The first elephants to walk the Earth lived in the Eocene times some 60 million years ago.The earliest known fossils, discovered in Egypt, are of a creature called Moeritherium. In general appearance this creature was nothing like a modern elephant. It was only about 2 feet high and had no trunk. However, the structure of the skull and the form of the teeth show that it was a very primitive kind of elephant. From ancestors similar to this, arose the whole range of living and extinct elephants, a total of about 350 species.
Out of the vast number of elephants and near-elephants that have existed, only 2 species are alive today. These are the African Elephant (Loxodonta africana) and the Indian or Asiatic Elephant (Elephas maximus), which differ in a number of details.
The most obvious thing about elephants is their size: A fully grown African specimen may be more than 11 feet high at the shoulder and may weigh 7 tons. The Indian elephant is usually slightly smaller and there are sub-species such as the African forest elephant only about 18 feet tall. Elephants are by far the largest of land-living animals. The giraffes top them in height only by virtue of their long slender necks.
To support their great weight the elephants have huge columnar legs which give them a very clumsy appearance. Nevertheless, an elephant can move along at a fair speed - and silently. A cushion of tissue under the foot effectively silences the foot-steps. Although elephants can be trained to get up on their hind legs, they cannot jump at all, their leg structure is not suitable.
The skull is large but relatively light. The bones are full cavities and channels (sinuses) which contain air. Without these cavities, the animal would be unable to lift his head. The brain is large although not large in proportion to the size of the body. The elephant is an intelligent beast whose memory is a well-known feature. The senses of smell and hearing are well developed.
An elephant's trunk acts as another limb, and a very useful at that. It enables the elephant to get food from the ground and from high in the tree and is also used in drinking - water is sucked into the trunk and then squirted into the mouth. The trunk consists of many bands of muscles and it can be shortened, stretched or curved in any direction. It is extremely sensitive to touch, especially at the tip.
Elephants are vegetarians and a full-grown needs a lot of daily food supplies. It is little wonder that they destroy their habitats when large numbers are concentrated in small areas. An elephant's digestion is not very good, however, for the feces contain a lot of unaltered plant material. This is in spite of the huge grinding surface of the cheek teeth.
There is only one fully-functional cheek tooth in each half of each jaw at any one time. This is made up of plates of enamel and dentine which stand up as ridges above the cement to make the grinding surfaces. As each tooth wears down it is replaced by another growing from behind it. The old tooth is gradually resorbed into the body and the last remains fall out. During its life the elephant grows only 24 cheek teeth - six in each half of each jaw. When the last teeth are worn down the animal will die of starvation for it cannot feed. Most elephants probably die of other causes, however, before this stage is reached. In the wild, 50 years is a good age for an elephant.