Researchers have documented a permanent split in the largest-known group of wild chimpanzees in Kibale National Park, Uganda, which led to a lethal civil war. The study, published in the Science journal, traced 30 years of chimpanzee behavior and found a transition from cohesion to polarization among the Ngogo population starting in 2015. The two clusters stopped reproducing with each other and Western males began patrolling Central territory to expand their domain. By 2017, Western chimps began attacking Central chimps, killing at least seven adult males and 17 infants in the Central group. The researchers suggest this could help scientists better understand the roots of human conflict.