of the Arnhem colony, Mama, was the mediator par excellence: no male would ignore her or carelessly start a fight that might incur her wrath. She would approach one of the males and groom him for a while, then slowly walk toward his rival while being followed by the first. She would look around to check on the first and return to tug at his arm if he was reluctant. Then she’d sit down next to the second male, while both males would groom her, one on each side. Finally Mama would slip away from the scene, and the males would pant, splutter, and smack more loudly than before—sounds that signal grooming enthusiasm; but by then they would of course be grooming each other.

In other chimpanzee colonies, too, I have seen old females reduce male tensions. It is a risky affair (the males are obviously in a grumpy mood), which is why younger females, instead of trying to mediate themselves, encourage others to do so. They approach the top female while looking around at the males who are refusing to make up. This way, they try to get something going that they can’t accomplish safely by themselves. Such behavior demonstrates how much chimpanzees know about the social relationships of others, such as what has happened between the rival males, what has to be done to restore harmony, and who will be the best one to undertake this mission. It is the sort of knowledge that we take for granted in our own species, but without it animal social life could never have reached its known complexity.

Proof in the Pudding

While cleaning out the old library at the Yerkes Primate Center, we unearthed forgotten treasures. One was the old wooden desk of Robert Yerkes, which is now my personal desk. The other was a film that probably had not been looked at for half a century. It took us a while to find the right projector, but it was worth the trouble. Lacking sound, the film had written titles inserted in between poor-quality black-and-white scenes. It featured two young chimpanzees working together on a task. In true slapstick style, befitting the movie’s flickering format, one of the chimps would slap the other on her back every time her dedication flagged. I have shown a digitized version to many audiences, causing much laughter in recognition of the humanlike encouragements. People are quick to grasp the movie’s essence: apes have a solid understanding of the advantages of cooperation.

The experiment was run in the 1930s by Meredith Crawford, a student of Yerkes.27 We see two juveniles, Bula and Bimba, pulling at ropes attached to a heavy box outside their cage. Food has been placed on the box, which is too heavy for one of them to pull in alone. The synchronized pulling by Bula and Bimba is remarkable. They do so in four or five bursts, so well coordinated that you’d almost think they were counting—“one, two, three … pull!”—but of course they are not. In a second phase, Bula has been fed so much that her motivation has evaporated, and her performance is lackluster. Bimba solicits her every now and then, poking her or pushing her hand toward the rope. Once they have successfully brought the box within reach, Bula barely collects any food, leaving it all to Bimba. Why did Bula work so hard with so little interest in the payoff? The likely answer is reciprocity. These two chimps know each other and probably live together, so that every favor they do for each other will likely be repaid. They are buddies, and buddies help each other out.

This pioneering study contains all the ingredients later expanded upon by more rigorous research. The cooperative pulling paradigm, as it is known, has been applied to monkeys, hyenas, parrots, rooks, elephants, and so on. The pulling is less successful if the partners are prevented from seeing each other, so success rests on true coordination. It is not as if the two individuals pull at random and, by luck, happen to pull together.28 Furthermore, primates prefer partners who cooperate eagerly and are tolerant enough to share the prize.29 They also understand that a partner’s labor requires repayment. Capuchin monkeys, for example, seem to appreciate each other’s effort in that they share more food with a partner who has helped them obtain it than with one whose help went unneeded.30 Given all this evidence, one wonders why the social sciences in recent years have settled on the curious idea that human cooperation represents a “huge anomaly” in the natural realm.31

It has become commonplace to assert that only humans truly understand how cooperation works or know how to handle competition and freeloading. Animal cooperation is presented as mostly based on kinship, as if mammals were social insects. This idea was quickly disproven when fieldworkers analyzed DNA extracted from the feces of wild chimpanzees, which allowed them to determine genetic relatedness. They concluded that the vast majority of mutual aid in the forest occurs between unrelated apes.32 Captive studies have shown that even strangers—primates who didn’t know each other before they were put together—can be enticed to share food or exchange favors.33

