Major inconsistencies in Darwin's theory of the origin of species by natural selection remained unresolved for over a century until the results of recent research in various genome projects led to the theory's reinterpretation. Reviewing this new information, Donald Forsdyke, a laboratory scientist involved in genome research, wondered whether similar discoveries could have been made a century earlier, by one of Darwin's contemporaries. "The Origin of Species Revisited" describes his investigation into the history of evolutionary biology and its startling conclusion. The trail led first to Joseph Hooker and Thomas Huxley, who had been both the theory's strongest supporters and its most penetrating critics, and eventually to the Victorian George Romanes and Darwin's young research associate William Bateson. Although these men were well-known, their resolution of the origin of species paradox has either been ignored (Romanes), or ignored and reviled (Bateson).Four years after Darwin's death, Romanes published a theory of the origin of species by means of 'physiological selection' that resolved the inconsistencies in Darwin's theory and introduced the idea of a 'peculiarity' of the reproductive system that allowed selective fertility between 'physiological complements'. Forsdyke argues that the chemical basis of the origin of species by physiological selection is actually the species-dependent component of the base composition of DNA, showing that Romanes thus anticipated modern biochemistry. Using this new perspective Forsdyke considers some of the outstanding problems in biology and medicine, including the question of how 'self' is distinguished from 'not-self' by members of different species. Finally he examines the political and ideological forces that led to Romanes' contribution to evolutionary biology remaining unappreciated until now.