The horse can be traced back over 50 million years. The horse started out as an animal called the Eohippus (meaning dawn horse), pictured below.


As you can see, they were the size of a large dog with four toes and lived in the forest, feeding on soft leaves.




25 million years later, the horse had developed into the larger Mesohippus (meaning half or middle horse). They were larger in size and lost a toe along the way! Their teeth had grown and they had developed an extra grinding tooth, so they could munch on the smaller, harder twigs and fruit they now ate.




Five million years later, the earth was changing very quickly. The climate changed and so did the land - the forests started to disappear and made way for open, grassy plains.


The horse evolved into the Merychippus, which survived on the shorter grass of the plains. Their teeth became stronger and better at grinding the tough grass. Their legs became longer and the middle toe developed into a hoof. This meant they could run much faster to escape predators.

Their eyes were wider apart than the earlier horses, so that they could keep a lookout for danger more easily.




Several different groups of horse descended from Merychippus, one of which was Pliohippus, which is thought to be the direct ancestor of the modern horse.


Horses had to become faster to escape their predators on the open plains so their bodies developed and their legs became longer. As you can see, Pliohippus had only one hoofed toe, and looked very similar to the horses we have today.




Modern horses belong to a group known as Equus and there are many species within this group, ranging from zebras and donkeys to ponies and racehorses.


If you read about the different parts of the horse's body you will learn how they developed into what they are now and why they are so well-suited to racing.