This paper presents an historical perspective on the interaction between conservation science and policy. Drawing on a synthesis of studies of the history of conservation, and combining this with work in science policy and related fields, it considers the implications of a shift, beginning in the 1960s, in the politics of expertise. Before that time, scientific evidence and interpretations were usually discussed within restricted arenas of experts and policymakers. After the 1960s, they instead increasingly became matters of public debate. This shift had several consequences for conservation. It encouraged scientists and other advocates to present conservation as a strictly scientific matter, that was based on authoritative, quantitative and transparent – and therefore publically defensible – processes. Conservation science itself evolved to emphasize spatial concepts and practices that could provide the basis for rule-based, replicable procedures for determining conservation priorities. This account therefore illustrates the insights to be gained from reconsidering the history of conservation in terms of our understanding of the evolving status and social roles of expertise.