This paper contends that understandings of race and practices of racial differentiation underwent a significant epistemological shift around the first decades of the twentieth century. It reaches this conclusion via consideration of a dog breeding programme conducted by the statistician and hereditarian theorist Karl Pearson. In 1913, Pearson proclaimed that he, along with his collaborators Edward Nettleship and Charles Usher, had created a ‘new race’ of dog. Notable for its complete absence of hair pigmentation, this race appeared to demonstrate the potential that experimental animal breeding had for imperial policy-making. In differentiating his dogs from the Pekingese spaniels from which they had been produced, Pearson sought to show that 'foreign' animals could be made to approximate British racial standards. In Pearson's wake, animal breeding became an increasingly persuasive means by which scientists sought to legitimate racial contentions. By the 1920s, established anthropocentric approaches to human differentiation had begun to be replaced by new, animal-centred techniques and practices. Whereas nineteenth century conceptions of race had primarily been articulated in relation to the study of human bodies, in the new race of the twentieth century differentiation would involve study of and experimentation with bodies of all kinds – animal and human.