The scientific name of the modern horse of today is Equus caballus. This animal has been present on earth for about one million years. Its earliest ancestors however lived over 60 million years ago. There were numerous changes that occurred over this period of time that changed a small rodent-like creature into the stunning animal that it is today. The earliest fossils of the horse (termed eohippus, meaning dawn horse) were found in England in 1830. These fossils were of a small animal, only about 1 foot tall that had a sheep-like head and large hindquarters much like a jack rabbit. It also had 4 toes on each forelimb and 3 toes on each hind leg all of which were covered by a heavy hoof-like cuticle. These creatures had soft teeth and were quite prolific. These original fossils were so unlike modern horses that they were first incorrectly classified as rodents. Over the course of 30 million years the eohippus changed into what was called mesohippus. This animal was somewhat taller (about 2 feet) and had soft teeth because it lived in swampy conditions and ate leaves, bark, and tubers. Another change that occurred in this animal was that now there were only 3 toes on both fore and hind legs.
Great changes over the next 20 million years led to significant evolutionary changes in the horse as well. The next identified precursor to the modern horse was termed merychippus and this animal had hard teeth (due to changes in swamps into grasslands as the animal became a grazer). Additionally these animals now were beginning to show the single toe of the more modern horse with the side toes becoming vestigial (to become splint bones of the modern horse). During the great ice ages of about 5 million years ago the horse, as it was, became extinct in the northern hemisphere along with other prehistoric animals such as rhinoceros, camels, and mastodons. Fossils in Europe and Asia however have been found that indicate the evolution of merychippus into the modern horse of today.
Over the 60 million years, the greatest changes to occur were an increase in size, the change from soft to hard teeth and the loss of the number of toes from 4 to 1. Horses were domesticated in Europe and Asia around 500 BC and brought to the new world around 1500.
