Nobel Prize winners, scientific geniuses in their own fields, have scientifically questionable views in other fields. Alfred Russel Wallace, codiscoverer of the theory of natural selection, advocated spiritualism and believed that nonmaterial forces explained the evolution of the human mind. Percival Lowell, a pioneer in planetary astronomy whose observations paved the way for the discovery of Pluto, was convinced that he had discovered martian canals of intelligent origin.