A Day in the Life
Though Darwin was often ill during the years at Down House, he produced an immense amount of work. He wrote more than 16 books, on subjects ranging from climbing plants to earthworms, and innumerable papers. He maintained this pace partly by limiting interruptions and keeping to a strict routine. Darwin's wife, Emma, did her part: As one son recalled, she "shielded him from every avoidable annoyance."
At Down, life had a predictable pattern. Darwin rose early and walked in the garden before breakfast. He worked until 9:30, when he spent an hour in the drawing room, listening to family letters being read. He resumed work in the study, then at noon walked, rain or shine, around the Sandwalk. Afternoons Darwin generally devoted to maintaining his vast correspondence and to reading. "My life goes on like clockwork," he wrote, "and I am fixed on the spot where I shall end it."
Natural selection, as Darwin explained in the Origin of Species, involves a struggle for survival. Any trait that gives an organism a competitive edge would tend to spread in future generations. In the Descent of Man, Darwin proposed an additional evolutionary mechanism--sexual selection.
Consider birds, Darwin suggested. Couldn't females have a standard of beauty that would lead them to select, "during thousands of generations, the most melodious or beautiful males"? If so, that would account for the beautiful but clumsy tail of a peacock, and the vivid, look-at-me color of a male cardinal, both of which seem to make males more vulnerable to predators. If females chose males with the longest tails or the brightest colors, those males could have more offspring than their plainer brothers. Modern scientists agree with Darwin's insight: Sexual selection is a powerful evolutionary force.