20:03 18 July 2013 by Bob Holmes
Is war in our blood? Perhaps not, if you believe a controversial new study that suggests violence in primitive cultures is overwhelmingly the result of personal squabbles, rather than organised violence between two different groups. The finding contradicts the popular view that humans have evolved to be innately warlike.
In recent years, many anthropologists and evolutionary biologists have come to believe that warfare arose deep in humans’ evolutionary past. In part that is because even chimpanzees exhibit this kind of intergroup violence, which suggests the trait shares a common origin. Proponents of this view also point to the occurrence of war in traditional hunter-gatherer societies today, such as some notoriously quarrelsome groups in the Amazon, and hence to its likely prevalence in early human societies.
Yet the archaeological record of warfare in early humans is sketchy, and not all contemporary hunter-gatherers make war.
In a bid to resolve the issue, Douglas Fry and Patrik Soderberg of Åbo Akademi University in Vasa, Finland, turned to the Ethnographic Atlas, a widely used database that was created in the 1960s to provide an unbiased cross-cultural sample of primitive societies.
From this, Fry and Soderberg selected the 21 societies that were exclusively nomadic hunter-gatherers – groups that upped sticks to wherever conditions were best – without livestock or social class divisions. They reasoned that these groups would most closely resemble early human societies.
The researchers then sifted through the early ethnographic accounts of each of these societies – the earliest of which was from the 17th century, while most were from the 19th and 20th centuries – and noted every reference to violent deaths, classifying them by how many people were involved and who they were. The records include accounts of events such as a man killing a rival for a woman, revenge killings for earlier deaths, and killing of outsiders such as shipwrecked sailors.
The pair found that in almost every society, deaths due to violence were rare – and the vast majority of those were one-on-one killings better classified as homicides than as warfare. Indeed, for 20 of the 21 societies, only 15 per cent of killings happened between two different groups. The exception was the Tiwi people of northern Australia, where intergroup feuds and retaliatory killings were common.
Fry and Soderberg say this suggests that warfare is rare in such primitive societies and may instead have become common only after the rise of more complex societies just a few thousand years ago. If so, then warfare would have likely played only a minor role in human evolution.
Not everyone agrees. For one thing, the data set Fry and Soderberg used is essentially a collection of anecdotes rather than a systematic survey of causes of death, says Kim Hill, an anthropologist at Arizona State University in Tempe. They are relying on the people who originally noted down these events to have included all the important details.
Moreover, they focus only on nomadic foragers and exclude any sedentary foraging societies – groups that would have foraged from a permanent base. Yet these sedentary foragers would probably have occupied the richest habitats and so would have been most likely to be involved in wars over territory, says Richard Wrangham, an anthropologist at Harvard University.
Fry and Soderberg are probably correct that most violent deaths are the result of homicide, not warfare – that was even true for the US during the Vietnam War, says Sam Bowles at the Santa Fe Institute in New Mexico. He has put forward the idea that altruism evolved out of the need for our ancestors to cooperate during times of war. But even if warfare is relatively uncommon, it can still exert an important evolutionary force, he says.
Journal reference: Science, DOI:10.1126/science.1235675