Chimpanzees are mostly peaceable creatures, spending much of their time foraging for food and grooming each other. But occasionally they kill their own kind. Why they engage in these lethal bouts of aggression has been uncertain. One theory holds that killing is an evolved strategy for reducing competition for resources; another posits that human disturbance—including hunting and deforestation—has triggered the behavior. Now a large study of killings in chimp communities across Africa has cast new light on the dark side of our closest living relatives.

Michael Wilson of the University of Minnesota and his colleagues amassed data on chimps in 17 communities at 10 sites in west, central and east Africa whose members had long been observed by researchers. For each community the team obtained data on demography, population size, ranging behavior of the group, and so forth. The team also compiled data on bonobos from four communities, to determine whether bonobos really are less aggressive than chimps, as is commonly asserted. Wilson presented the study results on April 12 at the annual meeting of the American Association of Physical Anthropologists in Portland, OR.

Read more at Scientific American