Behavioral Sciences and the Law Behav. Sci. Law 18: 309–329 (2000) Copyright Þ 2000 John Wiley & Sons, Ltd. A Brunswikian Evolutionary– Developmental Theory of Adolescent Sex Offending Aurelio Jose ´ Figueredo, Ph.D., 1 Bruce D. Sales, Ph.D., J.D., 1 Kevin P. Russell, M.A., 1 Judith V. Becker, Ph.D. 1 and Meg Kaplan, Ph.D. 2 A Brunswikian Evolutionary-Developmental model was developed to relate the sex offending behavior of ado- lescents to other forms of social deviance, tracing a his- tory of repeated frustration and failure in various competitive sexual strategies and escalation to more extreme means of obtaining sexual gratification. Four hypothetical constructs were proposed as stages in the development of sexual criminality: (1) Psycho-Social Deficiency (PSD); (2) Non-Criminal Sexuality (NCS); (3) Non-Sexual Criminality (NSC); and (4) Sexual Criminality (SC). Significant direct and indirect path- ways led from PSD to SC through both NCS and NSC, each time facilitated by an interaction with PSD. Although the causal orders between stages remain equivocal, the current results are consistent with our theory and establish the heuristic value of our theoretical approach, providing empirical support for otherwise counterintuitive predictions. This interpretation also offers hope for focusing preventative intervention at one major root cause of this unfortunate cascade of conse- quences, Psycho-Social Deficiency. Copyright 2000 John Wiley & Sons, Ltd. Evolutionary theory provides us with two principal alternative hypotheses regard- ing the proximate causation of human sexual coercion. The first is that there exists a specific behavioral adaptation for sexual coercion. Thornhill and Thornhill (1992) have hypothesized that the use of rape and other coercive sexual behaviors have an evolutionary history of promoting the reproductive success of the per- Correspondence to Aurelio Jose ´ Figueredo, Ph.D., Department of Psychology, 1503 E. University, P.O. Box 210068, University of Arizona, Tucson, AZ 85712, U.S.A. e-mail: ajf@u.arizona.edu 1 Department of Psychology, University of Arizona, U.S.A. 2 Columbia University College of Physicians and Surgeons and Sexual Behavior Clinic, New York State Psychiatric Institute, U.S.A.