Where did horses come from? It took over 50 million years for this large mammal to evolve into what it is today and believe it or not, horses were once small, woodland mammals about the size of a house cat!
It is believed that these early horses share commonalities with other hoofed mammals such as tapirs and rhinoceroses. As time passed, and the world's vegetation began to evolve, so did the early horses. In looking at these characteristics in evolution, it will be interesting to think about what a future "horse" may look like.
Eohippus was one of the earliest horse relatives, dating back 52 million years ago. This was a relatively short animal which measured only 10 - 17 inches in height with a small, short head and an arched back which is similar looking to a modern donkey. Eohippus was grazing mammal with dull teeth that were primarily used for eating fruit and other soft foliage.
Their long legs were adapted for running, but their feet were soft and padded like a dog's paw and had a small hoof in place of claws.
The Eohippus thrived for approximately 20 million years and in that time their teeth had evolved to reflect a change in diet from mainly fruit to grasses. This early horse eventually evolved into many other varieties of prehistoric equines.
Orohippus was an early evolution from the Eohippus which thrived approximately 50 million years ago. It was similar to the Eohippus but had a smaller body, limbs, longer legs, more of an elongated head and was thought to be an excellent jumper. The largest difference was in its teeth where the molars became more specialized to grind harder plant material.
Mesohippus roamed what we now know as North America approximately 30 million years ago. The continent began to dry and early forms of grass evolved to what resembles a plain or prairie. These early Equidae evolved to adapt to the changing environment by developing tougher teeth for the new grasses, became larger in size, and had longer legs which allowed them to run swiftly in open areas.
The Mesohippus was larger than its earlier relatives and measured about 24 inches tall. Its back was straighter and its face, snout and neck were slightly longer than a Eohippus.
Miohippus is also known as the "lesser horse" and lived approximately 36 million years ago. The population split from the Mesohipus groups which they coexisted with for millions of years and eventually replaced the Mesohippus all together.
The Miohippus was much larger than its predecessors, had new ankle joints, and had teeth that have a crest which resembles a modern horses.
Miohippus continued to thrive to approximately 5 million years ago where it diversified into two major Equidae groups: one which adapted for living in the forests, and the other that adapted to prairie life.
Prehistoric horse bones have been found in Canada which date back 12,000 years. For reasons that are still in question, there was a mass extinction of North American mammalian populations which ended all early horse existence on this continent. It was not until 1493 when Iberian horses came to the Americas with Columbus, when horses began to once again, graze upon North American grasses.