Charles Darwin. Coloured historical portrait of Charles Darwin (1809-1882), British naturalist, in his early 20s. Darwin studied medicine and theol- ogy, but his real interest was in natural history. In 1831, he joined the HMS Beagle as a naturalist on a five-year voyage around the world. This prov- ided the data for his revolutionary book, On the Origin of Species by Means of Natural Selection (1859). In this work, he suggested that natural variation in a species creates a variety of indiv- idual traits, some more useful than others. Compe- tition causes favourable traits to survive and so a species evolves. His ideas were opposed by the Church, but have now largely been accepted.