II.

Evolution

The earliest known ancestors of modern-day elephants evolved about 65 million years ago in the region now known as Egypt. Called Moeritherium, these swamp-dwelling animals were from pig- to cow-sized, with an elongated snout but no trunk. They sported two pairs of slightly elongated front teeth—indicators of what would eventually evolve into tusks. Three groups of elephant-like animals descended from Moeritherium: Deinotherioidea, Mastodontoidea, and Elephantoidea. Deinotherioidea evolved from 54 million to 38 million years ago and lived in parts of Asia, Europe, and Africa. It possessed a trunk and two tusks, which pointed backward, possibly for hoeing up food from the edges and bottoms of swamps. The last surviving members of this group died out about 10,000 years ago.

The earliest members of the Mastodontoidea group evolved about 38 million years ago. These animals had elephant-like trunks, and, depending on the family, displayed either two or four tusks. The upper tusks were vertical, or upward pointing. The lower set, when present, bent forward and were sometimes shaped like shovels, apparently for digging plant roots and bulbs. The mastodon, the most familiar member of this group, evolved about 15 million years ago, and spread to Europe, Asia, Africa, and North America. Its descendants lived in the cold world of the last great Ice Age—2.5 million to 8,000 years ago, when thick glaciers covered parts of North America and Europe. The mastodon had two tusks that curved upward and was covered with a thick coat of shaggy hair. About 10,000 years ago, early humans began hunting mastodons, contributing to their extinction.

The Elephantoidea group, which evolved 8 million to 10 million years ago, includes the mammoth and Stegolophodon. The mammoth also lived during the Ice Age and was covered with a thick, woolly coat. Unlike the mastodon’s forward-curving tusks, the mammoth’s tusks curved backward. The mammoth displayed a prominent hump on its back. Mammoths roamed North America, Africa, Europe, and Asia, were hunted by early humans, and died out about 8,000 years ago. Stegolophodon evolved about the same time as the mammoth and inhabited Europe, Asia, and Africa. Its tusks and other features were intermediate between the mammoth and modern-day elephants. Stegolophodon’s descendants are the African and Asian elephants of today.