Homicide adaptations

a r t i c l e i n f o We propose Homicide Adaptation Theory as a new explanation for why people kill. Multiple homicide mechanisms have evolved as effective context-sensitive solutions to distinct adaptive problems. Killing historically conferred large fitness benefits: preventing premature death, removing cost-inflicting rivals, gaining resources, aborting rivals' prenatal offspring, eliminating stepchildren, and winnowing future competitors of one's children. Homicidal ideation is part of evolved psychological design for killing, functioning to mobilize attention, rehearse scenarios, calculate consequences, and motivate behavior. Because being killed inflicts temporally cascading costs on victims, selection has forged death-prevention strategies, producing co-evolutionary arms races between homicidal strategies and anti-homicide defenses. The murder of an individual or his close kin are among the greatest costs that can be inflicted on any individual. The dead cease to contribute to their own affairs and cannot actively influence the affairs of their families, friends, or enemies. Wherever written laws exist, killing is always singled out as a crime. No other infraction comes attached with greater punishment. Where written laws are absent, killing typically constitutes a major cause of death, sometimes accounting for the mortality of a third of all males (Keeley, 1996). Although cultures with written laws, hired police forces, and the prospect of imprisonment have substantially lower homicide rates than cultures lacking them the lifetime odds of dying by the hand of another in modern societies run as high as one in twenty-six for certain subgroups , such as inner-city males (Ghiglieri, 1999). In this paper, we review data on patterns of homicide in the United States and around the world. We introduce our evolutionary theory of homicide and discuss how adaptationist logic can both explain