Despite these findings, the human uniqueness meme keeps stubbornly replicating. Are its proponents oblivious to the rampant, varied, and massive cooperation found in nature? I just attended a conference on Collective Behavior: From Cells to Societies, which addressed the extraordinary ways in which single cells, organisms, and entire species realize goals together.34 Our best theories about the evolution of cooperation stem from the study of animal behavior. Summarizing these ideas in his 1975 book Sociobiology, E. O. Wilson helped launch the evolutionary approach to human behavior.35

Excitement about Wilson’s grand synthesis seems to have faded, though. Perhaps it was too sweeping and inclusive for disciplines that consider humans in isolation. Chimpanzees in particular are nowadays often depicted as so aggressive and competitive that they can’t be truly cooperative. If this applies to our closest relatives, so the thinking goes, we can justifiably ignore the rest of the animal kingdom. One prominent advocate of this position, the American psychologist Michael Tomasello, extensively compared children and apes, which has led him to conclude that our species is the only one capable of shared intentions in relation to common goals. He once condensed his view in the catchy statement “It is inconceivable that you would ever see two chimpanzees carrying a log together.”36

At Burgers’ Zoo, live trees are surrounded by electrified wire, yet the chimps manage to get into them anyway. They break long branches out of dead trees and carry them to a live one, where one of them holds the branch steady while another scales it.

This is quite an assertion, given Emil Menzel’s photographed and filmed sequences of juvenile apes recruiting one another to collectively prop a heavy pole up against the wall of their enclosure in order to get out.37 I have regularly seen chimps use long sticks as ladders to get across hot wire surrounding live beech trees; one chimp holds the stick while another scales it to reach fresh leaves without getting shocked. We have also videotaped two adolescent females who regularly tried to reach the window of my office, which overlooks the chimp compound at the Yerkes Field Station. Both females would exchange hand gestures while moving a heavy plastic drum right underneath my window. One ape would jump onto the drum, after which the other would climb on top of her and stand on her shoulders. The two females would then synchronously bob up and down like a giant spring; the one standing on top would reach for my window every time she came close. Well synchronized and clearly of the same mind, these females played this game often in alternating roles. Since they never succeeded, their common goal was largely imaginary.

Literally carrying a log together may not be part of these efforts, but this behavior is trained for all the time in Asian elephants. Until recently, the forest industry in Southeast Asia employed elephants as beasts of burden; now they are rarely used for this purpose anymore, but they still demonstrate their skills for tourists. At the Elephant Conservation Center near Chiang Mai, in Thailand, two tall adolescent bulls will effortlessly pick up a long log with their tusks, each standing on one end, draping their trunks over the log to keep it from rolling off. Then they will walk in perfect unison several meters apart, with the log between them, while the two mahouts on their necks sit chatting and laughing and looking around. They are most certainly not directing every move.

Training is obviously part of this picture, but one cannot train any animal to be so coordinated. One can train dolphins to jump synchronously because they do so in the wild, and one can teach horses to run together at the same pace because wild horses do the same. Trainers build on natural abilities. Obviously, if one elephant were to walk slightly faster than the other while carrying the log, or hold it at the wrong height, the whole enterprise would quickly unravel. The task requires step-by-step harmonization of rhythm and movement by the bulls themselves. They have moved from an “I” identity (I perform this task) to a “we” identity (we do this together), which is the hallmark of collective action. They end their performance by lowering the log together, moving it from their tusks into their trunks and then slowly to the ground. They set the heaviest log down on a pile without a single sound, impeccably coordinated.

When Josh Plotnik tested elephants on the cooperative pulling paradigm, he found a solid understanding for the need to synchronize.38 Teamwork is even more typical of group hunters, such as humpback whales, which blow hundreds of bubbles around a school of fish; the column of bubbles traps the fish like a net. The whales act together to make the column tighter and tighter, until several of them surface through its center with mouths wide open to swallow the bounty. Orcas go even further, in an action so astonishingly well coordinated that few species, including humans, would be able to match it. When orcas along the Antarctic Peninsula spot a seal on an ice floe, they reposition the floe. It takes lots of hard work, but they push it out into open water. Then four or five whales line up side by side, acting like one giant whale. They rapidly swim in perfect unison toward the floe, creating a huge wave that washes off the unlucky seal. We don’t know how the killer whales agree on the lineup or how they synchronize their actions, but they must be communicating about it before making their move. It is not entirely clear why they do it, because even though the orcas afterward carry the seal around, they often end up releasing it. One seal was deposited back onto a different ice floe to live another day.39

The highest level of joint intentionality in the animal kingdom is perhaps achieved by killer whales. After spy-hopping to get a good look at a seal on an ice floe, several of them will line up and swim toward the floe at high speed in perfect unison. Their behavior creates a massive wave that washes the seal off the floe straight into some waiting mouths.

