Evolutionary psychology holds that the basic perceptions of self-interest shared by all normal members of a given species are products of a long history of natural and sexual selection and thus may be expected to exhibit design for promoting "fitness" (genetic posterity) in ancestral environments. The authors intend that "perceptions of self-interest" should encompass appetites and aversions both for relatively specific pleasures and pains and for such intangibles as social status and self-esteem, and even that it should encompass processes that are not psychological in any ordinary sense of this word. Human immune systems and cell membranes, for example, operate outside awareness, but they participate in perceiving and defending interests nonetheless. The authors maintain that well-known patterns of homicide are in many way predictable, reflecting as they do the biological and anthropological mandates that influence much of homo sapiens' behavior. Aggressive male responses to perceived competition for resources and victimization patterns that predominate among family homicide (e.g., the high risk to stepchildren) are but a few of the topics they find wholly explainable from a socioevolutionary perspective. The chapter emphasizes, however, that the argument presented should not be interpreted as excluding the other main theories that help explain homicidal behavior. 71 references