November 12, 2008

Scientists Examine Evolutionary Origins Of War

Despite enormous costs and often-tragic results, humans have waged war throughout the course of history, and continue to do so today. 

The report cites an emerging theory that challenges conventional wisdom that war is a relatively recent phenomenon based on conflicting human cultures.  The new theory, which represents the first time archaeologists, anthropologists, primatologists, psychologists and political scientists have approached a consensus on the matter, holds that war is as ancient as humankind and has played a crucial role in human evolution.  

The theory even helps explain the evolution of some well-known aspects of warlike behavior, including gang warfare, and suggests that some of the cooperative skills we developed to become successful warriors have morphed into modern abilities to work together towards a common goal.

These are some of the themes that emerged at a conference at the University of Oregon last month on the evolutionary origins of war.

"The picture that was painted was quite consistent," Mark Van Vugt, an evolutionary psychologist at Britain's University of Kent, told New Scientist.

"Warfare has been with us for at least several tens, if not hundreds, of thousands of years."

Indeed, Van Vugt believes the propensity towards warfare existed in the common ancestor we share with chimps.

"It has been a significant selection pressure on the human species," he said, adding that fossils of some early humans have wounds consistent with warfare.

Research indicates that warfare accounts for at least 10 per cent of all male deaths in present-day hunter-gatherers.

"That's enough to get your attention," said Stephen LeBlanc, an archaeologist at Harvard University's Peabody Museum in Boston.

Primatologists have long known that organized, deadly violence is common between groups of chimpanzees, our closest relatives. Whether between chimps or hunter-gatherers, however, intergroup violence is distinctly different from modern pitched battles.  Instead, it typically takes the form of brief raids of overwhelming force,  in order to limit risk of injury among the aggressors 

"It's not like the Somme," Richard Wrangham, a primatologist at Harvard University, told New Scientist.

"You go off, you make a hit, you come back again."

This opportunistic brutality helps the aggressors weaken their enemies,  thus increasing their territorial holdings.

Wrangham said such raids are possible because, unlike most social mammals, chimps and humans often stray from the main group to forage singly or in smaller groups. 

Bonobos, another close relative to humans, have little or no intergroup violence because they typically live in habitats where food is easier to obtain, precluding the need to stray from the group.

If group violence has existed throughout history in human society then it is logical to conclude we have evolved psychological adaptations to a warlike lifestyle. 

Several conference participants presented the strongest evidence to date that males have evolved a tendency towards aggression outside the group but cooperation within it.

"There is something ineluctably male about coalitional aggression - men bonding with men to engage in aggression against other men," says Rose McDermott, a political scientist at Stanford University in California.

The larger and more muscular bodies of men make them better suited for fighting.  In contrast, aggression in women is usually in the form of verbal rather than physical violence, and is primarily one on one, McDermott said.

And while gang instincts may have evolved in women, it is to a much lesser extent, according to evolutionary psychologist John Tooby at the University of California at Santa Barbara.

This is partly attributable to our evolutionary history, in which men are typically stronger than women and therefore better suited for physical violence.  This could also explain why female gangs only tend to form primarily in same-sex environments such as prison or high school.  Additionally, women have more to lose from aggression since they bear the brunt of child-rearing.

As might be expected, McDermott, Van Vugt and their colleagues found that men are more aggressive than women in role playing games in which each plays the leader of a fictitious country. 

However, Van Vugt's team found more muted effects in group bonding.  For instance, male undergraduates were more likely than women to donate money towards a group effort, but only when competing against rival universities.  If told instead that the goal was to test their individual responses to group cooperation, the men contributed less cash than the women.

The bottom line was that men cooperated only in the context of intergroup competition.  

While some of this behavior might be attributed to conscious mental strategies, anthropologist Mark Flinn of the University of Missouri found that group-oriented responses also occur on the hormonal level.

Flinn told the conference that cricket players on the island of Dominica experience a testosterone spike after winning against a rival village.  However, this hormonal surge, and presumably the dominant behavior it elicits, was not observed when the men beat a team from their own village.

"You're sort of sending the signal that it's play. You're not asserting dominance over them," he said.

Likewise, the testosterone surge a man often experiences when in the presence of a potential mate is lessened if the woman is in a relationship with his friend.  Again, the effect is to diminish competition within the group, explains Flinn.

"We really are different from chimpanzees in our relative amount of respect for other males' mating relationships."

The ultimate effect of all this is that groups of men take on their own special dynamic such as that seen among soldiers in a platoon, or football fans out on the town.  These groups have confidence, cohesion, and are often aggressive, precisely the traits a group of warriors requires.

Wrangham said that chimpanzees don't go to war in the same way as humans because they lack the abstract thought necessary to view themselves as part of a collective beyond their immediate associates.

"The real story of our evolutionary past is not simply that warfare drove the evolution of social behavior," Samuel Bowles, an economist at the Santa Fe Institute and the University of Siena, told New Scientist.

Instead, the real driver was "some interplay between warfare and the alternative benefits of peace," he said. 

Although women seem to negotiate harmony within groups, men may be better at peacekeeping between groups, said Van Vugt.

Tooby said our history of warfare may have given humans additional benefits as well.

"The interesting thing about war is we're focused on the harm it does," he said.

"But it requires a super-high level of cooperation."

And that part of our heritage is something well worth maintaining.

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