What characteristics do people prefer in potential mates? Previous studies have explored this question, discovering that preferred characteristics vary by people's sex and sexual strategy, but have implied that these preferences remain constant across the lifespan. We suggest, however, that systematic variation exists in individuals' mate preferences across the lifespan, as they shift their investments from mating toward parenting. We suggest that the characteristics of a potential mate can be viewed as affordances that assist or hinder an individual in achieving certain fundamental goals. Incorporating the framework of Life History Theory with this affordance-management approach to social behavior, we propose that an individual's life stage, sex, and life history strategy together serve as the basis for these goals and thereby shape the characteristics people seek in potential mates. Using data collected from participants aged 18-45 recruited on Amazon's Mechanical Turk, we tested a range of hypotheses derived from our approach. In general, results provide mixed support for a role of life stage in shaping mate preferences. For example, nurturance and social competence were viewed as more necessary characteristics in a mate by participants invested in parenting. Moreover, as their investment in mating increased, females expressed a greater preference for ambition in their potential mates, but males did not. Other predictions were not borne out, however, suggesting that there is still much to be learned from investigating the relationship between life stage and mate preferences.