Elephant Evolution in Action
The evolution of elephants and related forms, collectively known as the proboscideans, is one of the better-recorded tales of mammalian evolution. Since its origin in the late Paleocene Epoch, about 60 million years (My) ago, the order Proboscidea witnessed a spectacular radiation until the end of the Pleistocene Epoch, about 10,000 years ago. The evolutionary course of the proboscideans, marked by an overall increase in body size, also took many seemingly bizarre paths, including extreme dwarfism and morphologies (seen from the fossil record) that only the most daring paleontologist could have otherwise imagined (fig. 1.1). There are many examples of parallel and convergent evolution. During this period, the proboscideans occupied almost every continental habitat type, including swamps, tundra, boreal forests, deserts, savannas, tropical forests, river basins, and high mountains. With the exception of Australia and Antarctica, fossil proboscideans have been found in every continent. Adaptations in anatomy and physiology of the proboscideans were obviously as diverse as the spread of habitats they occupied.
Interest in the story of elephant evolution is probably rivaled only by that of human evolution (and perhaps dinosaur extinctions). One reason is obviously our fascination with creatures larger than we are ourselves. In addition, the bones of large animals are more likely to be preserved and hence discovered and described in greater detail. The largest land mammal ever known is actually not a proboscidean. This was the giant “giraffe rhinoceros” or Indricoth-