Wallace Line to the west of the Philippines. Wallace's studies in Indonesia demonstrated the emerging theory of evolution, at about the same time as Joseph Dalton Hooker and Asa Gray published essays also supporting Darwin's hypothesis. Understanding of the biogeography of the region centers on the relationship of ancient sea levels to the continental shelves. Wallace's Line is visible geographically when the continental shelf contours are examined; it can be seen as a deep-water channel that marks the southeastern edge of the Sunda Shelf which links Borneo, Bali, Java, and Sumatra underwater to the mainland of southeastern Asia. Australia is likewise connected
Wallace Line Lombok Strait between Bali and Lombok. The distance between Bali and Lombok is small, about . The distributions of many bird species observe the line, since many birds do not cross even the shortest stretches of open ocean water. Some bats have distributions that cross the line, but larger terrestrial mammals are generally limited to one side or the other; exceptions include macaques, pigs and tarsiers on Sulawesi. Other groups of plants and animals show differing patterns, but the overall pattern is striking and reasonably consistent. Flora do not follow the Wallace Line to the same extent as fauna. One