by Carl Sagan
The hamadryas male’s larger size and ferocious temperament doubtless are useful when the troop is imperilled by predators, or in conflict with other groups. But, as in the rest of the animal kingdom, when there are conspicuous differences in stature between the sexes (usually, it’s the males who are bigger), there’s exploitation and abuse of the smaller and weaker (usually the females).* Another distinction of the hamadryas baboons is that, alone among nonhuman primates so far as we know, two groups have been observed to ally themselves in combat against a third.4
Among savanna baboons, where the size difference between the sexes is not so striking, there are no harems. They are great walkers; it’s not unknown for a troop to cover twenty miles a day. Unlike chimps and hamadryas baboons, here it’s the male who leaves the natal troop around puberty—again, probably as an evolutionary device to avoid incest, and genetically to connect semi-isolated populations. When he attempts to enter a new troop, objections are likely to be raised by the resident males. Acceptance by the group often requires the time-honored method of submission, bluff, coercion, and alliance-making in the male hierarchy. But in many cases another strategy works well: make friends with a particular female in the troop and her children. He grooms her. He baby-sits and cares for her young. No killing off the young here in order to bring her into ovulation, as with rats and lions. If all goes well, she sponsors his entry into the troop. We can imagine a certain exhilaration as, gingerly, he attempts to enter the new community, his gaffes and old enemies left behind, a clean slate before him, and success dependent almost entirely on his social skills.
The males are more flighty and tempestuous than the females. Social stability is mainly provided on the female side. Indeed, since savanna baboon males are transients, the only hope for coherent group structure lies with the females. In all things, female baboons are comparatively conservative; it is the testosterone-pumped males who take the risks.
The female dominance hierarchy is largely hereditary. Daughters of alpha females are given unusual deference, even as juveniles, and have a good chance of achieving alpha status when they grow up. Every close relative of the dominant female may outrank every other member of the troop—a royal family. Submission and dominance in the female hierarchy of savanna baboons and many other monkey species is conveyed in the time-honored idiom of presenting and mounting, the heterosexual metaphor again adapted to another purpose.
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For reasons not fully understood but worth speculating on, much more attention—at least in public discussion and until recently—has been given to hamadryas baboons than to their savanna cousins. Sometimes the impression has been left that hamadryas behavior is representative of all nonhuman primates, or even all primates. For example, the hamadryas males, in a species in which nothing else is owned, have a clear sense of females as private property. But this is by no means true of all primates. The hamadryas baboons, it turns out, provide perhaps the most extreme example of hierarchy and brutality in the entire order of the primates. This behavior was especially marked under a set of cruel circumstances devised by humans who meant them no harm:
Living with apes or monkeys in the wild did not much appeal to primatologists until recently. More typical was an expedition back to his native South Africa by Solly Zuckerman, anatomist to the Zoological Society of London:
On the 4th of May, 1930, I succeeded in collecting on a farm near Grahamstown in the Eastern Province twelve adult females from one troop of baboons. Four of these were non-pregnant. Five were pregnant; one had an embryo 2.5 mm. in length; another one of 16.5 mm.; the third one of 19 mm.; the fourth one of 65 mm.; and the fifth an apparently full term male foetus with a crown-rump length of 230 mm. Three were lactating, and their babies were caught alive. One infant was estimated to be four months old, and the other two were each about two months.5
He dutifully noted how much fresh semen there was at various depths within the reproductive tracts of his female victims; “collected,” it turns out, is a euphemism for “killed.” Baboons had been officially declared “vermin” in South Africa, because they’re smart enough to defeat the efforts of farmers to safeguard their crops. A bounty was paid for each dead baboon. So a few baboons “collected” for science hardly mattered, compared with the wholesale slaughter being organized by the farmers. Through such studies Zuckerman “had the luck to discover from post-mortem study that ovulation in mature females occurs in the middle of the monthly sexual cycle.”6 The corresponding discovery about the human menstrual cycle was made around the same time.
