The Evolution of Horses

Imagine a world in which horses of all colours, shapes and sizes roamed the world, some barely larger than a small dog. That world no longer exists—but once it was real. Today's horses represent just one tiny twig on an immense family tree that spans millions of years. All the other branches of the horse family, known as Equidae, are now extinct. The earliest known horses evolved 55 million years ago and for much of this time, multiple horse species lived at the same time, often side by side.

Ancient Horses

Some 10 million years ago, up to a dozen species of horse roamed the Great Plains of North America. They came in many shapes and sizes. Some lived in the forest, others on open grassland.

Here, two large Dinohippus horses graze on grass, much like horses today. But a three-toed Hypohippus tiptoes through the forest, nibbling on leaves. A small, three-toed Nannippus, which ate both grass and leaves, is eating shrubs here.