The family evolved more than 50 million years ago, in the Eocene epoch, from a small, multi-toed ungulate into larger, single-toed animals.

The oldest known fossils assigned to Equidae were found in North America, and date from the early Eocene epoch, 54 million years ago.

[3] Later species reduced the number of toes, and developed teeth more suited for grinding up grasses and other tough plant food.

They have evolved specialized teeth that cut and shear tough plant matter to accommodate their fibrous diet.

The sole surviving genus, Equus, had evolved by the early Pleistocene epoch, and spread rapidly through the world.