From infancy until early adulthood, men have higher mortality rates due to external causes than do women. Human evolutionary behavioral scientists have framed this sex difference in pre-adulthood mortality risk as an outcome of sex-specific intrasexual competition, resulting in a higher propensity for physical risk taking in males. The current research builds upon this work, by retrospectively exploring patterns of injury occurring in childhood and adolescence. We predicted sex-specific effects with respect to the ways individuals adjust to their environments behaviorally, including: life history strategy, childhood and adolescent injury, and age at sexual debut. Seven hundred eighty five (173 men, 612 women) U.S. university students completed an anonymous questionnaire including metrics considering sociodemographics, significant childhood and adolescent injuries (including injury severity and quantity of stitches received), perceived neighborhood safety, age of incidence for first sexual intercourse, number of sexual partners, and life history strategy. Individuals with faster life history strategies were more likely to have sustained serious injuries in their youth (requiring stitches, surgery, or medication). Also, those with a Fast LHS are more likely to be male, define their neighborhoods as dangerous, and have their first sexual encounter at an earlier age. Adaptive behavioral responses triggered by latent factors in local ecology may promote riskier behaviors in modern environments, helping to explain the etiology of risk-taking behaviors and injury among youth today. We discuss results in terms of predictive human evolutionary theory.