The publication of Darwin's theory brought into the open Charles Darwin's theory of evolution through natural selection, the culmination of more than twenty years of work. Thoughts on the possibility of transmutation of species which he recorded in 1836 towards the end of his five-year voyage on the Beagle were followed on his return by findings and work which led him to conceive of his theory in September 1838. He gave priority to his career as a geologist whose observations and theories supported Charles Lyell's uniformitarian ideas, and to publication of the findings from the voyage as well as his journal of the voyage, but he discussed his evolutionary ideas with several naturalists and carried out extensive research on his "hobby" of evolutionary work.