Drawing on Belsky, Steinberg, and Draper's evolutionary theory of the development of reproductive strategies, we tested a model of individual differences in girls' pubertal timing. This model posits that a history of psychopathology in mothers results in earlier pubertal maturation in daughters, and that this effect is mediated by discordant family relationships and father absence/ stepfather presence. The model was supported in a short-term longitudinal study of 87 adolescent girls. In the primary test of the model, it was found that a history of mood disorders in mothers predicted earlier pubertal timing in daughters, and this relation was fully mediated by dyadic stress and biological father absence. In families in which the mother's romantic partner was not the biological father, dyadic stress accounted for almost half of the variation in daughters' pubertal timing. Stepfather presence, rather than biological father absence, best accounted for earlier pubertal maturation in girls living apart from their biological fathers. We propose that stepfather presence and stressful family relationships constitute separate paths to early pubertal maturation in girls.