Humans Aren’t ‘Killer Apes’

All mammals are reluctant to kill each other

Most of us have probably bought into the folk saying which originated in Victorian times that nature is "red in tooth and claw,” meaning that animals are completely unsentimental, engaged in indiscriminate killing at will. From there, it’s often extrapolated that humans are really no different from our non-human animal cousins. But as with so many of our cultural narratives, what’s widely believed has little basis in science or fact.

Although aggression does serve a variety of evolutionary functions, varying some from species to species, in general (just as with any behavior) it is designed to maximize benefits and minimize costs to fitness. What we see when we look at the actual data is that except in very particular exceptions, most animals exert a lot of restraint when sparring with others of their species. They don’t actually want to kill them most of the time, and may even engage in reconciliatory behaviors after a fight. This applies to both human and non-human animals.

A while back I wrote Peaceful Humanity or Not? which was in turn an extended response to Large Scale Violence Only Began With the Agricultural Revolution that I then made into a story. Although I stand firmly behind both of those pieces and think that they are well supported with data and citations, it’s always nice to have a few more. I recently started reading War, Peace, and Human Nature which is thus described, “In this book, editor Douglas P. Fry brings together leading experts in evolutionary biology, archaeology, anthropology, and primatology to find answers to fundamental questions about peace, conflict, and human nature in an evolutionary context.

Douglas Fry is an American anthropologist who has written extensively on aggression, conflict, and conflict resolution. The cadre of writers who contributed to this book are all scholars in their fields, writing in an academic style. The version that I bought is actually a textbook, so each of the 27 chapters has several pages of citations and although it’s a bit dense in places, I’ve really learned a lot from it.

The overwhelming takeaway that I got was that most animals, particularly mammals, including ones who are considered to be highly aggressive such as chimpanzees, only kill each other under very specific conditions. In general, unless they can be virtually assured of doing so at very low risk to themselves, both human and non-human animals are much more likely to engage in alternatives to violence. Both have extensive conflict avoidance techniques as well as reconciliation habits.

In the chapter called Why the Legend of the Killer Ape Never Dies Robert W. Sussman points out, “By 2004, there had been only 17 suspected and 12 “observed” cases of adult chimpanzee-chimpanzee killings reported from four of nine chimpanzee long-term research sites. This spanned a total of 215 years of combined observer time at these sites and yields a maximum rate of one chimpanzee killing every 7.5 years.” (p. 104)

Thus, social animals appear to be wired to cooperate and to reduce stress by seeking each other’s company.

He goes on to say, “I am not claiming that chimpanzees and humans are not violent under certain circumstances, as we all know they are, but that the claims of inherent “demonism” in both chimpanzees and humans are erroneous. Furthermore, research indicates that the neurophysiology of aggression between species (that is, predation) is quite different from spontaneous violence linked to intraspecific aggression by humans (that is murder).” (p. 104)

“De Waal (2006) contends that chimp societies emphasize reconciliation and consolation after conflict; his 40 years of primate behavior observations have documented that concern for others is just natural conduct for our closest primate relatives. Thus, social animals appear to be wired to cooperate and to reduce stress by seeking each other’s company. If cooperation and physical proximity among group-living animals are rewarding in a variety of environmental and social circumstances and if physiological and neurological feedback systems reinforce social tolerance and cooperative behavior, then social living can persist in the absence of any conscious recognition that material gains might also flow from mutual cooperation. Based on the latest research, friendly and cooperative behaviors provide psychological, physiological, and ecological benefits.” (p. 107)

In most cases, unless one group of chimps is vastly bigger and stronger than another, they never even get close to each other in the wild, but instead will pant-hoot at each other from afar. In fact, chimps rarely patrol the edges of their territory, preferring to keep more to the center, where they are less likely to encounter strangers. As is noted in Chimpanzees, Warfare, and the Invention of Peace, a chapter written by Michael L. Wilson, “Because aggression generally involves costs, animals usually avoid getting into direct fights if they can (Fry & Szala, chapter 23). Instead, they threaten and display at their rivals. If they do get into a direct fight, animals usually seem content to chase rivals off rather than pursuing, capturing, and killing them. Fatal fights may occur, however, when the value of the resource is particularly high, or when the fighters do not expect to live long, or when the cost of killing their opponent is low.” (p. 363)

As Sussman pointed out above, there are psychological, physiological and ecological benefits to cooperation and pro-social behavior as well.

So, one might suggest that refraining from violence is not about altruism, but about cost-benefit analysis. To some extent, this is true, but it is only one factor among many. Male lions who kill cubs so that they can mate with the females and eliminate genetic competitors have a high cost-benefit ratio in doing so. They have much to gain and little to lose. But more generally, most animals do not try to kill each other and concentrate more often on shows of prowess and strength where one combatant will eventually acquiesce without much harm being done to either. Many animals seem to follow rules about primarily engaging with each other in ways where serious damage is unlikely to be done. Most primates only bite each other on heavily furred regions, for example. Horned animals try not to gouge each other, although they are not always successful. As Sussman pointed out above, there are psychological, physiological, and ecological benefits to cooperation and pro-social behavior as well.

