The Siberian Northeast shows striking parallels between the cosmologies of hunters and reindeer herders. What may this tell us about the transformation from hunting to pastoralism? This article argues for a structural identity between hunting and sacrifice, and for the domestication of the reindeer as the result of hunters’ efforts to use sacrifice to control the accidental variables of the hunt. Hunters can practise their ethos of ‘trust’ with prey only through highly controlled ritual enactments. We describe two: the famous bear festival of the Amur Gulf region and the consecrated reindeer of the Eveny. Both express the same overall logic by which sacrifice functions as an ideal hunt. The animal is involved in a relation not of domination but of trust, while also undergoing a process of taming. We therefore suggest that the origin of the reindeer’s domestication may be found not primarily in patterns of ecological or economic adaptations, but rather in cosmology.