The evolutionary perspective, particularly as it pertains to behavioral sex differences, has been underappreciated in adolescent psychology. This perspective, embodied by ethology and evolutionary psychology, provides several advantages to scholars of adolescence. It fosters integration of adolescent psychology into the biological sciences, including genetics, neuroscience, endocrinology, and medicine. It offers a species-wide perspective, focusing attention on timeless, universal behaviors in lieu of a parochial emphasis on one's own society. It emphasizes functional analysis of normal behaviors, providing a vantage point for understanding individual variants such as male risk taking, cultural variants such as polygyny, and pathological variants such as obesity. It furnishes a theoretical framework for understanding how the normal adolescent achieves independence from parents, secures a mate, and prepares for parenthood. This perspective is now being applied to the study of genetically programmed alternative developmental pathways to meet various environmental conditions, under the rubric of life history theory.