The British naturalist Charles Darwin returns to Falmouth, England, aboard the HMS Beagle, ending a five-year surveying expedition of the southern Atlantic and Pacific oceans. Visiting such diverse places as Brazil, the Galapagos Islands, and New Zealand, Darwin acquired an intimate knowledge of the flora, fauna, and geology of many lands. This information proved invaluable in the development of his theory of evolution, first put forth in his groundbreaking scientific work of 1859, The Origin of Species by Means of Natural Selection. Darwin's theory argued that organisms gradually evolve through a process he called "natural selection." In this process, organisms with genetic variations that suit their environment tend to propagate more descendants than organisms of the same species that lack the variation, thus influencing the overall genetic makeup of the species. His Origin of Species, the first significant work on the theory of evolution, was greeted with great interest in the scientific world but was attacked by religious leaders for its contradiction of the biblical account of creation.