![Fighting Bonobos ( Pan paniscus) on a tree branch](https://cdn.mos.cms.futurecdn.net/vjfBfmFmpcsBxkrx7NHWLX-320-80.jpg)
'Hostilities began in an extremely violent way': How chimp wars taught us murder and cruelty aren't just human traits
Can chimpanzees wage war? In this excerpt from "The Beast Within: Human as Animals," scientific researcher Jessica Serra looks at the dark side of our cousins' behavior.