Charles Darwin - Theory of Natural Selection
The Origin of Species by means of Natural Selection
After returning to England in 1836, Charles Darwin began recording his ideas about changeability of species in his Notebooks on the Transmutation of Species. Darwin’s explanation for how organisms evolved was brought into sharp focus after he read An Essay on the Principle of Population (1798), by the British economist Thomas Robert Malthus, who explained how human populations remain in balance. Malthus argued that any increase in the availability of food for basic human survival could not match the geometrical rate of population growth. The latter, therefore, had to be checked by natural limitations such as famine and disease, or by social actions such as war.
Darwin immediately applied Malthus’s argument to animals and plants, and by 1838 he had arrived at a sketch of a theory of evolution through natural selection (see Species and Speciation). For the next two decades he worked on his theory and other natural history projects. (Darwin was independently wealthy and never had to earn an income.) In 1839 he married his first cousin, Emma Wedgwood, and soon after, moved to a small estate, Down House, outside London. There he and his wife had ten children, three of whom died in infancy.
Darwin’s theory was first announced in 1858 in a paper presented at the same time as one by Alfred Russel Wallace, a young naturalist who had come independently to the theory of natural selection. Darwin’s complete theory was published in 1859, in On the Origin of Species. Often referred to as the “book that shook the world,” the Origin sold out on the first day of publication and subsequently went through six editions.