Hyracotherium, the oldest known ancestor of all modern horses, was only about 8 inches (20 cm) high at the shoulder.

Other species of wild horses were once indigenous to North America, populating the continent before and during the Ice Age. Approximately 10,000 years ago, horses in the Western Hemisphere migrated to Eurasia across the Bering land bridge and fanned out from Siberia to the rest of asia, Europe, and the Middle East.

The Wild Horse (Equus ferus) is a member of the Horse genus and was found in Europe and Asia. Two species or subspecies (taxonomy is debated) survived into modern times: The Tarpan or Eurasian Wild Horse (Equus ferus ferus), and the Przewalski's Horse or Mongolian Wild Horse (classification disputed, either Equus ferus przewalskii or Equus przewalskii).