Indo-Australian insular elephants.

Abstract

Various Pleistocene dwarfed elephants known from the islands of Celebes, Flores and Timor in the eastern part of the Malay Archipelago are described and their relationships considered. It is evident that these pygmy forms arose independently on each of the islands as a result of isolation and genetic drift favouring small size as in the better-known cases of the Mediterranean and Santa Barbara Channel Islands dwarf species. The dispersal possibilities of elephants are discussed; the conclusion must be drawn that geographic spacing has been the prime factor in species formation. Idle or fruitless speculations about ecological or other non-morphological species criteria have been omitted; the taxonomy of proboscideans as far as needed in the present context is however elucidated. It is pointed out that wherever we find pygmy elephants we have also giant rodents; in these presumably small isolated populations giganticism in small rodents appears to have been as advantageous to the animals as is dwarfing in elephants. As neither the exact date of colonization nor that of the eventual extinction (brought about by man or otherwise) is known, we have no means of knowing how many generations were involved; it is, however, likely that evolutionary velocity has been higher under these conditions than is usual.