During the mid-nineteenth century, the eminent British zoologist Alfred Newton recognized that some of the ideas embedded in Origin of Species provided new scientific rationales for the preservation of endangered species. He then embarked on a twenty-five-year-long campaign for law reforms and successfully lobbied Parliament to enact three new statutes for the preservation of endangered wild birds that gave priority to the scientific value of rare species. The account of Newton’s campaign presented in this article helps to locate Newton in (...) the nineteenth century conservation movement, while also shining a side light on the relationship between conservation science and policy-making more generally, including the variety of voices and approaches taken to conservation in the UK and US. Today, as we pursue new regulatory responses to critical environmental issues, such as biodiversity loss and climate change, the history of Newton’s campaign offers an early example of a successful approach to science-based law reform. It also shows how some of the issues that Newton and his contemporaries confronted at the science-policy interface in the nineteenth century are enduring and remain relevant today, including debates about; the role of scientist-advocates in policy-making, the criteria that make science advice effective, and whether the “democratization” of science leads to better policy decisions. (shrink)