War: Why do we fight?

Einstein’s vision of world peace remains elusive. But the explanations he sought for why we fight are emerging, slowly, through advances in historical, social and psychological investigation.

Humans are a bipolar species. Our capacity for love, friendship and charity is unparalleled in nature. So is our capacity for cruelty, violence and warmongering. However, it would be wrong to assume that we are unique in displaying extreme aggression towards other members our species. Conflict dates back to long before the emergence of humans. It exists, to varying degrees, in all social animals.

Take the honeybee. Worker bees dedicate their lives to helping the queen, raising her brood and defending her hive to the death. Their reproductive systems are suppressed by pheromones released by the queen. For the workers, co-operating for the greater good makes evolutionary sense because the queen is the mother, or at least a half-sister, of each bee. Their genes survive through her offspring.

The moment the queen dies, however, the incentive to co-operate vanishes. In the absence of chemical suppression, the workers become fertile. Within 15 days, 5 per cent are capable of laying eggs. Within 30 days, 50 per cent are fertile. Workers become fighters, destroying each other’s eggs. The aim is to raise a son who will mate with a queen from another hive.

In bees, the trigger for conflict is chemical. In humans there is no simple biological switch but we make equivalent trade-offs between the desire for strength and solidarity in our social group — be it a band of hunter gatherers or a modern nation — and the ruthless competition for status, power and resources between group members. Ultimately, we make the same evolutionary calculation: is fighting it out more or less costly than co-operating?

“In humans, the flip to aggressive behaviour is calculated more consciously,” says Randolph Roth, a professor of history and sociology at Ohio State University. “We don’t need to sense that the queen is dead by realising that there aren’t any queen pheromones around, but we might realise that our family and property are not protected and our lives are at risk.”

Richard Nisbett, a professor of psychology at the University of Michigan, is investigating this issue — what causes people to respond aggressively in some social situations when in others they use persuasion, negotiation or charm to achieve the same goals. His work focuses on so-called honour cultures, societies whose members appear to resort to aggression far more readily than others.

In a recent set of experiments, Nisbett compared the behaviour of young, affluent, white college students from northern states of the US, where murder and violence rates are lowest, to that of students from southern states with the highest murder and violence rates in the country. The students, who believed that they were taking part in a standard psychological questionnaire, were escorted to an interview room. In half the trials, Nisbett arranged for a colleague to barge past rudely in the corridor, or to mutter an insult within earshot.

When students were walking down the corridor unimpeded, there was no difference between the behaviour of the northern and southern men. But in the “insult” scenario, southern men were more likely to report feeling insulted and fantasising about revenge. Nisbett also monitored the men’s hormone levels. He found that southern men experienced a significant increase in levels of testosterone and cortisone (a stress hormone), revealing that differences in their subjective perceptions were matched by a measurable biological response.

Nisbett ascribes the latent aggression he observed in southerners to an “honour culture” that he believes is born out of a tradition of cattle herding that has left a cultural imprint. When wealth is tied up in assets that are vulnerable to being stolen, he argues, it pays to be aggressive and to retaliate forcefully when threatened or insulted.

“Honour cultures tend to be those with herding economies, where someone can make off with your possessions and suddenly you are penniless,” Nisbett says. “One way you can protect against that is to make people realise they better not mess with you.”

The description has echoes of the philosophy of organised crime, in which vendettas tend to be settled swiftly, by private justice. Nisbett says: “Criminal trade such as drug dealing is like herding in that you can instantly lose an awful lot by people stealing your assets or your business.”

Nisbett’s work looks at conflict at the individual level, but war generally involves groups. Mark van Vugt, a professor of social psychology at the University of Amsterdam, has spent several years investigating what drives humans to band together in rival factions. He has uncovered an aspect of the male psyche, the “male warrior” effect, that he believes has driven men to stand side by side in battle since the earliest times.

Men have a phenomenal capacity for co-operation, Van Vugt says, but only when they are united against an enemy. In laboratory conditions, Van Vugt asked individual men if they wished to contribute some of their earnings, anonymously, to members of the same group. “They were strangers, in fact they did not have face-to-face contact, as they were put in different cubicles,” he says. “It would be rational for each member of the group to keep what they earn and hope that other people would contribute to the group so that they can get an extra share.”

