George C. Williams (biologist) should only be used where it is really necessary", and, that, when it is necessary, selection among genes or individuals would in general be the preferable explanation for it. He elaborated this view in later books and papers, which contributed to the development of a gene-centered view of evolution; Richard Dawkins built on Williams' ideas in this area in the book "The Selfish Gene". Williams was also well known for his work on the evolution of sex, and was an advocate of evolutionary medicine. In later books, including "Natural Selection: Domains, Levels and Challenges", Williams softened his views on group
Alternatives to evolution by natural selection Alternatives to evolution by natural selection Alternatives to evolution by natural selection, also described as non-Darwinian mechanisms of evolution, have been proposed by scholars investigating biology since classical times to explain signs of evolution and the relatedness of different groups of living things. The alternatives in question do not encompass religious points of view such as young or old earth creationism or intelligent design, but are limited to explanations proposed by biologists, though one was confusingly named 'theistic evolution' by Asa Gray. Where the fact of evolutionary change was accepted but the mechanism proposed by Charles Darwin, natural selection, was