He had long been interested in the standing of humans among the primates, and was dissecting baboons in South Africa while still a teenager.7 But he was not wholly unmoved by the plight of the hunted baboons, and later quoted this early-twentieth-century account:
Hugging her baby tight to her breast, she regarded us with a world of sadness in her eyes, and with a gasp and shudder she died. We forgot for the moment that she was but a monkey, for her actions and expression were so human, that we felt we had committed a crime. Muttering an oath, my friend turned and walked rapidly off, vowing that this was the last time he would shoot a monkey. “It isn’t sport, it’s downright murder,” he declared, and I fervently agreed with him.8
If you wanted to meet a baboon—and you lived in a country where they didn’t roam about in the wild—you could always go to the local zoo and see the bedraggled and deracinated inmates, lifers pent up in tiny cubicles. After World War I, some European zoos thought it would be better, as well as more “humane,” if a large number of baboons could be gathered together in a partly open enclosure admitting observation by city-bound primatologists. The London Zoo was among them, and Dr. Zuckerman was playing a central role in the organization of one of these multiyear experiments:
In the spring of 1925, about one hundred hamadryas baboons were introduced into moat-bordered Monkey Hill, about 33 by 20 meters in area. So each baboon had, on average, less than 7 square meters, or some 60 square feet, indeed about the size of a small prison cell. It had been intended that this be an all-male group, but through an “accidental inclusion” six of the hundred baboons proved to be female. After a time, the oversight was rectified and the group was augmented by a further thirty females and five males. By late 1931, 64% of the males were dead, and 92% of the females:
Of the thirty-three females that died, thirty lost their lives in fights, in which they were the prizes fought for by the males. The injuries inflicted were of all degrees of severity Limb-bones, ribs, and even the skull, have been fractured. Wounds have sometimes penetrated the chest or abdomen, and many animals showed extensive lacerations in the ano-genital region … The fight in which the last of these females lost her life was so protracted and repellent—from the anthropocentric point of view—that the decision was made to remove the five surviving females from the Hill … The very high percentage of females killed in the London Colony suggests. . that the social group of which they formed a part was in some way unnatural.9
Despite this last qualification, the hamadryas colony at the London Zoo reinforced a widespread belief in an unconstrained Darwinian struggle for existence. Even though baboons would quickly have exterminated themselves from the world if the events at Monkey Hill were characteristic of life in the wild, many people felt that they had now glimpsed Nature in the raw, a brutal Nature, red in claw and fang, a Nature from which we humans are insulated and protected by our civilized institutions and sensibilities. And Zuckerman’s vivid descriptions of the unrestrained sex lives of the baboons—he was one of the first to stress that baboon social organization may be determined largely by sexual considerations—increased the contempt that many humans felt toward the other primates.
What had gone wrong on Monkey Hill? First, almost all of the baboons introduced into the “colony” were unknown to one another. There was no long-term mutual habituation, no prior establishment of dominance hierarchies, no common understanding in these harem-obsessed males of who
was to have many females and who none at all. No kinship-based female dominance hierarchy had been established. Unlike the situation in the wild, there were many more males than females. Finally, these baboons were crowded together to a degree rarely experienced in their natural state.
Because of their powerful jaws and spectacular canines, baboon males within a troop hardly ever fight among themselves in earnest, although corporal punishment is visited on the females for the slightest infractions. But in the London Zoo, dominance hierarchies had to be established, dedicated attempts were made to steal females, escape from a formidable attacker was cut off by the moat, and the calming influence of many sexually compliant females was almost entirely wanting. The result was carnage. In all six and a half years, only one infant survived. When the males would fight over them, the adult females would listlessly wait, as if “paralysed.” The battered, lacerated, punctured females would be sexually used by a quick succession of males.