On land, lions, wolves, wild dogs, Harris’s hawks (teams of which control the pigeons at London’s Trafalgar Square), capuchin monkeys, and so on, exhibit plenty of tight teamwork, too. The Swiss primatologist Christopher Boesch has described how chimpanzees hunt colobus monkeys in Ivory Coast: some males act as drivers, while others take up distant positions high up in a tree as ambushers waiting for the monkey troop to escape in their direction through the canopy. Since these hunts take place in the dense jungle of Taï National Park, and both the chimps and the monkeys are dispersed, it is hard to pinpoint what is going on in three-dimensional space, but it appears to involve role division and the anticipation of prey movement. The prey is captured by one of the ambushers, who potentially could quietly slink away with the meat but does exactly the opposite. During the hunt the chimps are silent, but as soon as a monkey is captured, they erupt in a pandemonium of hooting and screaming that draws everyone in, leading to a large cluster of males, females, and young jostling for position. I once stood under a tree (in a different forest) while this happened, and the deafening noise above me left little doubt about how highly chimps prize their meat. Sharing appears to favor hunters over latecomers—even the alpha male may go empty-handed if he failed to participate. The chimpanzees seem to recognize contributions to success. The communal feast that ensues is the only way to sustain this sort of cooperation, because why would anyone invest in a joint enterprise if not for the prospect of a joint payoff?40

These observations obviously contradict the view that chimpanzees, and other animals, lack joint action based on shared intentions. One can imagine the head butting between two scientists with such diametrically opposite views as Boesch and Tomasello, who have offices in the same building. Was their appointment as codirectors of the Max Planck Institute in Leipzig an experiment on how human collaboration fares in the face of disagreement? Given these divergent perspectives, let me return to the experiments that led Tomasello to his human uniqueness claim. After testing both children and apes on a cooperative pulling task, he concluded that only the children exhibit shared intentionality.

The question of comparability has come up before, however, and fortunately there are photographs of the respective setups.41 One shows two apes in separate cages, each with a little plastic table in front of him that he can pull closer with a rope. Oddly, the apes do not occupy a shared space, as in Crawford’s classical study. Their cages are not even adjacent: there is distance and two layers of mesh between them—a situation that hampers visibility and communication. Each ape focuses on its own end of the rope, seemingly unaware of what the other is up to. The photo of the children, in contrast, shows them sitting on the carpeting of a large room with no barriers between them. They, too, are using a pulling apparatus, but they sit side by side in full view of each other and are free to move around, touch each other, and talk. These different arrangements go a long way toward explaining why the children showed shared purpose, and the apes did not.

Had this comparison concerned two different species—rats and mice, say—we would never have accepted such dissimilar setups. If rats had been tested on a joint task while sitting side by side and mice while being kept apart, no sensible scientist would permit the conclusion that rats are smarter or more cooperative than mice. We’d demand the same procedure. Comparisons between children and apes get exceptional leeway, however, which is why studies keep perpetuating cognitive differences that, in my mind, are impossible to separate from methodological ones.

In view of the ongoing controversy, we decided to move away from pair-wise testing—whether separate or together—and develop a more naturalistic setup. I sometimes refer to it as our proof-in-the-pudding experiment, since we sought to determine once and for all how well chimps handle conflicting interests: what happens to cooperation in the face of competition? The only way to see which tendency prevails is to provide an opportunity for the chimpanzees to express both at the same time.

