Matthew Zefferman: Arizona State University

Combat veterans in western industrialized societies can develop a collection of symptoms classified as post-traumatic stress disorder (PTSD). The origins of PTSD are a mystery. Some posit that it has deep evolutionary roots as a mechanism for avoiding and responding to harm. Others posit that it is socially constructed and perhaps unique to industrialized societies. I propose, with a gene-culture co-evolutionary theory of combat stress, that both perspectives are partially right and incomplete. This theory explains additional puzzling aspects of combat stress, such as the origins of “moral injury.” I support this new theory with evidence from ethnographic research and interviews with Turkana warriors from northern Kenya.