Are human beings innately aggressive?

This is a favorite question of college seminars and cocktail party conversations, and one that raises emotion in political ideologues of all stripes. The answer to it is yes.

Throughout history, warfare, representing only the most organized technique of aggression, has been endemic to every form of society, from hunter-gatherer bands to industrial states.

During the past three centuries a majority of the countries of Europe have been engaged in war during approximately half of all the years; few have ever seen a century of continuous peace. Virtually all societies have invented elaborate sanctions against rape, extortion, and murder, while regulating their daily commerce through complex customs and laws designed to minimize the subtler but inevitable forms of conflict. Most significantly of all, the human forms of aggressive behavior are species-specific: although basically primate in form, they contain features that distinguish them from aggression in all other species…

Theoreticians who wish to exonerate the genes and blame human aggressiveness wholly on perversities of the environment point to the tiny minority of societies that appear to be nearly or entirely pacific. They forget that innateness refers to the measurable probability that a trait will develop in a specified ‘set of environments, not to the certainty that the trait will develop in all environments. By this criterion human beings have a marked hereditary predisposition to aggressive behavior…

Like most other mammals, human beings display a behavioral scale, a spectrum of responses that appear or disappear according to particular circumstances… Because there is a complex scale instead of a simple, reflex-like response, psychoanalysts and zoologists alike have had an extraordinarily difficult time arriving at a satisfactory general characterization of human aggression…

Freud interpreted the behavior in human beings as the outcome of a drive that constantly seeks release. Konrad Lorenz, in his book On Aggression, modernized this view with new data from the studies of animal behavior. He concluded that human beings share a general instinct for aggressive behavior with other animal species. This drive must somehow be relieved, if only through competitive sports…

Both of these interpretations are essentially wrong. Like so many other forms of behavior and “instinct,” aggression in any given species is actually an ill-defined array of different responses with separate controls in the nervous system.

No fewer than seven categories can be distinguished: the defense and conquest of territory, the assertion of dominance within well-organized groups, sexual aggression, acts of hostility by which weaning is terminated, aggression against prey, defensive counterattacks against predators, and moralistic and disciplinary aggression used to enforce the rules of society.

Rattlesnakes provide an instructive example of the distinction between these basic categories. When two males compete for access to females, they intertwine their necks and wrestle as though testing each other’s strength, but they do not bite, even though their venom is as lethal to other rattlesnakes as it is to rabbits and mice. When a rattlesnake stalks its prey it strikes from any number of positions without advance warning. But when the tables are turned and the snake is confronted by an animal large enough to threaten its safety, it coils, pulls its head forward to the center of the coil in striking position, and raises and shakes its rattle. Finally, if the intruder is a king snake, a species specialized for feeding on other snakes, the rattlesnake employs a wholly different maneuver: it coils, hides its head under its body, and slaps at the king snake with one of the raised coils. So to understand the aggression of rattlesnakes or human beings it is necessary to specify which of the particular forms of aggressive behavior is of interest…

Continuing research in zoology has also established that none of the categories of aggressive behavior exists in the form of a general instinct over broad arrays of species. Each category can be added, modified, or erased by an individual species during the course of its genetic evolution, in the same way that eye color can be altered from one shade to another or a particular skin gland added or eliminated. When natural selection is intense, these changes can occur throughout an entire population in only a few generations. Aggressive behavior is in fact one of the genetically most labile of all traits… There is no evidence that a widespread unitary aggressive instinct exists.

The reason for the absence of a general aggressive instinct has been revealed by research in ecology. Most kinds of aggressive behavior among members of the same species are responsive to crowding in the environment. Animals use aggression as a technique for gaining control over necessities, ordinarily food or shelter, that are scarce or are likely to become so at some time during the life cycle. They intensify their threats and attack with increasing frequency as the population around them grows denser. As a result the behavior itself induces members of the population to spread out in space, raises the death rate, and lowers the birth rate. In such cases aggression is said to be a “density-dependent factor” in controlling population growth. As it gradually increases in intensity, it operates like a tightening valve to slow and finally shut off the increase in numbers…

Other species, in contrast, seldom or never run short of the basic necessities of life… Such animals are typically pacific toward each other, because they rarely grow numerous enough for aggressive behavior to be of any use to individuals. And if aggression confers no advantage, it is unlikely to be encoded through natural selection into the innate behavioral repertory of the species…

The clear perception of human aggressive behavior as a structured, predictable pattern of interaction between genes and environment is consistent with evolutionary theory. It should satisfy both camps in the venerable nature-nurture controversy. On the one hand it is true that aggressive behavior, especially in its more dangerous forms of military action and criminal assault, is learned. But the learning is prepared. We are strongly predisposed to slide into deep, irrational hostility under certain definable conditions. With dangerous ease hostility feeds on itself and ignites runaway reactions that can swiftly progress to alienation and violence. Aggression does not resemble a fluid that continuously builds pressure against the walls of its containers, nor is it like a set of active ingredients poured into an empty vessel. It is more accurately compared to a preexisting mix of chemicals ready to be transformed by specific catalysts that are added, heated, and stirred at some later time.

