The scientists looked for evidence of this ghastly activity among four million recorded deaths in more than a thousand different mammals, from shrews to primates. On top of that, they compiled a history of human slayings. One pattern stood out pretty clearly: Lethal violence increased over the course of mammal evolution. While only about 0.3 percent of all mammals die in conflict with members of their own species, that rate is sixfold higher, or about 2 percent, for primates. Early humans likewise should have about a 2 percent rate—and that lines up with evidence of violence in Paleolithic human remains. The medieval period was a particular killer, with human-on-human violence … Continue reading Erika Engelhaupt