Chimps Naturally Violent Without Influence of Humans, 54-Year Study Says

Chimps are naturally violent and not because of their interactions with humans, suggests a new, 54-year study that provides a long-term look at the apes' warlike behavior.

Researchers have long debated the origins of chimps' sometime lethal aggression, especially towards each other. Some claim the violence is innate, while other insist it's somehow linked to human interference.

Now, with the help of University of Minnesota anthropology professor and study leader Michael Wilson, the answer is clear.

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"Violence is a natural part of life for chimpanzees," Wilson told LiveScience.com. "They don't need to be fed bananas to kill each other. Studies of chimpanzee violence have been especially influential in how people think about the origins of human warfare. Some people have argued that human warfare is a recent cultural invention, the result of some other recent development such as the origin of agriculture."

The study, which was published Wednesday in the science journal Nature, compared chimps with bonobos, two species thought to share a common ancestry with humans. Researchers then compared their aggressiveness over numerous sites for extended periods of time.

"This is a very important study, because it compiles evidence from many sites over many years, and shows that the occurrence of lethal aggression in chimpanzees is not related to the level of human disturbance," Joan Silk, a professor at Arizona State University who was not involved in the study, told LiveScience.com in an email.

Researchers who have held on to the theory that human interaction is involved in chimpanzees' behavior have dismissed the study, according to The New York Times.

"The statistics don't tell me anything," Robert Sussman, an anthropologist at Washington University, told the newspaper, adding that he supports the theory that humans put pressure on chimpanzee societies that results in killings. "They haven't established lack of human interference."

Another anthropologist, Brian Ferguson at Rutgers University, questioned the study's measures of human impact, according to The Times. Ferguson argued that human impact "can't be assessed by simple factors."

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