The human race spends a disproportionate amount of attention, money, and expertise in solving, trying, and reporting homicides, as compared to other social problems. The public avidly consumes accounts of real-life homicide cases, and murder fiction is more popular still. Nevertheless, we have only the most rudimentary scientific understanding of who is likely to kill whom and why. Martin Daly and Margo Wilson apply contemporary evolutionary theory to analysis of human motives and perceptions of self-interest, considering where and why individual interests conflict, using well-documented murder cases. This book attempts to understand normal social motives in murder as products of the process of evolution by natural selection. They note that the implications for psychology are many and profound, touching on such matters as parental affection and rejection, sibling rivalry, sex differences in interests and inclinations, social comparison and achievement motives, our sense of justice, lifespan developmental changes in attitudes, and the phenomenology of the self. This is the first volume of its kind to analyze homicides in the light of a theory of interpersonal conflict. Before this study, no one had compared an observed distribution of victim-killer relationships to ‘expected’ distribution, nor asked about the patterns of killer-victim age disparities in familial killings. This evolutionary psychological approach affords a deeper view and understanding of homicidal violence.