Mark Twain couldn't have been further from the truth when he wrote in an essay, "Man is the only animal that deals in that atrocity of atrocities, War."
In the 1970's, chimpanzee expert Jane Goodall documented that humanity's relatives could commit acts of violence against each other.
"We used to think it was only humans who waged war, but we find that chimpanzees, like humans, have this rather unpleasant ability to create an in-group and an out-group."
And a new study published Wednesday in the journal Nature is renewing the debate on why chimpanzees injure, maim and even kill other chimps.
Is chimpanzee violence natural, or is it the result of human pressures put on them? Find out in this Newsy video.