This article examines changes and continuities in the epistemic and methodological presence of “race” in British imperial demography from 1920 to 1960. It does so in relation to population-level interventions aimed at improving reproduction in the New Hebrides. Through an examination of the sex ratio in relation to debates about demographic decline, the article describes aspects of how sexual selection was connected to race thinking. Taking a balanced sex ratio as a marker of well-adapted, healthy populations—biologically and culturally—the British authorities (...) in the New Hebrides attempted to regulate the bride price in an attempt to level the imbalanced sex ratio. They believed that this intervention would reduce the marriage age of men while also appeasing missionary agendas of changing marriage and kinship practices. I use the metaphor of a “watermark” to think through the conceptual and methodological absent/presence of race in colonial demography and colonial administrators’ attitudes toward and interventions in local reproductive practices. (shrink)