History of the Horse
To go back to the very beginning of the history of the horse we must try to imagine a small animal, about the size of a fox, that lived some 50 to 60 million years ago during the Eocene period. We call that ancient ancestor of the horse Hyracotherium. Although it did faintly resemble the horse as we know it today, Hyracotherium had four toes on its front feet and three toes on its hind feet. This is particularly interesting in view of the fact that the Tapir (a relative of the horse) still has this arrangement of toes.
Hyracotherium lived and browsed in the forests of what we would now call Europe and Asia. Meanwhile in another part of the world which we now know as America - but which was at that time still connected to the main land mass of Asia - another and rather similar animal was developing. This animal, also small, a forest dweller and eater of leaves, we call Eohippus (or dawn horse).
Some 30 million years after the appearance of Eohippus a new horse-like animal appeared. It was larger than Eohippus (about the size of a lamb) and had only three toes, with the middle toe beginning to evolve into the main support for the foot. This animal, Mesohippus had stronger teeth than Eohippus and it was able to eat both leaves and grass. In the millions of years that followed, these prototype horses were followed by Merychippus and Pliohippus, both bigger and better models. Pliohippus evolved about 12 to 13 million years ago and it had single toes or hooves and ate grass. The scientific Order to which the horses belong is known as Perissodactyla, which means quite simply 'one toe’.
Today, the Family Equidae includes all the surviving horse-like animals (horses, asses and zebras). There is only one true species of wild horse remaining in the world today - the Przewalskis' or Mongolian wild horse.
By the time humans arrived on Earth some 5 to 6 million years ago, the horse was already firmly established - having arrived some 50 million years earlier!
Read More: What do Horses Eat?