My student Malini Suchak came up with the right apparatus to test a colony of fifteen chimps at the Yerkes Field Station. Mounted on the fence of their outdoor enclosure was an apparatus that required very precise coordination to be moved closer to obtain rewards: either two or three individuals had to pull at exactly the same time at separate bars. To coordinate with two partners was harder than with only one, but the apes had no trouble either way. They were sitting spaced out but in full view of one another. Since the whole group was present, there were many possible partner configurations. The apes could decide who to work with while also being on the alert for competitors, such as dominant males or females, as well as freeloaders who might steal rewards without doing any work. They could freely exchange information and freely choose partners, but also freely compete. No large-scale experiment of this kind had ever been tried.

If it is true that chimps can’t overcome competition, the test should produce total chaos! The colony should descend into a bickering bunch of apes, fighting over rewards and chasing one another away from the test site. Competitiveness should kill all shared objectives. I knew chimps long enough, however, that I didn’t worry much about the outcome of this test; I had studied conflict resolution among them for decades. Despite their poor reputation, I had seen too many scenes of chimpanzees trying to keep the peace and reduce tensions to worry that they would all of a sudden abandon such efforts.

Since Malini and the rest of us wished to see if the chimps could figure out the task on their own, she gave them no pretraining at all. All they knew was that there was a new apparatus and that food was associated with it. They proved remarkably quick learners, realizing that they had to work together and mastering both two-way and three-way pulls within days. Sitting next to one of the pull-bars, Rita would look up at her mother, Borie, who was asleep in a nest on top of a tall climbing frame. She’d climb up all the way to poke Borie in her ribs until she would come down with her. Rita would head for the apparatus, all the while looking over her shoulder to make sure Mom was following. Sometimes we had the impression that the chimps had reached an agreement without us knowing how. Two of them would walk side by side out of the night building, which is quite a distance away, and together head straight for the apparatus, as if they knew exactly what they were going to do. Talk about shared intentionality!

The main point of the study was to see if the apes would compete or cooperate. Clearly, cooperation won big time. We saw some aggression but virtually no injuries. Most fights were low level, such as pulling at someone to drag him or her away from the apparatus, chasing someone off, or throwing sand. Individuals also tried to gain access by grooming one of the pullers until this individual allowed them to take their spot. Cooperation at the apparatus went on almost nonstop, resulting in a total of 3,565 joint pulls.42 Freeloaders were avoided and occasionally punished for their activities, while overly competitive individuals quickly found out how unpopular their behavior made them. The experiment was conducted over many months, affording plenty of time for all the chimps to learn that tolerance paid off in terms of finding partners to work with. In the end, we found proof in the pudding that chimpanzees are highly cooperative. They have no trouble whatsoever regulating and dampening strife for the sake of achieving shared outcomes.

One possible reason that the behavior we observed was more in line with what is known from the natural habitat may be our colony’s background: by the time we tested them, our chimps had lived together for almost four decades. This is a long time by any standard, resulting in an unusually well-integrated group. But when we recently tested a newly formed group, in which many individuals had known one another for only a few years, we found the same high level of cooperation and low level of aggression. In other words, chimpanzees are generally good at conflict management for the sake of cooperation.

The current reputation of chimpanzees as violent and belligerent—“demonic” even—is almost entirely based on the way they treat members of neighboring groups in the wild: they occasionally carry out brutal attacks over territory. This fact has tainted their image, even though lethal combat is so rare that it took decades for scientists to agree on its occurrence. The rate of fatalities at any given field site is on average once every seven years.43 Moreover, it is not as if this behavior sets chimpanzees apart from ourselves. So why is it used as an argument against their cooperative nature, whereas in our own species intergroup warfare is rightly viewed as a collective enterprise? The same holds for chimpanzees—they almost never attack neighbors on their own. It is time for us to see them for what they are: talented team players who have no trouble suppressing conflicts within their group.

