Chimps Evolved to Become Natural Born Killers

Chimpanzees and humans have a lot in common, including engaging in coordinated attacks against perceived rivals, according to a new study. While many have argued in the past that human influence is to blame for this violent behavior, the recent findings indicate that chimps actually evolved to become natural born killers.

The new research, published in the journal Nature, sheds light on the subject, suggesting that human impact - such as habitat destruction or food provisioning - does not influence this chimp-on-chimp aggression.

"Violence is a natural part of life for chimpanzees," Michael Wilson, the study's lead author and an associate professor of anthropology at the University of Minnesota, told Live Science. "They don't need to be fed bananas to kill each other."

Over the course of five decades, scientists collected data on 18 chimpanzee groups living in Africa. The chimps exhibited 152 killings, including 58 that the scientists observed, 41 that were inferred and 53 suspected killings in 15 communities, the researchers said.

Surprisingly, these acts of violence did not depend on human impact, according to Wilson. Instead, attacks were more common at sites with many males and high population densities.

"Most killings involve gang attacks," Wilson told Discovery News. "When attacking adults, many attackers pile onto the victim. They pin the victim to the ground and hit, kick and bite the victim."

These attacks are so violent, he added, that the chimps can even damage internal organs, break bones, and cause major puncture wounds with their strong and sharp teeth.

While this level of violence may seem extreme, researchers believe there is a use for it. Joan Silk, a professor in the school of Human Evolution and Social Change at Arizona State University, who was not involved in the study, speculates that chimps evolved this way because circumstances during their daily lives call for it. For example, such aggression is useful when encountering members of neighboring groups when they are on their own, Silk pointed out to Live Science.

But that doesn't mean chimps are always out for blood.

"Overall, aggression makes [up] a small percentage of their daily lives," Wilson said, adding that, "our behavior affects them, but it's not affecting them as people have suggested in the past, resulting in aggression."