Legal and Criminological Psychology (2002), 7, 1–13 © 2002 The British Psychological Society www.bps.org.uk Evolutionary theory and criminal behaviour Vernon L. Quinsey * Queen’s University at Kingston, Ontario, Canada Purpose. To provide an introduction to evolutionary psychology by describing some of its applications in the literature on the psychology of criminal and antisocial behaviour. Argument. Selectionist thinking is applied to ve areas: the relationship of age and sex to crime, the inverse correlation between degree of kinship and homicide, paedophilia, persistent antisociality, and sexual coercion. In each of these areas, ultimate causes of behaviour are distinguished from proximal causes. Ultimate causes are produced by selective forces in ancestral environments and are respon- sible for species typical characteristics. Proximal causes, in contrast, are contempor- aneous developmental, genetic, and environmental determinants of behaviour. Conclusions. The interplay between ultimate and proximal causation provides new ways of understanding old problems and is a fruitful source of research hypotheses. Evolutionary psychology can provide a powerful integrative perspective on criminal and antisocial behaviour. Evolutionary theories seek explanations of criminal behaviour involving ultimate causes of species typical characteristics. Ultimate causes are the features of ancestral environments that selected particular characteristics observable in present populations through their historical relationship with differential reproductive success and are distinguished from proximal causes, the mechanisms that produce the characteristic in the present environment. Ultimate causes address ‘why’ questions, whereas proximal causes address ‘how’ questions. Evolutionary theories are environmental and selectionist in orientation because past environments are posited to have selected characteristics of organisms by acting at the level of individual genes—specifically, causing genes associated with reproductive success to increase in frequency over generations (Crawford & Anderson, 1989). Notwithstanding the fact that the effects of ultimate causes are mediated genetically, evolutionary theories are also environmental in a more proximal sense because genes frequently cause organisms to act differently in different environmental contexts. Behaviours that are determined by the proximal environment are termed facultative, as opposed to obligate behaviours that develop to a large degree independently of variations in environmental context. Characteristics of organisms that are produced by natural selection are adaptations. Adaptations, following Williams (1992), are identified by their functional design, their Invited paper. *Requests for reprints should be addressed to V. L. Quinsey, Psychology Department, Queen’s University, Kingston, ON, Canada K7L 3N6 (e-mail: quinsey@psyc.queensu.ca). 1