Published in Evolution and Human Behavior
April 2011, online July 2011
We use data from the National Incident-Based Reporting System to examine the effects of offender and victim age on whether male offenders commit sexual assault while robbing women. Restricting analyses to robberies reveals the offenders' age preferences since it allows one to control for the effects of opportunity. We find that robbers of all ages are most likely to sexually assault women at ages 15–29 years, ages when their reproductive potential is highest. However, in contrast to the idea that rape is a direct adaptation, victims are no more likely to be raped than sexually assaulted at these ages. The age of the offender is also a strong predictor of sexual assault. The likelihood that a robber commits a sexual assault increases from age 12 years until he reaches his early thirties when it begins to decline. This age pattern corresponds, to some extent, to age differences in the male sex drive.