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
Today, our means of killing one
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
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
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,"
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
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
"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
for more stories from this issue of UMaine Today Magazine.