SALT LAKE CITY—As deep as scientists peer into human history and prehistory, they have found evidence of violence. That was the bad news from 17 researchers in anthropology and other fields at “The Evolution of Human Aggression: Lessons for Today’s Conflicts” conference, held at the University of Utah at the end of February. The good news is that much can be done to reduce lethal conflict in the world today. As participant Frans B. M. de Waal of Emory University put it, humans are not “destined to wage war forever.”
De Waal, who studies primates, noted that observations of lethal group encounters among chimpanzees, our closest genetic relatives, have promulgated the fatalistic belief that “war is in our DNA.” But chimps are also “peacemakers,” de Waal pointed out; they reconcile after fights by hugging, mouth and hand kissing, mutual grooming and food sharing. Humans engage in such behavior, too, de Waal said, flashing a photograph of John McCain and George W. Bush embracing—albeit with hideously insincere grins—after their bitter primary contest in 2000.
Reconciliation takes place, de Waal contended, “whenever parties stand to lose if their relationship deteriorates.” Chimpanzees from different troops, which compete for territory and hence treat one another with lethal hostility, rarely if ever reconcile, he noted. Among humans, however, “interdependencies between groups or nations are not unusual.” To promote peace, he suggested, nations should foster economic interdependence through alliances such as the European Union. Although the E.U. has “not created love between Germany and France” and other former adversaries, de Waal acknowledged, it has greatly reduced the likelihood of war in Europe.
Harvard University anthropologist Richard Wrangham agreed with de Waal that primate violence is not compulsive, or “instinctual,” but is “extremely sensitive to context.” One of the most robust predictors of violence between two groups of primates, Wrangham proposed, is an imbalance of power. Chimps from one troop invariably attack individuals from a rival troop when the attackers have an overwhelming number advantage and hence a minimal risk of death or injury.
Although humans are much less risk-averse than chimps, Wrangham asserted, human societies—from hunter-gatherers to modern nations such as the U.S.—also behave much more aggressively toward rival groups when they are confident they can prevail. Reducing imbalances of power between nations, Wrangham said, should reduce the risk of war.
So should controlling population, according to anthropologist Polly Wiessner of the University of Utah. Wiessner is an authority on the Enga, a tribal people who raise crops and pigs in the highlands of Papua New Guinea. Warfare first surged among them 200 years ago, Wiessner said, after the introduction of sweet potatoes led to food surpluses and rapid population growth. Mortality rates subsided after Enga elders instituted stricter rules for warfare, such as bans on killing of women and mutilation.
The introduction of modern medicine into Enga society some 25 years ago decreased childhood mortality, triggering another “youth bulge” and surge in tribal conflict. Mortality rates have soared, Wiessner explained, because Engans now fight with shotguns and automatic weapons rather than clubs, knives and spears, their traditional weapons. Moreover, young mercenaries called “Rambos” hire themselves out to tribes in exchange for cash, young women and other booty. Together with promoting birth control, giving young men “a meaningful way forward in life” should decrease violence, Wiessner proposed.
Climate change has also driven conflict. This lesson emerged from Patricia Lambert’s studies of the Chumash, hunter-gatherers who inhabited the coast of southern California for millennia before the arrival of Europeans. Many Chumash skeletons display signs of violence, including skull fractures and embedded arrow or spear points. Analysis of tree rings and other evidence, said Lambert, an anthropologist at Utah State University, suggest that violence among the Chumash escalated during periods of drought.