A violent encounter between the two factions of Ngogo chimpanzees Aaron Sandel A once harmonious group of wild chimpanzees has split into two, leading to intractable conflict and escalating violence. Researchers say the rift suggests that human wars are a deeply rooted part of our nature, rather than something that emerged recently as our culture became more complex. Aaron Sandel at the University of Texas at Austin and his colleagues analysed 24 years of social networks, 10 years of GPS-based ranging and 30 years of demographic data on the chimpanzees ( Pan troglodytes ) in Kibale National Park, Uganda. “We want to be especially cautious with the words we use,” says Sandel. “These are chimps. War and civil war are terms that have a special significance for humans. What we saw isn’t civil war. But it does have important parallels.…