But the females were not mere passive instruments:
[W]hen her overlord’s back was turned she quickly presented to the bachelor attached to her party, who mounted for a moment. The overlord then slightly turned his head, whereupon the female rushed to him, her body low to the ground, presenting and squealing, and threatening her seducer with grimaces and with quick thrusts of her hands on the rocks. This behaviour immediately stimulated an attack by the overlord … Closely pursued, the bachelor fled. On another occasion the same female was left alone for forty seconds while her overlord chased a bachelor around Monkey Hill. In that space of time she was mounted and penetrated by two males to whom she had presented. Both of these immediately made off after their contact with the female, who again responded to the return of her male in the manner described above.10
When females were killed, the males would continue to drag them around, one male after another, to fight over them, and to copulate with their corpses. When the keepers, grimly watching this necrophilial tableau unfold, felt it necessary—for “anthropocentric” reasons—to enter the compound and remove the dead body, the males, in concert, would violently object and resist. Zuckerman, writing back then in the 1920s, used and may have coined the phrase “a sexual object”11 in describing the lot of the female baboon.
We’ve seen in Calhoun’s experiments with rats that—even when there’s plenty of food, even when there are as many males as females—severe crowding induces violent and other modes of behavior that many would describe as aberrant and maladaptive. We’ve also seen in the Arnhem chimp colony how, under similar circumstances, new modes of behavior come to the fore to inhibit violence. From the baboons in the London Zoo we learn that if you take a species given to sexual violence in the best of conditions, provide a small number of sexual prizes to be fought over, arrange to have no pre-existing social order in which the animals know where they fit, and now crowd everybody together with no hope of escape, mayhem is the likely outcome. Monkey Hill reveals a deadly intersection of sex, hierarchy, violence, and crowding that may or may not apply to other primates.*
In Nature, as Zuckerman recognized, hamadryas baboons live much more peaceably. Dominant males are surrounded by a small corona of females, their offspring, and a few affiliated “bachelor” males. These harems wander over the landscape in bands, collecting food. Hundreds of baboons, a kind of gathering of the tribes, camp out each night near one another on sleeping cliffs. Fights to the death for possession of the females (or for any other reason) hardly ever happen. Everyone knows his, and especially her, place. The females are of course routinely abused, bitten on average once a day, but not so deeply as to draw blood. They are certainly not all killed off because they might be interested in other males, as happened in the London Zoo.
Hamadryas baboons in very small groups behave very differently: A bachelor baboon male watches a couple—on their first date—in an adjacent cage. Days go by, and he is forced to observe their deepening sexual relationship while he sits alone. When he’s then introduced into their cage, he makes no effort to attack the male or to lure the female away. He respects their relationship. He looks away when they have sex. He is a model of rectitude and circumspection, even if he’s of larger stature than either.12
Unsurprisingly, there are ways of arranging a primate society so its structure collapses and almost everybody dies. Shall we think of primates who find themselves in such circumstances as criminals? Are they accountable for their actions? Do they have free will? Or shall we attribute the bulk of the responsibility for what happens to those through whose miscalculation the social environment was established? For a society to be successful, it must be consonant with the nature and character of the individuals who must live in it. If those contriving social structures overlook who these individuals are, or sentimentalize their nature, or are incompetent social engineers, disaster can result.
Zuckerman has consistently argued that almost nothing about human nature or evolution can be learned by studying monkeys and apes—quite the opposite of many students of animal behavior who believe that understanding primates might provide a direct route to understanding humans: “[M]y unbending critical attitude to attempts to explain human behavior by analogies from the animal world must have been acquired at a very early age.”13 He describes Konrad Lorenz, Desmond Morris, and Robert Ardrey—who popularized, with at least some excesses, the idea that we have something to learn about ourselves from studying other animals—as “three writers who are equally adept at devising superficial analogies.”14
As “Prosector” of the London Zoo—the officer in charge of animal autopsies—Zuckerman later submitted the manuscript of a book, entitled The Social Life of Monkeys and Apes, for approval to his superior in the zoo’s dominance hierarchy. It was promptly rejected on grounds of displaying an undecorous explicitness on matters sexual (for example, “The overlord’s attention is caught by the perineal region of one of his females, usually when her sexual skin is swollen. He bends his head forward, his hand reaches out, his lips and tongue move and, having thus stimulated the sexual response in the female, he mounts and copulates”15). Zuckerman offered the book for publication anyway. In his autobiography, From Apes to Warlords, published forty-six years later—amidst much vivid detail of those years—he makes only the most tangential reference to the events at Monkey Hill.
