As of January 2018, the symbolic Doomsday Clock reads two minutes to midnight. The current age of global instability and uncertainty has revived discussion of an age-old question: is war ingrained in human nature? Warfare has been studied for centuries, by everyone from historians of ancient Greece to primatologists. But something strange is happening to the way we consider the subject, especially with respect to the study of chimp-on-chimp violence. Conspecific killing among chimpanzees (i.e. when chimps kill one another) has become a particularly political and controversial topic, and contending arguments seem to reflect the ideological preferences and outlook of the researchers on either side of the debate. At issue are the implications data about primate warfare might have for our understanding of human violence.

A link between chimpanzee and human warfare has been stated outright by leading primatologists, who suggest that it demonstrates humans’ innate predisposition for violence. I first encountered this controversy during graduate school. Steven Pinker had just published The Better Angels of Our Nature which provoked heated discussion of war-like behavior as an evolutionary mechanism in humans. Then, two years later, as I was beginning my PhD investigating soldiers’ experiences of killing in combat, Douglas Fry edited a book entitled War, Peace, and Human Nature, which brought forward a plethora of researchers from a range of disciplines to argue that war is in fact neither an innate nor an ancient part of human civilization.¹ This new research critiqued popularized theories that warfare is as ancient as humans themselves, and the debate entered popular public discourse with articles appearing in Nature² and on the New Scientist blog, and a flurry of arguments ensued about the dangers of embracing the idea that humans and chimps are built for war.

Chimp warfare had been studied for decades. A 2010 study of Ngogo chimps best summarizes the controversies in the field.³ Over a ten-year period, researchers observed a band of Ngogo chimpanzees as it systematically annihilated a neighbouring faction. The chimps did not simply wipe their rivals out; they formed patrols which could attack and kill any weaker force they encountered, and the dominant faction continued killing until it succeeded in annexing all of the opposing tribe’s territory. Was this simply an unusually violent group of chimps? Separate studies suggest not. Detailed observations of intergroup killing have been reported from multiple chimp study sites including the Budongo and the Gombe, with some research suggesting it is likely that as many as 30 percent of chimpanzees are killed during wars among males.^{1, 4}

It might be argued that the animals’ motivation for coalitional killing is simply the acquisition of more resources (perhaps due to food shortages), that it is too dangerous to remain in close proximity to another faction, or that the potential mating options are too tempting to remain at peace with a neighboring tribe. However, researchers have reported occurrences of coalitional killing when there was minimal risk to the attackers, or when resources were demonstrably not a primary motive.⁴ Michael Wilson, an eminent primatologist in the field of coalitional killing, has observed that there are times when dominant male chimps attack others without a clear motive,¹ and engage in bullying behavior.

Typically, this behavior has been explained by Harvard primatologist Richard Wrangham’s ‘imbalance of power’ hypothesis,⁵ which holds that selection favors a tendency to hunt and kill rivals when the costs are sufficiently low (i.e. when one party can attack another with impunity). Wrangham noted that the long-term benefits of violent incursions by chimps into each other’s territory are opaque to the animals involved. His observations of chimpanzees during tribal skirmishes persuaded him that there must therefore be a biological or innate component driving the behavior. Chimps send out patrols to hunt and kill an enemy when the odds are in their favor and for no obvious immediate gain. Absent obvious competition for resources, this means that if and when there is a shortage, the killing group will have more males during the inevitable group confrontations.⁶ Add camouflage and an assault rifle, and it becomes obvious why some people find these theories unsettling. The similarities to human behavior of domination for long term gain are unnerving.

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Despite the collection of abundant evidence in support of this theory, John Horgan (author of The End of War) and Brian Ferguson, both adamant critics of Wrangham, suggest that the popularity of his imbalance of power hypothesis has more to do with the militarism of American culture than with any scientific merit. Horgan even suggests that Wrangham’s thinking makes it easy to abdicate our responsibility to end war by simply blaming it on human nature. Others have suggested that chimp warfare is not innate at all, and that it is shaped by humans’ environmental interference in the form of deforestation and logging, which forces chimps into closer proximity and thus competition for resources. In response to this latter claim, Wilson collaborated with 30 other primatologists to conduct an analysis of 152 killings in 18 chimpanzee communities.² The researchers found evidence supporting adaptive strategies for coalitional killing (increased access to resources and attackers outnumbering the victims) but no evidence to support the theory that chimp violence was caused by human impact on the environment.

