Annexing territory, sending out scouting groups, beating enemies to death and eating babies. It may sound like a plot to a particularly violent video game, but it's really just chimpanzees, giving us some serious insight into human nature.
Chimpanzees have been known to kill, but a study performed over the course of 10 years on a group of males at Ngogo in Uganda's Kibale National Park has shown a much darker and much more human side to primate aggression.
Dr John Mitani and colleagues have observed a particularly large group of chimpanzees for a decade as they slowly expanded their territory, annexing land violently from rival tribes in the area. What's somewhat shocking is that instead of the wild, brutal violence we expect from the animal kingdom, the chimps' movements are organised and strategic.
Single-file scouting parties 20 strong will silently make their way into enemy territory. If they encounter large numbers of rival chimps, they hightail it back to their own lands.
Enemies with inferior numbers are not quite as lucky. The bands will gang up on their enemies, beating them to death with hands and feet. Females are generally spared useful as breeding stock. Babies are often eaten.
Why are the chimps taking over land?
Scientists believe the drive is survival. The primates, recognising that larger numbers means greater chance of survival, take over new land in order to have access to more fruit trees. With more fruit trees the females of the group have more to eat, and thus reproduce faster. It's safety in numbers, taken to the extreme.
Chimpanzees are close relatives of humans. Indeed, at one point in human history, hunting and gathering tribes behaved much like the primates observed by Mitani and associates. Should we conclude from this that war and aggression is in our blood, hardwired into our genetic makeup?
Not so, says Dr Mitani.
Mitani isn't oblivious to the lesson some people might draw from the study. "Invariably, some will take this as evidence that the roots of aggression run very deep," he says, and therefore conclude that war is our evolutionary destiny. "Even if that were true," says Mitani, "we operate by a moral code that chimps don't have."
Instead of highlighting the similarities between chimpanzees and humans, Mitani would rather us use this as a means to highlight the major differences between the two groups - morality.
Does Chimp Warfare Explain Our Sense of Good and Evil? [The Atlantic]