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Life history theory postulates tradeoffs of current versus future reproduction; in both developed and developing nations today, women face evolutionarily novel versions of these tradeoffs. Here we use a nonlinear dynamic model to explore: [1] the general issues of tradeoffs of education, work, and current fertility; [2] some specific examples (e.g., what increase in fertility will compensate for particular delays of age at first birth under given conditions). Finally, we model a largely unrecognized issue. Demographic transitions of the past have been characterized by decreases in fertility accompanied by (sometimes quite large) increases in per capita investment in offspring. The Rio Conference and its followup highlighted the conflicts between low-fertility, high-consumption, versus highfertility, lower consumption strategies — yet we have few ways to make testable predictions about future conflicts. We explore outcomes when impending resource constraints differentially affect short-generation-time-strategists, versus delayed-reproduction-resource-acquirers. The conditions favoring delayed fertility with resource accumulation are highly constrained; under almost all conditions reproduction in the early 20s leads to the greatest lineage success for women in the models.

This paper draws on evolutionary life history theory to examine nonmarital births in the context of women’s ability to secure male parental investment for their offspring. While nonmarital births are usually defined with respect to marital status the day of parturition, we adopt a more nuanced approach that corresponds to men’s willingness to commit to family obligations. Our approach distinguishes between marriages preceding pregnancy, marriages occurring between pregnancy and birth, marriages immediately following birth, and births that are not followed by marriage to the child’s father. Using retrospective marital and reproductive histories from the Panel Study of Income Dynamics (PSID), we observe a range in women’s life history outcomes (fertility and marital measure) corresponding to this range in male commitment around the time of first birth. Self-selection biases are not examined in this analysis, although their implications are discussed.