strength and instinct for aggression would gradually come to predominate in the population. Most cultural anthropologists from the 1950s onward rejected the expla- nation of human aggression in terms of instincts, emphasizing instead the social and cultural causes of violence. They pointed out that the amount of aggression tolerated varies widely from one society to another and that individ- uals can become aggressive or peaceful depending on how they are raised. They held up such groups as the Semai of Malaysia (see Robert K. Dentan, The Semai: A Nonviolent People of Malaya [Holt, Rinehart & Winston, 196811) as proof YES: Richard Wranghani and Dale Peterson, from Demonic that culture could create a people who abhorred all forms of aggression and Males: Apes and the Origins or Human Violence (Houghton Mifflin coercion. 'Whatever instinct for aggression humans might have, they argued, Company, 1996) must be very weak indeed. The question behind this issue concerns the nature of human nature. NO: Robert W. Sussman, from "Exploring Our Basic Human Have we a set of innate behavioral predispositions that, when set off by certain Nature," Anthro Notes (Fall 1997) stimuli, are very likely to be expressed? Or, are any such predispositions at best weak tendencies that can be shaped or even negated by cultural conditioning? Many apparently innate behaviors in humans turn out to be highly variable in ISSUE SUMMARY their strength and form. While the sucking instinct of babies operates predict- ably in all newborns, a hypothesized "mothering instinct" seems quite diverse YES: Biological anthropologist Richard Wrangham and science in expression and variable in strength from one woman to another. The ques- writer Dale Peterson maintain that male humans and chimpanzees, tion, then, is whether the hypothesized aggression instinct is a powerful drive our closest nonhuman relatives, have an innate tendency to be that all human males must express in one way or another or a weak and pliable aggressive and to defend their territory by violence. They state that tendency that some males may never act upon. sexual selection, a type of natural selection, has fostered an instinct Richard Wrangham and Dale Peterson argue that human wars and for male aggression because males who are good fighters mate interpersonal violence are driven by inherited behavioral tendencies that have more frequently and sire more offspring than weaker and less evolved under pressure of sexual selection—natural selection of traits that aggressive ones. enhance the reproductive success of one sex. Among both humans and chim- panzees, males *ho are aggressive use their fighting ability to dominate other NO: Biological anthropologist Robert W. Sussman rejects the theory males and to prevent them from mating with the available females. Therefore that human aggression is an inherited propensity, arguing instead the genes causing aggression are passed on to succeeding generations in greater that violence is a product of culture and upbringing. He also rejects the contention that male chimpanzees routinely commit numbers than the genes causing nonaggressive behavior. violent acts against other male chimps. Sussman regards the Robert W. Sussman rejects Wrangham and Peterson's assertion that notion that human males are inherently violent as a Western natural selection favors aggressive human males and that aggressiveness is an cultural tradition, not a scientifically demonstrated fact. inherited tendency rather than a result of environment and upbringing. He contends that human hunter-gatherers and most apes are remarkably non- aggressive, as were our earliest human ancestors, the australopithecines. He h uman history is rife with wars between groups of all types, from clans to sees the evidence that chimpanzee males routinely attack other males as weak, nation-states, and interpersonal violence is common enough that all societies and he questions the relevance of chimpanzee behavior for humans. attempt to control it. But is violence a part of human nature, or is violence These selections raise a number of questions with regard to the nature merely one of many human capabilities that may be either encouraged or dis- and causes of human aggression. How can we determine whether a person's couraged by cultures? aggressive act is due to instinct, upbringing, or both? If male aggression in The question of whether or not humans have an instinct for aggres- humans is based on instinct, how can scholars explain variations in the sion has been around since the formative years of anthropology, and it is amount and type of aggression found in different individuals and cultures? still being debated today. Some nineteenth-century scholars interpreted If male aggression is not based on instinct, why is violence between men so Darwin's concepts of "natural selection" and "survival of the fittest" to widespread? What role did women have in the evolution of an instinct for mean that the strong would kill off the weak. The strongest and most male violence? To what extent can studies of animal behavior be applied aggressive individuals, therefore, would have the most offspring, and their to humans? 