The products of this neutral chemistry are aggressive responses that are distinctively human… Territoriality is one of the variants of aggressive behavior that can be directly evaluated by the new insights of biology. Students of animal behavior define a territory as an area occupied more or less exclusively either directly by overt defense or indirectly through advertisement. This area invariably contains a scarce resource, usually a steady food supply, shelter, space for sexual display, or a site for laying eggs…

Close studies by zoologists of the daily schedules, feeding’ behavior, and energy expenditures of individual animals have revealed that territorial behavior evolves in animal species only when the vital resource is economically defensible: the energy saved and the increase in survival and reproduction due to territorial defense outweigh the energy expended and the risk of injury and death. The researchers have been able to go further in some instances to prove that in the case of food territories the size of the defended area is at or just above the size required to yield enough food to keep the resident healthy and able to reproduce. Finally, territories contain an “invincible center.” The resident animal defends the territory far more vigorously than intruders attempt to usurp it, and as a result the defender usually wins. In a special sense, it has the “moral advantage” over trespassers.

The study of territorial behavior in human beings is in a very early stage. We know that bands of hunter-gatherers around the world are commonly aggressive in their defense of land that contains a reliable food resource…

Areas defended by hunter-gatherers are precisely those that appear to be the most economically defensible. When food resources are scattered in space and unpredictable in time, the bands do not defend their home ranges and in fact often share occasional discoveries of rich food sources. The Western Shoshoni, for example, occupied an arid portion of the Great Basin in which the amount of game and most plant foods was poor and unpredictable. Their population density was very low, about one person in twenty square miles, and hunting and foraging were usually conducted by solitary individuals or families. Their home ranges were correspondingly huge, and they were forced into a nomadic existence. Families shared information on good pinon crops, concentrations of locusts, and forthcoming rabbit drives. Western Shoshoni seldom aggregated long enough to form bands or villages. They had no concept of ownership of land or any resource on it, with the single exception of eagle nests.

In contrast, the Owens Valley Paiute occupied relatively fertile land with denser stands of pinon pine and abundant game. Groups of villages were organized into bands, each of which owned sections of the valley that cut across the Owens River and extended up the mountains on either side. These territories were defended by means of social and religious sanctions reinforced with occasional threats and attacks. At most, the residents invited members of other bands, especially their relatives, to pick pinon nuts on their land.

The flexibility displayed by the Great Basin tribes parallels that occurring among other populations and species of mammals. In both men and animals its expression is correlated with the richness and spatial distribution of the most vital resources within the home range…

The biological formula of territorialism translates easily into the rituals of modern property ownership. When described by means of generalization clear of emotion and fictive embellishment this behavior acquires new flavor— at once intimately familiar, because our own daily lives are controlled by it, and yet distinctive and even very peculiar, because it is after all a diagnostic trait of just one mammalian species. Each culture develops its own particular rules to safeguard personal property and space.

Pierre van den Berghe, a sociologist, has provided the following description of present-day behavioraround vacation residents near Seattle:

Before entering familial territory, guests and visitors, especially if they are unexpected, regularly go through a ritual of identification, attention drawing, greeting and apology for the possible disturbance. This behavioral exchange takes place and is preferably directed at adults. Children of the owners, if encountered first, are asked about the whereabouts of their parents. When no adult owners are met outdoors, the visitor typically goes to the dwelling door, where he makes an identifying noise, either by knocking on the door or ringing a bell if the door is closed, or by voice if the door is open. The threshold is typically crossed only on recognition and invitation by the owner. Even then, the guest feels free to enter only the sitting room, and usually makes additional requests to enter other parts of the house, such as a bathroom or bedroom.

When a visitor is present, he is treated by the other members of the [vacation residence] club as an extension of his host. That is, his limited privileges of territorial occupancy extend only to the territory of his host, and the host will be held responsible by other owners for any territorial transgressions of the guests ... Children, too, are not treated as independent agents, but as extensions of their parents or of the adult “responsible” for them, and territorial transgressions of children, especially if repeated, are taken up with the parents or guardians…

War can be defined as the violent rupture of the intricate and powerful fabric of the territorial taboos observed by social groups. The force behind most warlike policies is ethnocentrism, the irrationally exaggerated allegiance of individuals to their kin and fellow tribesmen. In general, primitive men divide the world into two tangible parts, the near environment of homes, local villages, kin, friends, tame animals, and witches, and the more distant universe of neighboring villages, intertribal allies, enemies, wild animals, and ghosts. This elemental topography makes easier the distinction between enemies who can be attacked and killed and friends who cannot. The contrast is heightened by reducing enemies to frightful and even subhuman status…

The proneness toward violent aggression is a good example that cultural practices are directed to some extent by genetic traits favoring entire groups while disfavoring the individual members that display them...