At the start of World War II Zuckerman studied the consequences of aerial bombardment on civilian populations—his anatomical knowledge could there be put to good use. He soon moved on to analyzing the effectiveness of aerial bombing in the accomplishment of strategic goals, where his skeptical proclivities came in handy: The RAF’s Bomber Command (and the U.S. Army Air Corps), he found, had consistently exaggerated the potential of massive aerial bombardment to lessen the enemy’s will to fight and to shorten the war.
After the war Zuckerman headed the London Zoo, and through a few turns in his career wound up to be the principal scientific adviser to the British Ministry of Defence, where his expertise in understanding dominance hierarchies may have been germane. Created a Life Peer, Lord Zuckerman worked for many years to slow the nuclear arms race.
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Baboons as a whole represent only one small corner in the vast arena of primate behavior. We could just as easily have focused
on any of a number of lemur species, species in which females rather routinely dominate males. We could have decided to make an example of the shy and nocturnal owl monkey … where males and females cooperate in child care with the male playing the major role in carrying and protecting the infant, or we could have focused on the gentle South American monkeys known as “muriqui” … who specialize in avoiding aggressive interactions, or any of a host of other primate species in which we now know that females play an active role in social organization.16
Consider the gibbon. Its preternaturally long arms permit it to make great balletic leaps through the canopy of the forest—sometimes ten meters or more from branch to branch—that put champion human gymnasts to sh
ame. Gibbons are, apparently without exception, monogamous. They marry for life. They produce haunting songs heard a kilometer or more away. Adult males often sing long solos in the darkness just before sunrise. Bachelors sing longer than old married males, and at a different time of day. Wives prefer duets with their husbands. Widows bear their grief in silence and sing no more.
Gibbons are also territorial and their matins serve to keep intruders away. A nuclear family, typically parents and two children, tends to control a small turf. Defense of the home territory is accomplished not so much by throwing stones or raining blows as by singing anthems. Perhaps there are cadences, timbres, frequencies, and amplitudes that other gibbons, contemplating a little poaching, find especially impressive and daunting. At least sometimes, an aging father will confer responsibility for territorial defense on his adolescent son, passing the patriotic torch on to the younger generation. In other equally poignant instances, adolescents are banished from the home territory by the parents, perhaps to avoid the temptations of incest. Adult males and females behave pretty much alike, and have nearly equal social status. Primatologists describe the females as “codominant,” and the partners in a marriage as “relaxed” and “tolerant.”17
Gibbon life seems downright operatic. It’s easy to conjure up feverish love solos, duets sung in praise of marital felicity, and ritual intimidation chants cast into the forest night: “We’re here, we’re tough, we sing good songs. Better leave our turf alone.” Perhaps there are gibbon Verdis singing power-transfer arias, rich with pathos, soulful lamentations on the passing of glory and of time.
Or consider the bonobo. This is a reclusive species or subspecies of chimpanzee that lives in a single group in Central Africa, south of the Zaire River.18 Bonobos have certain traits that render them conventionally ineligible for the local zoo, which may be one reason that they’re not nearly so well known as the common chimp we’ve described in the preceding chapters. Bonobos, given the Linnaean name Pan paniscus, are also called pygmy chimpanzees; they’re smaller and more slender and their faces protrude less than the usual variety, Pan troglodytes, which we’ll here and there continue to describe simply as chimpanzees.* Bonobos often stand up and walk on two legs. (They have a kind of webbing of skin between their second and third toes.) They stride with their shoulders squared and do not slouch as much as chimps do. “When bonobos stand upright,” writes de Waal, “they look as if they had walked straight out of an artist’s impression of prehistoric man.”19
