- He coined the Wallace's line to describe the hypothetical line separating Asia and Australia which separated the two continents and the species found. It runs through the Borneo-Celebes strait, southeast of the Philippines and east of Bali. In the mid 20th Century, geological studies of plate tectonics showed there is an Indo-Australian plate that has Wallace's line as a border.
His studies of the Malay Archipelago led to him arrive independently at a theory of evolution similar to Charles Darwin's. Darwin at that time had not published his theory, but when Wallace sent him a memoir of his theories, asking him to forward it for publication, Charles Lyell and Joseph Hooker advised Darwin that he should publish his own thoughts at the same time. Darwin did this in a paper presented to the Linnean Society of London in 1858.