A recent experiment at the Lincoln Park Zoo in Chicago confirmed their cooperative skills. Scientists let a group of chimpanzees fish with dipsticks for ketchup that was stored in the holes of an artificial “termite” mound. At the beginning of the experiment, there were enough holes for all members to feed independently, but then the number of holes was reduced by one each day, until there were very few left. Since each hole was monopolizable, it was thought that the chimps would compete and squabble over access to the dwindling resource. But nothing of the kind happened. They adjusted to their new situation by doing the exact opposite: they peacefully gathered around the remaining holes—usually two at a time, sometimes in trios—dipping their sticks into them in alternation, each chimp politely awaiting his or her turn. Instead of a rise in conflict, all the scientists observed was sharing and turn taking.44

When two or more intelligent, cooperative species meet around food resources, the outcome may also be cooperation rather than competition. Each species knows how to take advantage of the other. Fishing cooperatives, in which humans and cetaceans (whales and dolphins) work together, are probably thousands of years old, having been reported from Australia and India to the Mediterranean and Brazil. In South America they operate on the mud shores of lagoons. Fishermen announce their arrival by slapping the water, upon which bottlenose dolphins emerge to herd mullet toward them. The fishers wait for a signal from the dolphins, such as a distinctive type of dive, to throw their nets. Dolphins also do such herding among themselves, but here they drive the fish toward the fishermen’s nets. The men know their dolphin partners individually, having named them after famous politicians and soccer players.

Even more spectacular are the cooperatives between humans and killer whales. When whaling still occurred around Twofold Bay, in Australia, orcas would approach the whaling station to perform conspicuous breaching and lobtailing that served to announce the arrival of a humpback whale. They would herd the large whale into shallow waters close to a whaling vessel, allowing the whalers to harpoon the harassed leviathan. Once the whale was killed, the orcas would be given one day to consume their preferred delicacy—its tongue and lips—after which the whalers would collect their prize. Here too humans gave names to their preferred orca partners and recognized the tit-for-tat that is the foundation of all cooperation, human as well as animal.45

There is only one area in which human cooperation goes well beyond what we know of other species: its degree of organization and scale. We have hierarchical structures to set up projects of a complexity and duration not found elsewhere in nature. Most animal cooperation is self-organized in that individuals fulfill roles according to their capacities. Sometimes animals coordinate as if they have agreed on a task division beforehand. We do not know how shared intentions and goals are communicated, but they do not seem to be orchestrated from above by leaders, as in humans. We develop a plan and put a hierarchy in place to manage its execution, which allows us to lay a railroad track across the country or build a huge cathedral that takes generations to complete. Relying on age-old evolved tendencies, we have shaped our societies into complex networks of cooperation that can take on projects of an unprecedented magnitude.

Fishy Cooperation

Cooperation experiments often ask cognitive questions. Do the actors realize they need a partner? Do they know the partner’s role? Are they prepared to share the spoils? If one individual were to hog all the benefits, this obviously would imperil future cooperation. So we assume that animals watch not only what they get but also what they get compared to what their partner gets. Inequity is something to worry about.

This insight inspired an immensely popular experiment that Sarah Brosnan and I conducted with pairs of brown capuchins. After they performed a task, we rewarded both monkeys with cucumber slices and grapes after determining that they all favored the latter over the former. The monkeys had no trouble with the task if they received identical rewards, even if they both got cucumber. But they were vehemently opposed to unequal outcomes, if one got grapes and the other got cucumber. The cucumber monkey would contentedly munch on her first slice, but after noticing that her companion was getting grapes, she would throw a tantrum. She’d ditch her measly veggies and shake the testing chamber with such agitation that it threatened to break apart.46

Refusing perfectly fine food because someone else is better off resembles the way humans react in economic games. Economists call this response “irrational,” since getting something is by definition better than getting nothing. No monkey, they say, should ever refuse food that she’d normally eat, and no human should reject a small offer. One dollar is still better than no dollar. Sarah and I are unconvinced that this kind of reaction is irrational, though, since it seeks to equalize outcomes, which is the only way to keep cooperation flowing. Apes may even go further than monkeys in this respect. Sarah found that chimpanzees sometimes protest inequity that goes the other way. They object not only to getting less than the other but also to getting more. Grape receivers may reject their own advantage! This obviously brings us close to the human sense of fairness.47

An odd couple of hunters: a coral trout and a giant moray eel prowl together around the reef.

Without going into further details, something encouraging happened in these studies. They were soon extended to other species, including outside the primates. It is always a sign of a field’s maturity when it expands. Researchers who applied inequity tests to dogs and corvids found reactions similar to those of the monkeys.48 Apparently, no species can escape the logic of cooperation, whether it involves the selection of good partners or the balance between effort and payoff.

