Life history theorists have proposed that humans have evolved to be sensitive to specific features of early childhood environments and that exposure to different environments biases children toward development of different reproductive strategies, including differential pubertal timing. The current research provides a longitudinal test of this theory. Assessments of family environments, based on interviews with mothers and fathers, were conducted in preschool, and children were then followed prospectively through middle childhood. Adrenal hormones were assayed in a selected subsample of 120 children (73 girls) at age 7, and parent and child reports of secondary sexual characteristics were collected in the full female sample of 180 girls at age 11. Higher quality parental investment (from both mothers and fathers) and less father-reported Marital Conflict/Depression forecast later adrenarche. Older age at menarche in mothers, higher socioeconomic status, greater mother-based Parental Supportiveness, and lower third-grade body mass index each uniquely and significantly predicted later sexual development in daughters. Consistent with a life history perspective, quality of parental investment emerged as a central feature of the proximal family environment in relation to pubertal timing.