Charles Darwin. Computercoloured portrait of Charles Darwin (180982), British naturalist. Darwin originally trained in medicine, then the clergy. In these latter studies he became interested in natural history. He was eventually appointed as naturalist on HMS Beagle for its voyage to South America and the Pacific. This sailed in 1831, and provided much of the field work upon which Darwin was to base his famous book: On the Origin of Species by Means of Natural Selection, published in 1859. This work proposed evolution and species variation to be a response to environmental pressures, and revolutionised biological thinking.