The peacemakers

摘要

Is aggressive behaviour innate or learned? In baboons, it seems, it is learned. A surprising natural experiment, reported in Public Library of Science Biology, an online journal, suggests that the level of violence in baboon society is culturally determined. The story begins in 1983, in the Masai Mara Reserve in Kenya. Robert Sapolsky, a primatologist at Stanford University, was five years into a study of the reserve's olive baboon population when one of the troops he had been observing suffered an outbreak of tuberculosis which killed half of its males. Since the source of the infection was a garbage dump being used as a food supply, and control of this dump was contested with another troop, the males who became infected and died were the more aggressive individuals in the troop-ie, those best fitted to the task of fighting for food. The result was that the level of aggressive behaviour within the troop dropped off markedly.