How Horses Evolved

           It took about 55 million years for the Equus Family (see the "Some Information" section) to evolve from their earliest horse-like ancestor, which lived during the Eocene period. That animal, though first called Eohippus, is now named Hyractotherium. It was not much larger than a hare. It was a "browsing" animal - unlike the today's horses, it was feeding on leaves and shrubs. Also, it had paw-like feet with four-toed forefeet, and three-toed hind feet. What is a horse's hoof? It's a toe which is what we call a "hoof" nowadays, but it used to be three - the middle one, and the other two grown into the leg. So the Hyractotherium's feet reminded that of a rodent, and its low-crowned teeth were made for "browsing". The Hyractotherium is believed to have an appearance of a big guinea pig with a donkey's tail, and stripes along its back.   

           Then the Hyractotherium evolved into the Mesohippus. It was much the same, except it had three-toed feet, no stripes, and its teeth were suited slightly more for grazing. It was about the size of a sheep, and it had lived during the Oligocene period about 37 million years ago.

            The next horse was Parahippus. It hadn't changed much in any way, except for the two side toes of each foot growing deeper into the leg, and the horse growing larger.

             But then came the Miocene period (about 20 million years ago) and many of the woodlands became grasslands. Adapting to this environmental change, the horses had developed longer legs in order to run across a large area in search of pasture and to escape from predators. Furthermore, their teeth became high-crowned in order to adapt to the new diet. The first grazing horse was the Merrychippus, which then became the Pliohippus - the first one-toed horse. After that, came the Pleistocene period (about two million years ago), which gave rise to the Equus - the nowadays horse.