Evolutionary theory, which gave rise to a new discipline named Darwinian medicine, has had a major impact on modern medical research and practice. This paper focuses on phenomena such as evolved host defences, evolution of virulence, genetic conflicts with other organisms, adaptations to novel environments, and tradeoffs and constraints in biological systems. Charles Darwin enrolled as a medical student at the University of Edinburgh in 1825. (1) Disturbed by operating theatre scenes, he left medicine and Edinburgh, and in 1827 was studying in Cambridge to become a pastor. Darwin subsequently revolutionised the science of biology with his theory of evolution by natural selection, and deeply influenced biology, many other disciplines, cultural values and society in general. (2) Medical science, however, has recognised the significance of Darwinian theory only recently. In 1991, the psychiatrist Randolph Nesse and the evolutionary biologist George Williams (3) explicated the principles now know as Darwinian, or evolutionary, medicine. Thus, nearly 110 years after his death, Darwin was eponymously re-united with the discipline which he had left as a student before returning to it as a hierophant.