Abstract
This chapter outlines the history of the "One Health" concept through a neutral, prospective, evidence-based approach that pays due regard to historical context. It focuses on the constellation of ideas, practices and circumstances that brought human and animal health (and to a lesser extent, the environment) into alignment, the people and institutions involved and the reasons for change over time. The first section analyzes intersections between human and animal health in the pre-modern era. It shows how deeply animals and animal health were embedded within human medicine and the importance of the environment to health ideas and practices. The second section extends from the late 18th-century foundation of the veterinary profession until the turn of the 20th century. It tracks the evolving relationship between the veterinary and medical professions, and how, as scientific ideas and practices changed, new links were forged between humans, animals and the environment. The third section extends this analysis into the 20th century, focusing particularly on the changing status of animals within medical research, and on international efforts to develop comparative medicine and veterinary public health. The conclusion reflects on the importance of these findings for history, and for "One Health" today.