Chapter 23, The Evolution of Agonism noted, “As we shall see, unrestrained aggression (the last category in Figure 23.1) is exceedingly rare among mammals. An important implication of this fact is that any claim that escalated, unrestrained fighting is species-typical in humans must be strongly justified, rather than simply assumed a priori, as such a claim flies in the face of a well-documented mammalian pattern of restrained agonism. The burden of scientific proof reasonably rests with any claimants that human agonism (the benefits of conflict) in this regard constitutes an exception to a widespread mammalian pattern. The logical default proposition would be that human aggression rather opposes than constitutes a reversal of selection pressures to favor homicide or war.” (p. 455)

Particularly for very social species, such as primates, the pro-social aspects of non-lethal behavior are also a factor as well as the cost-benefit analysis of probable victory for engaging in it. To say that humans are inherently warlike or inherently peaceful is to oversimplify. However, there is significant evidence that even cultures that are considered to be quite violent still have mechanisms for avoiding lethal interactions. Sometimes those involve simply avoiding each other and sometimes they are more elaborate, including singing contests or ritualized battles where conflicts may be resolved without any significant bloodshed. Periods of peace may be agreed upon to allow for trade as well.

The idea of humans as killer apes was rather curious given how little pleasure we take in lethal combat.

We know that killing is difficult for most humans, in that they have to be indoctrinated into it in order to become effective soldiers, and even then, there are countless stories of the ways that even soldiers in wartime do things to avoid killing. “The majority of soldiers, although well-armed, never kills. During World War II, only one out of every five American soldiers actually fired at the enemy. Similarly, it has been calculated that during the Vietnam War, American soldiers fired over 50,000 bullets for every enemy soldier killed. Most bullets ended up in the air.”

As Frans de Waal further says in the forward of the book:

The idea of humans as killer apes was rather curious given how little pleasure we take in lethal combat. Species-typical tendencies normally include built-in rewards. Nature has ensured that we find fulfillment in eating, sex, and nursing, all of which are required for survival and reproduction. If warfare were truly in our DNA, we should happily engage in it. Yet, soldiers report a deep revulsion to killing, and only shoot at the enemy under pressure. They end up with haunting memories. Far from being a recent phenomenon, combat trauma was already known to the ancient Greeks, such as Sophocles, who described the “divine madness” now known as Post Traumatic Stress Disorder (PTSD). A most illuminating book in this regard is On Killing by Dave Grossman

The great difference in levels of violence between various human societies speaks to the importance of culture in determining how much killing actually does take place. But even then, deaths are calculated by the number per every 100,000 people. Even during times of war, killing is generally not as widespread as our perception of it is. In WWII, less than 1% of fighter pilots shot down 30–40% of enemy planes, and the vast majority of pilots did not shoot down any. (p.466)

In addition, peace is not just the absence of war or violence, but should also be recognized as a complex set of mores, practices, and institutions that seek to mitigate and resolve conflict before it takes place or becomes deadly. Some have claimed that anthropologists like Fry are doves who have sought to pacify history, but the actual evidence shows that more accurately some people have sought to warrify it, disregarding all the ways that despite a capacity for killing under certain circumstances, most mammals, including humans, do it rarely and reluctantly.

As De Waal further explains, “I am not trying to ignore the role of aggression and competition in understanding primate and human social interactions. My perspective, however, is that affiliation, cooperation, and social tolerance associated with long-term mutual benefits form the core of social group living.” (p. 108).

When group stability is important for individual advantage, selection will favor active peacemaking and cooperation in our closest relatives and ourselves.

Besides the fact that up until a few thousand years ago our ancestors lived in small nomadic forager groups with a lot of kin in neighboring bands, the socially and economically cooperative nature of those cultures does not tolerate infighting or disharmony except in very limited responses to recognized breaches of the social contract of the group. It is really only with sedentism related to the agricultural revolution that these egalitarian and largely peaceful cultures began to change in favor of greater hierarchy, oppression, and scarcity which drove aggression and widespread killing. For more about that, read here.

“Destabilization of the social resource network decreases group stability and efficiency and lowers the average fitness benefit derived from cooperation. When group stability is important for individual advantage, selection will favor active peacemaking and cooperation in our closest relatives and ourselves.” (p. 401)

Humans aren’t “killer apes.” Even chimpanzees don’t deserve that title, and other mammals make significant efforts to avoid killing each other except in a few rare circumstances. Lions, who are often touted as evidence of inherent animal violence because they kill cubs fathered by other males will go out of their way to avoid interacting with members of other prides to prevent violent altercations. Among northern elephant seals, threats outnumber physical confrontations by about sixty to one. The statistics around other types of mammals of all sorts are similar. (p. 454)

The warrification of human history is simply a domination-based social system justifying and normalizing itself. Trying to use the animal kingdom as evidence that we too are red in tooth and claw in our most natural state is nothing more than a dystopian fairytale, unsupported by the actual facts. Sorry Mr. Hobbes, but just because the culture you lived in was rife with lives that were nasty, brutish, and short doesn’t mean that generalizes to human history as a whole.

All quotes are from the book War, Peace, and Human Nature, with which I have no affiliation or financial agreement.

© Copyright Elle Beau 2021 Elle Beau writes on Medium about sex, life, relationships, society, anthropology, spirituality, and love.