IS WAR in our blood? Perhaps not: it seems violence in primitive cultures is the result of personal squabbles, rather than organised group violence. Many anthropologists believe that warfare arose deep in humans’ evolutionary past. This is in part because chimpanzees exhibit the same kind of intergroup violence, suggesting a common origin for the trait. Yet the archaeological record of human warfare is sketchy. To find out more, Douglas Fry and Patrik Soderberg of Åbo Akademi University in Vasa, Finland, examined ethnographic accounts of 21 traditional societies of nomadic hunter-gatherers, reasoning that these groups would most closely resemble early human societies. Accounts dating from the 17th century showed that violent deaths were rare; the vast majority were one-on-one killings not warfare (Science, doi.org/m88). Fry and Soderberg conclude that warfare may have become common only after the rise of complex societies. If so, it would have had only a minor role in our evolution. Not everyone agrees. Sedentary foragers were excluded from the study, but they would have occupied the richest habitats, so were most likely to have wars over territory, says Richard Wrangham at Harvard University. Even if warfare is uncommon, it can still exert an important evolutionary force, adds Sam Bowles at the Santa Fe Institute in New Mexico. This article appeared in print under the headline “Vendettas not war?