Men universally express a preference for youth in a long-term mate, presumably an evolved desire originating from the close and recurrent statistical association between a woman's age and her residual reproductive value (future reproductive potential). As a consequence, we hypothesized a positive correlation for men (but not women) between the number of children desired and preferred spousal age difference — a context-specific shift in mate preference depending on whether the man is pursuing a “quality” or “quantity” reproductive strategy. We tested this hypothesis with data provided by 9809 participants from 37 cultures located in six continents and five islands. Between-culture analyses confirmed the hypothesis, even after statistically controlling for preferred age at first marriage, current age of participant, and current marital status. Discussion notes limitations and focuses on other possible context-sensitive shifts in mate preferences.