A skull from Nataruk, northern Kenya, showing the traumatic lesions that caused this mans death. Violence and warfare have shaped human societies for many thousands of years, but the origins of inter-group conflict in the archaeological record are controversial, dependent on how such conflicts are defined and recognized, as well as on the lottery of preservation. Marta Mirazón Lahr et al. report fossil finds that point to a case of inter-group violence among hunter-gatherers in the early Holocene. Ten out of twelve skeletons, discovered near what was once a small lagoon, show evidence of having undergone violent deaths. There were no signs of deliberate burial, and several individuals have multiple major traumatic lesions including an obsidian bladelet embedded in one of the skulls. The authors interpret this assemblage as the aftermath of a violent inter-group encounter that took place some 10,000 years ago on the fertile shores of Lake Turkana. Cover: Marta Mirazón Lahr & Fabio Lahr.