Why did Charles Darwin begin thinking about Earth’s deep history?

Charles Darwin’s interest in Earth’s deep history was significantly shaped by his exposure to the work of the geologist Charles Lyell. Before embarking on his voyage aboard the HMS Beagle in 1831, Darwin was gifted the first volume of Lyell’s seminal work, Principles of Geology, by the ship's captain, Robert Fitzroy.1

Lyell’s writing introduced Darwin to the concept of uniformitarianism, which proposed that geologic time is virtually limitless and that significant changes in the natural world are the result of minute, incremental processes occurring over vast periods. Darwin later applied these principles to his own research, borrowing the idea that a sequence of small changes integrated over long durations could produce the remarkable transformations observed in living organisms. This intellectual foundation was essential to his development of the theory of evolution by natural selection.23