Sex Biases in Patterns of Parental Investment

Most research on human parental investment has focused on overall parental effort or resource allocation, overlooking the fact that human investment spans a broad suite of material, instructional, and social forms of investment. This array of investment enables examination of how evolutionary processes have elaborated parental care into distinct domains. Where daughters and sons historically faced different recurrent adaptive problems, selection should have favoured biases in parental investment that cultivate in each offspring the competencies relevant to its sex-specific challenges (e.g., navigating greater reproductive costs for daughters; navigating contest competition for sons). Likewise, mothers and fathers should differ in parental investment domains where their own evolutionary and life histories afforded greater sex-specific expertise. To test these hypotheses, we used linear mixed-effect models to analyse 105 adults' (49.5% female) ratings of parental investment received across 73 behaviours organised into 13 domains. Results were largely consistent with predictions. Daughters received more parental investment in mating and relationship guidance, protection, and material support. Sons received greater parental investment in athletic training, permissiveness regarding sexual behaviour, and competitive encouragement. Mothers invested more than fathers in direct care, bonding, social and moral guidance, and discipline. Fathers invested more in athletics, and mechanical and practical skills. Domains linked to adaptive challenges common to both sexes (e.g., direct care) showed no offspring-sex differences in parental investment. The patterns accord with the evolutionary hypothesis that parental investment maps onto sex-differentiated adaptive problems. Discussion explores hypotheses about the interactions between socialisation practices of parents and sex-linked predispositions in offspring.