The first printing of Charles Darwin’s book, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, sold out in a matter of days. Darwin considered the volume a short abstract of the ideas he’d been developing about evolution by natural selection for decades. He’d been building on his ideas since his five-year journey in the 1830s to the South American coast, the Galapagos Islands, and other regions on the British ship H.M.S. Beagle. Darwin probably wouldn’t have published in 1859 if not spurred by Alfred Russel Wallace’s paper touching on the idea of natural selection. Wallace was a young naturalist who had developed his ideas while working in the islands of the Malay Archipelago.

Darwin’s exploratory survey on the H.M.S. Beagle had brought him into contact with a wide variety of living organisms and fossils. The adaptations he saw in the finches and tortoises on the Galapagos Islands struck him particularly acutely. Darwin concluded that species change through natural selection, or – to use Wallace’s phrase – through "the survival of the fittest" in a given environment.