Wallace, Alfred Russel (1823–1913), a British naturalist. He shares credit with Charles Darwin for developing the modern theory of evolution. Others had developed theories of evolution, but these theories, without supporting scientific evidence, found little acceptance. Wallace and Darwin were the first to present a theory based on carefully gathered evidence from nature.

Wallace's studies in the East Indies of various forms of life led him to formulate his ideas on evolution. He sent an essay on the subject to Darwin, who had formulated similar ideas. In 1858, Darwin publicly presented his and Wallace's papers on evolution at a meeting of the Linnaean Society of London.

Wallace also studied the geographical distribution of plants and animals. He discovered the boundary that separates distinctly Asian animals from distinctly Australian ones. He believed that this boundary, later known as Wallace's Line, existed because Australia and nearby islands had split off from Asia at some time in the past and the animals had then evolved in different ways.

Wallace was born in western England. An interest in insects led him to travel in the Amazon valley of South America, 1848–52. Wallace's travels in the East Indies lasted from 1854 to 1862, and he returned with 125,660 specimens of wildlife. The Malay Archipelago (1867) is his report of the trip.