Refusing to concede the point, Horgan has countered that Wilson and colleagues only directly observed 15 killings – an average of one killing every 28 years in a typical community. Horgan argues that, in observational studies of coalitional killing among chimpanzees conducted since the 1960s, many of these killings have been ‘suspected’ or ‘inferred’ rather than directly observed. In a further attempt to distance humans (and chimps) from any notion of innate war-like behavior, the argument has shifted from chimps actually engaging in conspecific killing for motivations unrelated to immediate needs, to environmental factors and methodological criticisms.

The debate rages on and it is unlikely to end any time soon. This is not because humans and chimps, respectively, don’t wipe each other out (they obviously do), but because Wilson’s critics fear the implications of his hypothesis: that humans are killer chimps, with the addition of an overactive frontal lobe and a pair of opposable thumbs. Researchers have already suggested that we are natural born killers, and that, in all likelihood, we inherited these violent patterns of behavior from a common ancestor.

With the existence of apocalyptic weaponry that could cause an extinction event, the question of whether or not warfare is part of our genetic makeup will, invariably, come up the next time Donald Trump and Kim Jong Un exchange heated rhetoric, or another North Korean missile is launched into the Sea of Japan. Acknowledging the inescapable conclusion that humans are innately violent, brings us to the crux of the issue.

The critics of Wilson et al are committing a common naturalistic fallacy by conflating an acknowledgment of innate violence with its endorsement. More irresponsibly, they rest our responsibility for preventing war on the notion that violence is not innate when copious data suggests that it is. Most worrying of all is that Wilson’s critics are basing their understanding of reality on what they find desirable, and rejecting claims that they find undesirable. Since objective reality is indifferent to human ideological preference, this is a highly unreliable way of conducting scientific inquiry.

It is unwise to rest moral and ethical claims on descriptions of reality that may subsequently be disproven. It is also unnecessary. As Steven Pinker remarked at the end of the chapter on violence in his 2002 book, The Blank Slate:

Many intellectuals have averted their gaze from evolutionary logic of violence, fearing that acknowledging it is tantamount to accepting it or even approving of it. Instead they have pursued the comforting delusion of the Noble Savage, in which violence is an arbitrary product of learning or a pathogen that bores into us from the outside. But denying the logic of violence makes it easy to forget how readily violence can flare up, and ignoring the parts of the mind that ignite violence makes it easy to overlook the parts that can extinguish it. With violence, as with so many concerns, human nature is the problem, but human nature is also the solution.⁷

As Pinker contends, there has been a steady decline of violence across the globe. This is due in part to our ability to inhibit the worst aspects of ourselves, so that we can function and co-operate as a society. We do this by expressing our peaceable inclinations. We have created laws and systems of justice to tackle cyclical violence and revenge killings. And we have formed alliances based on trade and protection, reciprocal positive-sum arrangements that prevent needless deaths from invasions and plunder. It is precisely by acknowledging the darkest parts of ourselves and taming them that we have learned to work in our mutual self-interest to create societies free from the everyday fear of death by war.

References:

¹ FRY, D.P., 2013. War, Peace, and Human Nature: The Convergence of Evolutionary and Cultural Views. Oxford: Oxford University Press.
² WILSON, M.L., et al., 2014. Lethal Aggression in Pan Is Better Explained by Adaptive Strategies than Human Impacts. Nature, 513(7518), pp.414-417. 
³ MITANI, J.C., WATTS, D.P. & AMSLER, S.J., 2010. Lethal Intergroup Aggression Leads to Territorial Expansion in Wild Chimpanzees. Current Biology, 20(12), pp. 507-508. 
⁴ DYER, G. 2004. War: The New Edition. Canada: Random House Canada.
⁵ WRANGHAM, R.W., 1999. Evolution of Coalitionary Killing. Yearbook of Physical Anthropology, 29, pp.1–30.
⁶ WRANGHAM, R. W., 2006. Why Apes and Humans Kill. In Conflict, Martha Jones and A.C. Fabian, eds., pp.43-62. New York, NY: Cambridge University Press. S
⁷ PINKER, S. 2003. The Blank Slate: The Modern Denial of Human Nature. London: Penguin Books. Page 336.