This proposal represents an approach to prevention in which evolutionary theory provides a unifying theoretical framework, which implies that diverse problems are due to social environments that are unfavorable for the expression of prosocial behaviors, instead eliciting a variety of self-oriented or exploitative behaviors. Systematic efforts to reduce multiple problems among youth (e.g., substance use, risky sex, depression, academic failure, etc.) need to look beyond the immediate issues to the social conditions that make the entire range of problems more likely. Programs should focus on modifying key social environments to nurture prosocial behavior and minimize the toxic or stressful conditions that give rise to behavioral problems in youth.