ABSTRACT
Kaplan argues that, in modern societies, fertility and, by extension, mate selection decisions are governed by physiological mechanisms, by fitness maximizing motives, and by individuals' assessments of optimal levels of parental investment. The model of fertility presented by Kaplan and colleagues leaves unexplained the possible interpersonal subjective and bases of men's fertility decisions. When women's education is entered into the model, the effect of men's education disappears. Characteristics of men's heterosexual relationships, such as number of prior relationships or length of relationship, or of the relationship context in which children were born, are significant predictors of their parental investments and of their children's outcomes. Men's contributions to families can best be understood in the context of the contributions of other family members. Mate selection and fertility decisions, in particular, require theories and data that speak to the interpersonal, or how one partner affects the decision making of the other partner.