Initially, the men did this. However, when they were told that their group was competing with a second group, they became significantly more likely to be altruistic to their own group.

Interestingly, women were initially more co-operative but their levels of altruism stayed the same in the face of an enemy threat. This offered an explanation for why war remains an almost entirely male pursuit, despite physical strength no longer being a limiting factor.

Van Vugt believes that he can explain the deep sense of camaraderie that attracts many men to military careers and the extraordinary sacrifices that men in particular can make for their country or cause. “The male warrior effect doesn’t explain the causes of a war, but it does explain why men join in,” he says.

He also believes that the male warrior effect has played a crucial role in enhancing cohesion; that warfare may have been the main driver for the formation of larger, more complex societies. “Arguably, inter-group conflict has caused groups to co-operate ever more closely,” Van Vugt says. “There are large costs involved in these ever larger social groups, but forming alliances could be the ticket to survival.”

An intriguing example of this effect comes from two economists — Russell Sobel, of the University of West Virginia, and Brian Osoba, of Central Connecticut State University — who specialise in the economics of street gangs. They argue that gangs emerge when the government fails to protect younger individuals from violence. On the basis of monthly gang membership and homicide in Los Angeles, their data suggests that an increase in homicide predicts gang membership, but that the opposite is not true. Violence results in gangs but gangs do not result in violence. In fact, Sobel and Osoba’s work suggests that gangs are effective in limiting violence. Being a member of a gang makes economic sense because the individual believes that it will increase his or her chances of survival and prosperity.

Sobel and Osoba say that law-enforcement strategies to break up gangs are ineffective in reducing street violence. Their work also suggests that even when apparently engaged in conflict, human society seeks to organise itself in a way that lowers violence.

By beginning to quantify the social trade-offs involved in the decision to fight, scientists have provided a new platform for speculation about whether conflict pays more or less today than it did in the past. Richard Nisbett argues that a move away from herding economies has raised the cost and lowered the potential benefit of raiding or violent retribution. In post-industrial societies, individual assets are harder to steal.

Historical evidence appears to support this view. The criminologist Manuel Eisner, of the University of Cambridge, has assembled hundreds of estimates of murder rates in Western Europe based on regional records kept between 1200 and the mid-1990s. In every country he has analysed, murder rates declined steeply — for example, there were 24 murders per 100,000 Englishmen in the 14th century, but by the early 1960s there were only 0.6.

“There has been a very long-term downward trend of interpersonal violence,” Eisner says. “From the 1830s, across Europe, there was a civilising process. You see changes in patterns of self-control. As states develop monopolies of power they increase the protection of individuals within it and there is a general pacification within the state.”

Of course, since the 1830s, warfare has taken place on a larger scale than ever before, and the sovereignty and success of nations depends on the ability to engage in international warfare. But though the American comedian George Carlin said that “fighting for peace is like screwing for virginity”, evidence suggests that war can pave the way to more peaceful societies.

Death rates in recent wars are far below those typical in tribal societies. While it is impossible to be sure of death rates in conflict among our hunter-gatherer ancestors, studies of contemporary non-state societies suggest that they were likely to have been high. Lawrence Keeley, an archaeologist at the University of Oxford, has gathered figures on the percentage of male deaths through warfare in hunter-gatherer societies in areas such as the New Guinea highlands and the Amazon rainforest.

Extensive genealogies over five generations of the Jivaro people in the Andes, for example, showed that more than 60 per cent of adult deaths were a result of intentional killing, ie, from external raiding and internal feuding. Across other tribal societies, levels of more than 30 per cent of adult deaths from intentional killing were common. If the wars of the 20th century had killed the proportion of the population that died in a typical tribal war, there would have been two billion deaths.

The technological sophistication of war can make it seem a recent invention. But evidence suggests that primordial harmony is a myth and that violence is in decline. Human society appears to be seeking a less violent state. Within nations, publicly appointed officers enforce peace. As the world becomes increasingly interconnected, we will have more to lose by attacking our enemies. World peace is still a distant prospect, but Einstein should take heart. We seem to be moving in a more peaceful direction.