He spent eight years in the Malay Archipelago collecting and cataloguing over 120,000 specimens, recording data and making breathtaking illustrations. In addition to arguing for the idea of species change, he noticed that certain groups of creatures were geographically distributed in discrete areas and times.
While in Southeast Asia, he found islands with their own unique species. But more famously, he discovered strikingly different birds and animals when he crossed the deep and narrow channel separating the islands of Bali and Lombok. This led to his conclusion that this must be a boundary between two major zoological realms: to the one side, the animals were typical of Asia, on the other of Australasia. In 1859, Wallace demarcated the 'Wallace Line,' a faunal boundary between Australia and southeast Asia.
Quite independent of Charles Darwin, he also discovered natural selection and sent Darwin his paper in which he explained that, "The life of wild animals is a struggle for existence and the weakest and least perfectly organised must always succumb..." in March 1858, prior to Darwin's famous publication, 'On the Origin of Species.' in 1859. Wallace, who came from a humble background and was self-taught, was pleased to have been accepted in the scientific establishment and was happy for Darwin, who had spent 20 years developing his theory, to bask in the glory.
Comprising parts of Sundaland, the central islands of Indonesia - between Java, Bali and Kalimantan (Borneo) on the west and Papua at the eastern end of the country - is a living laboratory for the study of evolution. It has been named Wallacea in Wallace's honour. Wallacea is home to 697 bird species, of which 249 are endemic.