Steps on the path to the origin of species

The choice of Charles Darwin to serve as geologist on H.M.S. Beagle came about in a somewhat haphazard fashion, and by modern standards his technical qualifications for the post were not strong. However, during the voyage he was exposed to a wider range of phenomena, both in geology and in natural history, than any previous scientist, and his innate qualities of enquiring critically with an open mind into the why and wherefore of every one of his observations enabled him to make very effective use of his experience. By the end of the voyage he had found himself ready to abandon the doctrine of the fixity of species, and a few months later he opened the first of the series of notebooks on "Transmutation of Species" in which he recorded his private thinking. He quite quickly arrived at the Principle of Natural Selection as a mechanism for the creation of new species, but the process of building up adequate evidence in support of his theory was a slow one, and more than 20 years had passed before his great work was finally ready for publication.