The generality of these principles is best illustrated by the work on fish by Redouan Bshary, a Swiss ethologist and ichthyologist. For years Bshary has been enchanting us with observations of the interplay and mutualism between small cleaner wrasses and their hosts, the large fish from which the cleaners nibble away ectoparasites. Each cleaner fish owns a “station” on a reef with a clientele, which come and spread their pectoral fins and adopt postures that offer the cleaner a chance to do its job. In perfect mutualism, the cleaner removes parasites from the client’s body surface, gills, and even the inside of its mouth. Sometimes the cleaner is so busy that clients have to wait in queue. Bshary’s research consists of observations on the reef but also experiments in the laboratory. His papers read much like a manual for good business practice. For example, cleaners treat roaming fish better than residents. If a roamer and a resident arrive at the same time, the cleaner will service the roamer first. Residents can be kept waiting since they have nowhere else to go. The whole process is one of supply and demand. Cleaners occasionally cheat by taking little bites of healthy skin out of their client. Clients don’t like this and jolt or swim away. The only clients that cleaners never cheat are predators, which possess a radical counterstrategy: to swallow them. The cleaners seem to have an excellent understanding of the costs and benefits of their actions.49

In a set of studies in the Red Sea, Bshary observed coordinated hunting between the leopard coral trout—a beautiful reddish-brown grouper that can grow to three feet in length—and the giant moray eel. These two species make a perfect match. The moray eel can enter crevices in the coral reef, whereas the trout hunts in the open waters around it. Prey can escape from the trout by hiding in a crevice and from the eel by entering open water, but it cannot get away from the two of them together. In one of Bshary’s videos, we see a coral trout and a moray eel swimming side by side like friends on a stroll. They seek each other’s company, with the trout sometimes actively recruiting an eel through a curious head shake close to the eel’s head. The latter responds to the invitation by leaving its crevice and joining the trout. Given that the two species don’t share the prey with each other but swallow it whole, their behavior seems a form of cooperation in which each achieves a reward without sacrificing anything for the other. They are out for their own gain, which they attain more easily together than alone.50

The observed role division comes naturally to two predators with different hunting styles. What is truly spectacular is that the entire pattern—two actors who seemingly know what they are going to do and how it will benefit them—is not one we usually associate with fish. We have lots of cognitively high-level explanations for our own behavior and find it hard to believe that the same might apply to animals with much smaller brains. But lest one think that the fish are showing a simplified form of cooperation, Bshary’s recent work challenges this notion. Coral trout were presented with a fake moray eel (a plastic model capable of performing a few actions, such as coming out of a tube) that was able to help them catch fish. The setup followed the same logic as the pulling tests in which chimpanzees recruit help when needed, but not if they can complete the task alone. The trout acted in every way similar to the apes and were equally adept at deciding on their need for a partner.51

One way to look at this outcome is to say that chimpanzee cooperation may be simpler than we thought, but another is to say that fish may have a better understanding of how cooperation works than we have been willing to assume. Whether all this boils down to associative learning by the fish remains to be seen; if it does, then any kind of fish should be able to develop this behavior. That seems doubtful, and I agree with Bshary that a species’s cognition is tied to its evolutionary history and ecology. Combined with field observations of cooperative hunting between coral trout and moray eels, the experiment suggests a cognition that suits the hunting techniques of both species. Since the trout takes most of the initiatives and decisions, it may all depend on the specialized intelligence of only one species.

These exciting excursions into nonmammals fit the comparative approach that is the hallmark of evolutionary cognition. There is no single form of cognition, and there is no point in ranking cognitions from simple to complex. A species’s cognition is generally as good as what it needs for its survival. Distant species that face similar needs may arrive at similar solutions, as also happened in the domain of Machiavellian power strategies. After my discovery of divide-and-rule tactics in chimpanzees, and Nishida’s confirmation of their use in the wild, we now have a report on ravens.52 It is perhaps no accident that it came from a young Dutchman, Jorg Massen, who spent years with the chimps at Burgers’ Zoo before he set out to follow wild ravens in the Austrian Alps. There he observed many separating interventions in which one bird would interrupt a friendly contact between others, such as mutual preening, either by attacking one of them or by inserting itself between them. The intervener gained no direct benefits (there was no food or mating at stake) but did manage to ruin a bonding session between others. Bonds are important to ravens, because as Massen explains, their status depends on them. High-ranking ravens are generally well bonded, whereas the middle category are loosely bonded, and the lowest birds lack special bonds. Since interventions were mostly carried out by well-bonded birds targeting loosely bonded ones, their main goal may have been to prevent the latter from establishing friendships in order to rise in status.53 This begins to look a lot like chimpanzee politics, which is exactly what one would expect in a large-brained species with a healthy power drive.

