WHAT DOES science teach us about war? An insight comes from Jane Goodall’s seminal study of the battles of the Kasakela chimpanzees of the Gombe Stream National Park in Tanzania. During her study the Kasakela chimpanzees, growing too large in number, split in two — a smaller Kasakela group and a new Kahama group emerged. To start with, the groups shared the rain forest peaceably, and when their members met they were pleasant. They were old friends.

But after about a year, once the new collective loyalties had firmed up, the two groups grew mutually hostile, and they fell into war. Bands of males from one would descend on bands of the other, killing the males and abducting the females (perhaps chimps, too, dream of 72 virgins). Eventually, after appalling scenes of multiple mutilation and murder, the Kasakelas drove the Kahamas to extinction.

The suspicion we primates have of other groups is so strong that academics can experiment with it. In one study on human beings, the psychologist Muzafer Sherif, of the University of Oklahoma, collected 22 local boys aged 11. The boys didn’t know each other, but they were of similar backgrounds.

Sherif divided the boys arbitrarily into two groups of 11, which he separated on different camp sites in the Robbers Cave State Park. What would the two groups do over the next few weeks? Would they intermingle? Or would they separate even farther apart in the near-endless spaces of the park? Or would they name themselves the Rattlers and the Eagles, declare war, and meet for the sole purpose of beating the hell out of each other? Yup, you guessed it.

The conclusion from these and related studies is that, when different group identities exist, war is the default position. Nature is unkind, so we primates have evolved to be highly suspicious of anything different, and our suspicions will spill over into the instinctive killing of strangers. War is endemic amongst tribal peoples, and Charles Darwin reported that “the tribes inhabiting adjacent districts are almost always at war with each other”.

In Science magazine last week Andreas Olsson and his colleagues, from the psychology departments of New York and Harvard Universities, reported on their latest study of human group paranoia. They presented subjects with pictures of four faces, two black and two white, accompanying each presentation with an unpleasant electric shock. Not surprisingly, the subjects — as judged by their sweating responses — learnt to dislike all four faces and to fear their repeated presentation. Yet, on being shown the faces again, without shocks, the black subjects soon lost their fear of the black faces, and the white subjects soon lost their fear of the white faces, but neither race easily lost their fear of the faces of the different race.

Racism is not instinctive — the different human races evolved too recently for that instinct to have developed — but group loyalties are deeply felt, and this experiment shows that both black and white Americans have learnt to treat the other race as a different group, and that while we humans easily forgive members of our own group their transgressions, we treat the transgressions of members of other groups as casi belli.

The psychologist Judith Rich, in her book The Nurture Assumption, explained how separate group identities are maintained when different cultures share the same urban space. It is a matter of critical mass. When a single Muslim family, say, inhabits a northern town, it acclimatises to northern culture, chip butties and all. But once a school contains sufficient numbers of Muslim children, they forge their own separate, potentially paranoid, identity.

The lesson of science is that a heterogeneous society aspiring to internal peace must follow the melting pot and induct all children into a common culture. That may involve flag worship and other embarrassing ceremonies, but the celebration of diversity may be, biologically, a mistake.

Miscegenation helps, too. In his study, Olsson found that subjects who had dated members of the other race were swifter to lose their racial fear than those who had not. It probably shows that the more intimately we know members of different groups, the more likely we are to accept them as “us”. Biology confirms that the breaking down of cultural barriers promotes peace.

The author is Vice-Chancellor of Buckingham University

Times Recommends

• In the real world, the public sector must pay
• Playing politics in a land of double Dutch
• Be like the plinth people: not set in stone