A new study suggests that, just in terms of sheer numbers of acts of aggression, bonobo males are more violent than male chimpanzees. However, because bonobos live in matriarchal societies, the males weren’t observed to engage in organized mass violence like male chimpanzees do, so they weren’t observed to kill each other. Bonobos are more difficult to study than chimpanzees because they live deep in the remote jungle of just one country.