sound utterly repugnant to do a cost and benefit analysis of murder, but such analyses nevertheless help one understand why murder appears to characterize only some animal species.
In non-social species, murders are necessarily just of one individual by another. However, in social carnivorous species, like lions, wolves, hyenas, and ants, murder may take the form of coordinated attacks by members of one troop on members of a neighbouring troop—that is, mass killings or 'wars'. The form of war varies among species.1 Males may spare and mate with neighbouring females, kill the infants, and drive off (langur monkeys) or even kill (lions) neighbouring males; or both males and females may be killed (wolves). As one example, here is
Hans Kruuk's account of a battle between two hyena clans in Tanzania's Ngorongoro Crater: About a dozen of the Scratching Rock hyenas, though, grabbed one of the Mungi males and bit him wherever they could— especially in the belly, the feet, and the ears. The victim was completely covered by his attackers, who proceeded to maul him for about ten minutes. . The Mungi male was literally pulled apart, and when I later studied the injuries more closely, it appeared that his ears were bitten off and so were his feet and testicles, he was paralyzed by a spinal injury, had arge gashes in the hind legs and belly, and subcutaneous haemorrhages all over.
Of particular interest in understanding our genocidal origins is the behaviour of two of our three closest relatives, gorillas and common chimpanzees. Two decades ago, any biologist would have assumed that our ability to wield tools and to lay concerted group plans made us far more murderous than apes—if indeed apes were murderous at all. Recent discoveries about apes suggest, however, that a gorilla or common chimp stands at least as good a chance of being murdered as the average human. Among gorillas, for instance, males fight each other for ownership of harems of females, and the victor may kill the loser's infants as well as the loser himself. Such fighting is a major cause of death for infant and adult male gorillas. The typical gorilla mother loses at least one infant to infanticidal males in the course of her life. Conversely, thirty-eight per cent of infant gorilla deaths are due to infanticide.
Especially instructive, because it could be documented in detail, was the extermination of one of the common chimpanzee bands that Jane Goodall studied, carried out between 1974 and 1977 by another band. At the end of 1973 the two bands were fairly evenly matched: the Kasakela band to the north, with eight mature males and occupying fifteen square kilometers; and the Kahama band to the south, with six mature males and occupying ten square kilometers. The first fatal incident occurred in January 1974, when six of the Kasakela adult males, one adolescent male, and one adult female left behind the young Kasakela chimps, travelled south, then moved silently and more quickly south when they heard chimp calls from that direction, until they surprised a Kahama male referred to as Godi. One Kasakela male pulled the fleeing Godi to the ground, sat on his head, and pinned out his legs while the others spent ten minutes hitting and biting him. Finally, one attacker threw a large rock at Godi, and the attackers then left. Although able to stand up, Godi was badly wounded, bleeding, and had puncture marks. He was never seen again and presumably died of his injuries.
The next month, three Kasakela males and one female again travelled south and attacked the Kahama male De, who was already weak from a previous attack or illness. The attackers pulled De out of a tree, stamped on him, bit and hit him, and tore off pieces of his skin. A Kahama oestrus female with De was forced to return northwards with the attackers. Two months later De was seen still alive but emaciated, with his spine and pelvis protruding, some fingernails and part of a toe torn off, and his scrotum shrunk to one-fifth of normal size. He was not seen thereafter. In February 1975 five adult and one adolescent Kasakela males tracked down and attacked Goliath, an old Kahama male. For eighteen minutes they hit, bit, and kicked him, stamped on him, lifted and dropped him, dragged him over the ground, and twisted his leg. At the end of the attack Goliath was unable to sit up and was not seen again.
While the above attacks were aimed at Kahama males, in September 1975 the Kahama female Madam Bee was fatally injured after at least four non-fatal attacks over the course of the preceding year. The attack was carried out by four Kasakela adult males, while one adolescent male and four Kasakela females (including Madam Bee's kidnapped daughter) watched. The attackers hit, slapped, and dragged Madam Bee, stamped and pounded on her, threw her to the ground, picked her up and slammed her down, and rolled her downhill. She died five days later. In May 1977 five Kasakela males killed the Kahama male Charlie, but details of the fight were not observed. In November 1977 six Kasakela males caught the Kahama male Sniff and hit, bit, and pulled him, dragged him by the legs, and broke his left leg. He was still alive the next day but was not seen again.
Of the remaining Kahama chimps, two adult males and two adult females disappeared from unknown causes, while two young females transferred to the Kasakela band, which proceeded to occupy the former Kahama territory. However, in 1979 the next band to the south, the larger Kalande band with at least nine adult males, began to encroach on Kasakela territory and may have accounted for several vanished or wounded Kasakela chimps. Similar intergroup assaults have been observed in the sole other long-term field study of common chimps, but not in long-term studies of pygmy chimps.
If one judges these murderous common chimps by the standards of human killers, it is hard not to be struck by their inefficiency. Even though groups of three to six attackers assaulted a single victim, quickly rendered him or her defenceless, and continued the assault for ten to twenty minutes or more, the victim was always still alive at the end of that time. However, the attackers did succeed in immobilizing the victim and often causing eventual death. The pattern was that the victim initially crouched and may have tried to protect his head but then gave up any attempt at defence, and the attack continued beyond the point where the victim ceased moving. In this respect the inter-band attacks differ from the milder fights that often occur within a band. Chimps' inefficiency as killers reflects their lack of weapons, but it remains surprising that they have not learned to kill by strangling, although that would be within their capabilities. Not only is each individual killing inefficient by our standards, but so is the whole course of chimp genocide. It took three years and ten months from the first killing of a Kahama chimp to the band's end, and all killings were of individuals, never of several Kahama chimps at once. In contrast, Australia's settlers often succeeded in eliminating a band of Aborigines in a single dawn attack. Partly, this inefficiency again reflects chimps' lack of weapons. Since all chimps are equally unarmed, killings can succeed only by several attackers overpowering a single victim, whereas Australia's settlers had the advantage of guns over unarmed Aborigines and could shoot many at once. Partly, too, genocidal chimps are much inferior to humans in brainpower and hence in strategic planning. Chimps apparently cannot plan a night attack or a coordinated ambush by a split assault team.
However genocidal chimps do seem to evince intent and unsophisticated planning. The Kahama killings resulted from Kasakela groups proceeding directly, quickly, silently, and nervously towards or into Kahama territory, sitting in trees and listening for nearly an hour, and finally running to Kahama chimps that they detected. Chimps also share xenophobia with us; they clearly recognize members of other bands as different from, and treat them very differently from, members of their own band.
In short, of all our human hallmarks—art, spoken language, drugs, and the others—the one that has been derived most straightforwardly from animal precursors is genocide. Common chimps already carried out planned killings, extermination of neighbouring bands, wars of territorial conquest, and abduction of young nubile females. If chimps were given spears and some instruction in their use, their killings would undoubtedly begin to approach ours in efficiency. Chimpanzee behaviour suggests that a major reason for our human hallmark of group living was defence against other human groups, especially once we acquired weapons and a large enough brain to plan ambushes. If this reasoning is correct, then anthropologists' traditional emphasis on 'man the hunter' as a driving force of human evolution might be valid after all-with the difference that we ourselves, not mammoths, were our own prey and the predator that forced us into group living.
Of the two patterns of genocide commonest among humans, both have animal precedents: killing both men and women fits the common chimpanzee and wolf pattern, while killing men and sparing women fits the gorilla and lion pattern. Unprecedented even among animals, however, is a procedure adopted from 1976 to 1983 by the Argentine military, in the course of killing over 10,000 political opponents and their families, the