16 17 YES / Wrangham and Peterson 19 And yet science has still not grappled closely with the ultimate questions Richard Wrangham raised by the Kahama killings: Where does human violence come from, and and Dale Peterson (9 YES why? Of course, there have been great advances in the way we think about these things. Most importantly, in the 1970s, the same decade as the Kahama killings, a new evolutionary theory emerged, the selfish-gene theory of natural selection, variously called inclusive fitness theory, sociobiology, or more Demonic Males: Apes and the broadly, behavioral ecology. Sweeping through the halls of academe, it revolu- fionized Darwinian thinking by its insistence that the ultimate explanation of Origins of Human Violence any individual's behavior considers only how the behavior tends to maximize genetic success: to pass that individual's genes into subsequent generations. The new theory, elegantly popularized in Richard Dawkins's The Selfish Gene, is Paradise Lost now the conventional wisdom in biological science because it explains animal behavior so well. It accounts easily for selfishness, even killing. And it has come The killer ape has long been part of our popular culture: Tarzan had to escape to be applied with increasing confidence to human behavior, though the from the bad apes, and King Kong was a murderous gorilla-like monster. But debate is still hot and unsettled. In any case, the general principle that behavior before the Kahama observations [in which males of one chimpanzee group evolves to serve selfish ends has been widely accepted, and the idea that killed the males of a neighboring group], few biologists took the idea seriously, humans might have been favored by natural selection to hate and to kill their The reason was simple. There was so little evidence of animals killing members enemies has become entirely, if tragically, reasonable. of their own species that biologists used to think animals killed each other only when something went wrong—an accident, perhaps, or unnatural crowding in Those are the general principles, and yet the specifics are lacking. Most zoos. The idea fit with the theories of animal behavior then preeminent, theo- animals are nowhere near as violent as humans, so why did such intensely ries that saw animal behavior as designed by evolution for mutual good. violent behavior evolve particularly in the human line? Why kill the enemy, Darwinian natural selection was a filter supposed to eliminate murderous rather than simply drive him away? Why rape? Why torture and mutilate? violence. Killer apes, like killers in any animal species, were merely a novelist's Why do we see these patterns both in ourselves and chimpanzees? Those sorts fantasy to most scientists before the 1970s. of questions have barely been asked, much less addressed. And so the behavior of people seemed very, very different from that of Because chimpanzees and humans are each other's closest relatives, such other animals. Killing, of course, is a typical result of human war, so one had to questions carry extraordinary implications, the more so because the study of presume that humans somehow broke the rules of nature. Still, war must have early human ancestry, unfolding in a fervor as we approach the century's end, come from somewhere. It could have come, for example, from the evolution of is bringing chimpanzees and humans even closer than we ever imagined. brains that happened to be smart enough to think of using tools as weapons, as Three dramatic recent discoveries speak to the relationship between chim- Konrad Lorenz argued in his famous book, On Aggression, published in 1963, panzees and humans, and all three point in the same direction: to a past, However it may have originated, more generally war was seen as one of around 5 million years ago, when chimpanzee ancestors and human ancestors the defining marks of humanity: To fight wars meant to be human and apart were indistinguishable. from nature. This larger presumption was true even of nonscientific theories, First, fossils recently dug up in Ethiopia indicate that over 4.5 million such as the biblical concept of an original sin taking humans out of Eden, or years ago there walked across African lands a bipedal ancestor of humans with the notion that warfare was an idea implanted by aliens, as Arthur C. Clarke a head strikingly like a chimpanzee's. imagined in 2001: A Space Odyssey. In science, in religion, in fiction, violence Second, laboratories around the world have over the last decade demon- and humanity were twinned. strated chimpanzees to be genetically closer to us than they are even to gorillas, The Kahama killings were therefore both a shock and a stimulus to despite the close physical resemblance between chimpanzees and gorillas.