The Origin of Species is the magnum opus of natural scientist Charles Darwin. In the book Darwin presents the theory that populations evolve over the course of generations through the process of natural selection. The book goes on to present a body of evidence for the hypothesis that the diversity of life in this way arose by common descent through a branching pattern of evolution. Darwin gathered much of his evidence for the book on the Beagle expedition in the 1830s to among other places the Galápagos Islands.