Building on the innovative work of James Hutton and his follower John Playfair, Lyell favoured an indefinitely long age for the Earth, despite evidence suggesting an old but finite age. He was a close friend of Charles Darwin, and contributed significantly to Darwin's thinking on the processes involved in evolution. As Darwin wrote in On the Origin of Species, "He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science, yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume." Lyell helped to arrange the simultaneous publication in 1858 of papers by Darwin and Alfred Russel Wallace on natural selection, despite his personal religious qualms about the theory. He later published evidence from geology of the time man had existed on Earth.