The particular forms of organized violence are not inherited. No genes differentiate the practice of platform torture from pole and stake torture, headhunting from cannibalism, the duel of champions from genocide. Instead there is an innate predisposition to manufacture the cultural apparatus of aggression, in a way that separates the conscious mind from the raw biological processes that the genes encode. Culture gives a particular form to the aggression and sanctifies the uniformity of its practice by all members of the tribe.

The cultural evolution of aggression appears to be guided jointly by the following three forces: (1) genetic predisposition toward learning some form of communal aggression; (2) the necessities imposed by the environment in which the society finds itself; and (3) the previous history of the group, which biases it toward the adoption of one cultural innovation as opposed to another.

To return to the more general metaphor used in developmental biology, the society undergoing cultural evolution can be said to be moving down the slope of a very long developmental landscape. The channels of formalized aggression are deep; culture is likely to turn into one or the other but not to avoid them completely. These channels are shaped by interaction between the genetic predisposition to learn aggressive responses and the physical properties of the home range that favor particular forms of the responses. Society is influenced to take a particular direction by idiosyncratic features of its preexisting culture…

Although the evidence suggests that the biological nature of humankind launched the evolution of organized aggression and roughly directed its early history across many societies, the eventual outcome of that evolution will be determined by cultural processes brought increasingly under the control of rational thought. The practice of war is a straightforward example of a hypertrophied biological predisposition. Primitive men cleaved their universe into friends and enemies and responded with quick, deep emotion to even the mildest threats emanating from outside the arbitrary boundary. With the rise of chiefdoms and states, this tendency became institutionalized, war was adopted as an instrument of policy of some of the new societies, and those that employed it best became— tragically—the most successful. The evolution of warfare was an autocatalytic reaction that could not be halted by any people, because to attempt to reverse the process unilaterally was to fall victim. A new mode of natural selection was operating at the level of entire societies…

Keith Otterbein, an anthropologist, has studied quantitatively the variables affecting warlike behavior in forty-six cultures, from the relatively unsophisticated Tiwi and Jivaro to more advanced societies such as the Egyptians, Aztecs, Hawaiians, and Japanese. His main conclusions will cause no great surprise: as societies become centralized and complex, they develop more sophisticated military organizations and techniques of battle, and the greater their military sophistication, the more likely they are to expand their territories and to displace competing cultures.

Civilizations have been propelled by the reciprocating thrusts of cultural evolution and organized violence, and in our time they have come to within one step of nuclear annihilation. Yet when countries have reached the brink, in the Formosan Straits, Cuba, and the Middle East, their leaders have proved able to turn back. In Abba Eban’s memorable words on the occasion of the 1967 Arab-Israeli war, men use reason as a last resort…

To recapitulate the total argument, human aggression cannot be explained as either a dark-angelic flaw or a bestial instinct. Nor is it the pathological symptom of upbringing in a cruel environment. Human beings are strongly predisposed to respond with unreasoning hatred to external threats and to escalate their hostility sufficiently to overwhelm the source of the threat by a respectably wide margin of safety.

Our brains do appear to be programmed to the following extent: we are inclined to partition other people into friends and aliens, in the same sense that birds are inclined to learn territorial songs and to navigate by the polar constellations. We tend to fear deeply the actions of strangers and to solve conflict by aggression. These learning rules are most likely to have evolved during the past hundreds of thousands of years of human evolution and, thus, to have conferred a biological advantage on those who conformed to them with the greatest fidelity.

The learning rules of violent aggression are largely obsolete. We are no longer hunter-gatherers who settle disputes with spears, arrows, and stone axes. But to acknowledge the obsolescence of the rules is not to banish them. We can only work our way around them. To let them rest latent and unsummoned, we must consciously undertake those difficult and rarely traveled pathways in psychological development that lead to mastery over and reduction of the profound human tendency to learn violence…

With pacifism as a goal, scholars and political leaders will find it useful to deepen studies in anthropology and social psychology, and to express this technical knowledge openly as part of political science and daily diplomatic procedure. To provide a more durable foundation for peace, political and cultural ties can be promoted that create a confusion of cross-binding loyalties… If the tangle is spun still more thickly, it will become discouragingly difficult for future populations to regard each other as completely discrete on the basis of congruent distinctions in race, language, nationhood, religion, ideology, and economic interest. Undoubtedly there exist other techniques by which this aspect of human nature can be gently hobbled in the interest of human welfare.