Jumbo Politics

We tend to think of elephants as matriarchal, and this is entirely correct. Elephant herds consist of females with young, occasionally followed around by one or two grown bulls eager to mate. The bulls are only hangers-on. It is hard to apply the term politics to these herds, since the females are ranked by age, family, and perhaps personality, all of which traits are stable. There isn’t much room for the status competition and the opportunistic making and breaking of alliances that marks political strife. For this, we have to go to the males, also in the elephant.

For the longest time, bull elephants have been viewed as loners who travel up and down the savanna and occasionally get behaviorally transformed by the state of musth. Jolted by a twentyfold increase in testosterone, a bull changes into a sort of spinach-eating Popeye, a self-confident jerk ready to fight anyone in his path. Not many animals have such a physiological oddball thrown into their social system. But now we learn from the work by American zoologist Caitlin O’Connell in Estosha National Park, in Namibia, that there is more going on. African elephant bulls are far more sociable than assumed. They may not move in herds like the cows—who stick together to keep predators from bringing down their young—but they know one another individually and have leaders, followers, and semipermanent associations.

In some ways, O’Connell’s descriptions remind me of primate politics, but at other times they sound odd due to the strange ways elephants communicate. For example, a leading bull wary of another may drop his penis during a butt-jiggling retreat. What is going on here? He is awkwardly walking backward while his penis—which is pretty obvious in an elephant—serves as a signal. Why not retract it at such moments? They drop it in submission, or as O’Connell calls it, “supplication.”

On the dominance side as well, their behavior is highly unusual. Here a description of a musth display:

He was so agitated that he walked over to the place where Greg had previously defecated and performed a dramatic musth display over the offending pile of feces, dribbling urine and curling his trunk over his head, waving his ears and prancing with his front legs in the air, mouth wide open.54

It used to be thought that the older and larger a bull, the higher-ranking he’d be. If so, this system would be rather inflexible. O’Connell, however, documented status reversals. One leading male gradually lost his ability to rally followers. He would fan his ears and emit a let’s-go rumble, but no one would pay any heed the way they had done in earlier years. His coalition was falling apart, whereas it previously had shown impressive cohesion. One sign of an intact “boys’ club” is that the dominant bull’s vocalizations are echoed by the bulls around him. A subordinate’s call starts at the moment the dominant’s call ends, followed by yet another subordinate, and yet another, resulting in a cascade of repeated calls among the bulls that signal to the rest of the world that they are tight and united.

Elephant coalitions are subtle, and everything these animals do seems a slow-motion movie to the human eye. Sometimes two bulls will deliberately stand right next to each other with ears out, so as to indicate to an opponent that it is time to leave the waterhole. These coalitions dominate the scene, usually arranged around a clear leader. Other bulls come to pay their respect to him, approaching him with outstretched trunk, quivering in trepidation, dipping the tip into his mouth in an act of trust. After performing this tense ritual, the lower-ranking bulls relax as if a burden has been taken off their shoulders. These scenes are reminiscent of how dominant male chimpanzees expect subordinates to crawl in the dust while uttering submissive grunts, not to mention human status rituals, such as kissing the ring of the don, or Saddam Hussein’s insistence that his underlings stick their nose under his armpit. Our species is quite creative when it comes to reinforcement of the hierarchy.

We are familiar enough with these processes to recognize them in other animals. As soon as power is based on alliances rather than individual size or force, the door opens to calculated strategies. Given elephant intelligence in other domains, there is every reason to expect pachyderm society to be as complex as that of other political animals.

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