This map, published in Wallace's book describing his travels in the Malay Archipelago, shows the routes he took around the region while he was visiting the islands and collecting specimens there between 1854 and 1862. His occupation during these years was collecting natural history specimens for sale, but he also made detailed observations of the plants, animals, land, and people there, which made him a foremost expert on the region at the time. Wallace’s work on both evolution and biogeography was based on his detailed observation of species during his travels on the routes shown on this map. While at Sarawak in 1855, he wrote a paper “On the Law which has Regulated the Introduction of New Species,” which proposed the following law: “Every species has come into existence coincident both in time and space with a pre–existing closely allied species.” This proto-evolutionary statement was his explanation for why similar species were endemic to adjacent areas, and was a direct response to diverse groups of species that he found concentrated in the Malay Archipelago. He wrote the paper which earned him the title of co-discoverer of evolution by natural selection on the island of “Jilolo” in 1858. Titled “On the Tendency of Varieties to depart indefinitely from the Original Type,” this paper describes the struggle for existence between varieties within a species leading to divergent evolution as better-adapted varieties survive more to reproduce. Wallace famously wrote this paper while suffering from a tropical fever, and his discussion of varieties of species and the pressures to which they are subject was surely grounded in his observation of the lifeforms around him there. This map gives a sense of how extensive Wallace’s travels in the Malay Archipelago were and the number of distinct biotas from different islands he was able to observe as he developed his theories.
