Scientists have observed an extremely rare chimpanzee “civil war,” a conflict that has killed at least seven adults and 17 infants, and which sheds new light on the nature of warfare in humans, according to a study published on Thursday in Science. Male chimpanzees are often aggressive to outsiders, but it is unusual for chimps to kill former members of their own social groups. Though Jane Goodall and her colleagues observed one famous example—the Gombe Chimpanzee War of the 1970s, which resulte