The evolution of horses has been well studied.
Fifty million years ago, there were no horses as we know them now.
Of the earliest fossil horse, the North American one is called Eohippus, and the Eurasian one is called Hyracotherium.
Both were small animals: Eohippus was the larger of the two at twice the size of a terrier dog.

Many changes took place between those little animals and today's horse.
These changes are best explained as adaptations to its changing ecological niche.
From a small forest-dweller eating nuts and fruit to a larger forest browser eating leaves and small branches.
Finally, the modern horse is a grazer on open grassland, with different teeth, legs for running and much larger size.
Major changes happened in the mid-Miocene when the climate became cooler, and grassland began to replace forests.
This change continued, and several groups of mammals changed from browsers to grazers.
The evolution of horses has been well studied. Fifty million years ago, there were no horses as we know them now. Of the earliest fossil horse, the North American one is called Eohippus, and the Eurasian one is called Hyracotherium. Both were small animals: Eohippus was the larger of the two at twice the size of a terrier dog.
Many changes took place between those little animals and today's horse. These changes are best explained as adaptations to its changing ecological niche. From a small forest-dweller eating nuts and fruit to a larger forest browser eating leaves and small branches. Finally, the modern horse is a grazer on open grassland, with different teeth, legs for running and much larger size. Major changes happened in the mid-Miocene when the climate became cooler, and grassland began to replace forests. This change continued, and several groups of mammals changed from browsers to grazers.
Horse