Of all the world's animals, chimps and humans are some of the only to coordinate attacks on members of the same species. A new study concludes that, for chimpanzees, this kind of lethal aggression is "normal" and common. And by normal, the researchers mean the behavior stems from evolved tendencies, and not a response to human pressures, such as habitat loss.

Image: Sergey Timofeev/Shutterstock.

Share This Story