Chimpanzees
Authors of a new study on chimpanzees say their findings should put to rest some long-held questions about human intervention with the primates. Reuters

Murder is an act of aggression that "comes naturally" to chimpanzees, according to a new study published in the scientific journal Nature. Researchers found that killing has become an evolved tactic for the species, and is usually done by groups of male chimps, in an effort to have better access to land, mates and other resources. The study was co-written by over 30 scientists worldwide who looked at death among 18 chimpanzee communities in Africa for over five decades.

Primatologists have long debated whether human interference, including destroying habitats and providing food, increased aggression in chimpanzees. But results from the study "should finally put an end to the idea" that violence in wild chimpanzees is a product of human interference, Joan Silk, an Arizona State University professor, said in an accompanying commentary for the journal.

"It's a natural behavior -- it's not something that we've induced by disturbance or intervention," said Susanne Shultz, an evolutionary biologist at the University of Manchester.

Because of similarities between chimps and humans, anthropologists said they also now have a better understanding of human violence. “Observations that chimpanzees kill members of their own species have influenced efforts to understand the evolution of human violence,” said University of Michigan anthropologist John Mitani.

But there are important differences between humans killing each other and chimpanzee deaths, Mitani said. "There is considerable variation in rates of killing by chimpanzees living in different populations, so even in chimpanzees, killing is not inevitable," he said. "And, of course, we are humans and not chimpanzees. We have the ability to shape and alter our behavior in ways that they can't. We can alleviate considerable human suffering by harnessing that ability."