Charles Darwin's The Origin of Species (publ. 1859) is a pivotal work in scientific literature and arguably the pivotal work in evolutionary biology. The book's full title is On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. It introduced the theory that populations evolve over the course of generations through a process of natural selection. It was controversial because it contradicted religious beliefs which underlay the then current theories of biology. Darwin's book was the culmination of evidence he had accumulated on the voyage of the Beagle in the 1830s and added to through continuing investigations and experiments since his return. (Summary from Wikipedia)