Where Asia meets the Australian continental tectonic plate, there is a complex interchange of living species that is constantly occurring. In the far southeast, the Asian ecosystem meets Australia in a region of islands known to biogeographers as Wallacea.
Wallacea is named after the pioneering ecologist and geographer Alfred Russel Wallace (1823–1913), who was one of the most important scientists of our time. His observations of the zoological differences to the northwest and southeast of an imaginary line through the Indonesian island of Sulawesi, were part of a body of work that, alongside Charles Darwin, reinvented biology through the lens of evolution. We can follow his career to his co-authoring of the theory of evolution with Charles Darwin while he was working as a collector in Asia.
He identified a line running through the Makassar Strait, a deep stretch of water between the east coast of Borneo and the western coast of Sulawesi (then known as Celebes), as a significant barrier that distinguished animal species on both sides. To the west in Bali, Borneo, Java and the Asian mainland were monkeys, apes, rhinoceros, squirrels, tigers, and hornbills. To the east in Lombok, Sulawesi, Timor and the Australian mainland were tree kangaroos, cockatoos and honeyeaters.