Revenge as a Motive for War
Research by a UMaine anthropologist finds eye-for-an-eye killing is strictly human and off the usual evolutionary path

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Today, our means of killing one another
are more sophisticated than ever, but the reasons we fight are pretty rudimentary. Humans have thermonuclear technology, but still only possess Stone Age brains — a potentially lethal combination, according to University of Maine anthropologist Paul Roscoe.

For more than two decades, Roscoe has studied revenge as a motive for war among tribes in New Guinea. His research shows that lethal revenge most frequently fuels more death than it deters, to the point that killing enemies to avenge the death of kin — something only humans do — is probably not a useful evolutionary adaptation, says the professor of anthropology and cooperating professor of Quaternary and climate studies at UMaine.

By engaging in revenge killings and warfare, humans have strayed rather far off the evolutionary path followed by most other species. The technical ability of humans to harm one another has outpaced the social and cultural abilities needed to deal with this unwise behavior, Roscoe surmises. Only in the last 10,000 years of human existence have people evolved from hunters and gatherers with spears to glorified hunters and gatherers with thermonuclear weapons.

"We may have thermonuclear technology, but we still have Stone Age brains," Roscoe says. "Our social and political systems are slow to adapt in comparison to the pace of technological development. To make matters worse, even when we sometimes manage to catch up, technology has by then advanced further and the goalposts have shifted."

Evolutionarily speaking, it does not make sense to engage in behavior that may not only kill you, but also members of your clan or tribe. Writ large in a nuclear exchange, revenge killing could theoretically wipe out your entire species. It makes evolutionary sense to fight and then back off, says Roscoe.

For example, male red deer competing for territory or mates first roar at one another. If neither backs away, the animals then pace side by side, sizing up each other. If this fails to resolve the conflict, the two animals may fight, but the results are typically not lethal.

Previous theories on motives for revenge focused on an escalating tit-for-tat complex, in which humans simply take behavior routinely practiced by other animals to the next step. Many animal species engage in escalating aggressive behavior. Humans are the only animals to seek out enemies and kill them for past actions.

Taking a different approach, Roscoe argues that this is because humans have a large, highly developed neocortex, the region of the brain responsible for intellectual thought and creativity. The neocortex is believed to have evolved for positive purposes, such as enabling humans to develop tools, communicate through language, and plan cooperative hunting trips. But history shows it has not always been used for positive pursuits, says Roscoe, who presented his theory and research earlier this year at the prestigious annual meeting of the American Association for the Advancement of Science in Denver, Colo.

"Humans developed the ability to model actions before they happen. This means we can plan collective violence. It explains why we have warfare," he says. Research on chimps confirms that, once you can gang up and launch a surprise attack on outnumbered victims, killing becomes a dramatically more attractive option than it is in the one-on-one confrontations typical of other species.

The development of human intelligence gives our species greater ability to use violence and killing as a tool to achieve various ends — to further an ideology, eradicate an ethnic group, keep borders secure. Humans also use their intellect to develop sophisticated weapons that make killing more efficient while avoiding face-to-face conflict, thereby circumventing our inbred aversion to killing others of our species.

The neocortex also allows humans to manipulate their emotional states and dehumanize enemies for the same purpose. For instance, warriors can whip themselves into an angered frenzy by recalling slain kin and engaging in repetitive, militaristic chants. Many tribes in New Guinea refer to their enemies as "our game," and world leaders have equated their enemies to mad dogs and rats.

Roscoe's research focuses on the little-studied wars waged by tribes in New Guinea, many of which did not have contact with outsiders until the 1930s. The island presents a potential treasure trove of information on warfare because, at the time of contact, there were thousands of groups that spoke more than 1,000 languages. They often were at war with one another until well into the 20th century.

Roscoe first lived among the Yangoru Boiken people for a year and a half in the early 1980s and has returned there three times. His early research was on the need for family planning among the people living in the foothills of a coastal mountain range in the north of the South Pacific island. While there, he also did general ethnographic studies, which informed his current work.

Like early white visitors to the island, Roscoe was viewed as a spirit of the dead. Locals thought he was a reincarnated ancestor, a responsibility Roscoe did not take lightly. He provided anti-malarial drugs and other medical assistance to residents and, in exchange, had a window on their world.

The Yangoru Boiken use sorcery to explain many events, including illness and crop failures. Sorcery also played a role in the island's warfare; clans fought to avenge deaths caused by spells.

"I had the gut recognition that we would do the same thing if we were in their circumstances. New Guineans are the same as us; they just don't have the complex technology and political structure that we have," Roscoe says.

Major tribal warfare in New Guinea ended nearly six decades ago, so in recent years, Roscoe has traveled to archives around the world to collect data about warfare in contact-era New Guinea. Roscoe studied the writings of missionaries and explorers, many of them German and Dutch, who visited the South Pacific island before most anthropologists arrived.

He found that much of the warfare in New Guinea was, in fact, precipitated by revenge; the motive was to weaken the enemy and forestall further aggression. Some tribes believed they must fight until there was an equal number of dead on both sides. Others believed they must inflict lethal revenge to be spared attacks from the ghosts of clansmen killed in prior conflicts. Fighting often escalated, sometimes involving groups not party to the initial clash, and continued for generations.

"My hope is that somewhere down the road, we will use this knowledge to get around killing one another. We need to figure out why we have war before it wipes us off the planet," Roscoe says.

by Susan Young
May-June, 2003

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