This is the third installment in the series, Why We Fight, about the origins of warfare.
Has warfare been handed down to us through millions of years of evolution? Is it part of who we are as a species? At the heart of this question is whether humans have a natural capacity to kill other humans. Some social scientists have concluded that evolution has in fact left us with this unfortunate ability.
Primatologist Richard Wrangham, a major proponent of this idea, developed the “Imbalance of Power Hypothesis” to explain how evolution could produce a propensity for warfare in humans. The idea is that our primate ancestors could have gained access to additional food and other resources by attacking and killing their neighbors. Of course, these deadly attacks would have only been worthwhile if the attackers could ensure their own safety. So, Dr. Wrangham reasons, our ancestors would have carried out deadly attacks only when they severely outnumbered their victims. The conclusion is that our ancestors who were psychologically predisposed to cooperatively pick off their neighbors would have had a distinct evolutionary advantage. Or, in Dr. Wrangham’s words, ”there has been selection for a male psyche that, in certain circumstances, seeks opportunities to carry out low-cost attacks on unsuspecting neighbors.” This trait would have been amplified and passed down through the generations until it was eventually inherited by modern humans, who presumably took this predisposition and ran with it, inventing more and more efficient ways to kill each other.
The “Imbalance of Power Hypothesis” is largely based on evidence of violence in the animal world, particularly observations of violent behavior among chimpanzees, our closest animal relatives. But other social scientists have instead studied modern humans in an attempt to discover whether warfare is rooted in evolution. And, contrary to the predictions of the “Imbalance of Power Hypothesis,” many of these scientists have concluded that humans have an innate aversion to killing others.
Evidence of a powerful resistance to killing has popped up in unexpected places. Many people assume that soldiers in a firefight instinctively respond to enemy fire by shooting back, and that soldiers in a kill-or-be-killed situation will choose to kill. But informal interviews conducted with thousands of American combat soldiers during World War II by army historian S.L.A. Marshall revealed that as many as 75% of soldiers never fired their weapons during combat. In recent years the rigor of Marshall’s research methods has been called into question, but his basic conclusion that the majority of soldiers will not return fire during combat if left to their own devices has been corroborated by evidence and accounts from other wars, including the American Civil War, World War I, and the Falklands War.
So why didn’t these soldiers use their weapons? Lt. Col. Dave Grossman, a psychologist and professor of military science, looked at this evidence and concluded “that there is within most men an intense resistance to killing their fellow man. A resistance so strong that, in many circumstances, soldiers on the battlefield will die before they can overcome it.” In some ways this isn’t all that surprising. Very few people would seek out an opportunity to kill others. At the same time, you may find it hard to believe that it is sometimes impossible for soldiers to kill others even when their own lives are at risk.
And yet despite this apparent aversion to killing, we still manage to kill each other with alarming frequency. How can this be? For anthropologist Paul Roscoe the answer is that we’re simply too smart for our own good. Humans excel at overcoming our biological limitations using technological innovation: if your arms aren’t long enough to reach an apple in the upper branches of a tree, use a stick to knock it down. Can’t take the square root of large numbers in your head? Write a computer program to do it for you. Similarly, we can find ways to get around our natural aversion to killing if we decide that it’s in our best interest.
Throughout history and around the world people have come up with ways to overcome an aversion to killing, such as dehumanizing the victim, placing distance between the killer and the victim, and using drugs or loud music to induce a trance-like state in a killer. In fact, following publication of Marshall’s findings in the aftermath of World War II, the U.S. military embarked on a campaign to more effectively prepare soldiers for combat by employing realistic training exercises. New recruits began to practice shooting at pop-up, human-shaped targets rather than the traditional, stationary bull’s-eyes. More and more elaborate and realistic combat simulation exercises and ’war games’ were implemented. The point of this new training was to make killing an automatic response under combat conditions. And it worked. Interviews with American soldiers during the Vietnam War revealed that somewhere between 80 and 100 percent of soldiers shot at enemies during firefights.
Although we’ve found ways to short-circuit an aversion to killing over the years, this aversion seems deeply rooted in our minds. But where did it come from? Is it an evolved trait inherited from our distant ancestors? Or is it something that we learn and absorb from our social surroundings? Or perhaps it has emerged from an inseparable combination of both biological and cultural evolution. Regardless, this aversion to killing exists, and it reassures us that warfare is not an inescapable part of human life, and gives us hope that one day we might stop fighting wars.
ROSCOE, P. (2007). Intelligence, Coalitional Killing, and the Antecedents of War American Anthropologist, 109 (3), 485-495 DOI: 10.1525/aa.2007.109.3.485
Grossman, Dave. On Killing: The Psychological Cost of Learning to Kill in War and Society. (1995)