Memorial plaque at Wreck Bay, San Cristobal Island, depicting a young Charles Darwin. Darwin studied medicine & theology but his interest was in natural history. He was a naturalist on a five year voyage around the world during 1831-36. This provided the data for his book, Origin of Species (1859). His theory of natural selection suggested that natural variation in a species creates a wide range of individual traits, some more useful than others. Competition to survive causes favorable traits to survive and so a species evolves. Though not the first person to suggest evolution, Darwin was the first to construct a proper scientific argument to prove it.