|Charles Darwin became interested in the study of evolution when he was official naturalist on the HMS Beagle, which sailed around the world from 1831 to 1836. After his return, he continued his research on animal and plant forms, concluding that selection was the key to man's success. His theory of evolution, soon known as Darwinism, stated that beneficial variations of species were preserved, while others, unfavored by their environments, were eliminated in the struggle for existence. Later his discoveries were corroborated by Mendelian genetics and became the prime cornerstone of modern scientific teaching. Always poor in health, he spent the last 40 years of his life studying and writing at his home in Down, Sussex. Darwin had the faculty of writing simply on abstruse matters; his use of reminiscence or a discursive anecdote lending great color to his scientific expositions.