Alfred Russel Wallace (1823-1913), a British naturalist, was best known for his development of a theory of evolution based on natural selection, contemporaneously with the British naturalist Charles Darwin.
In 1848 he made an expedition to the Amazon River with the British naturalist Henry Walter Bates, and from 1854 to 1862 he conducted research in the islands of Malaysia. During the latter expedition he noted fundamental zoological differences between the animal species of Asia and those of Australia, and he placed the zoological dividing line--known as Wallace's Line--between the Malay islands of Borneo and Celebes.
In the course of this research Wallace formulated his theory of natural selection; a striking coincidence was revealed in 1858 when he communicated his ideas to Darwin, whose own similar theory of evolution was then in manuscript. Excerpts from the manuscripts of both scientists were issued in a joint publication in July 1858, and Wallace's contribution was titled "On the Tendency of Varieties to Depart Indefinitely from the Original Type." His works include On the Law that has Regulated the Introduction of New Species* (1855), Malay Archipelago (1869), Contributions to the Theory of Natural Selection (1870), The Geographical Distribution of Animals (1876), and Man's Place in the Universe (1903).
*an actual link.
http://library.thinkquest.org/19926/java/library/bios.htm | 
