Based on discoveries widely supported through scientific studies of fossils, domestic horses, like most plant and animal species of today, are the result of a series of gradual changes throughout time. It has been concluded that ancestors of today’s horses appeared during “the Age of Mammals” also known as Cenozoic Age. In the following table there is a list of the most important species considered to be ancestors of the modern horses:
Note: The severe climatic conditions in North America during the Ice Age, about 10,000 years ago, dramatically diminished areas with grass, causing Equidae to become extinct on the American continent.
The current domestic horse breeds (Equus caballus), with 64 chromosomes, are the result of crossing, at minimum, three horse-type species of Family Equidae:
· The “Nordic” horse-type from Northwest Europe: This subspecies had the thickest body and leg bones and the biggest hooves and head. Additionally, because the horse used to live in very cold areas the coat became very thick. Abundant, long hair appeared on the fetlocks, which may also have covered the hooves. This is the origin of today’s “draft” horse breeds.
· The “Arab” horse-type from the Middle East: This subspecies had the most refined conformation with thin leg bones, high tail, and concave (known as “dished”) face. It was light and a very fast runner. This is the origin of the Arabian horse.
· The “Barb” horse-type from Southern Asia and Northern Africa: This subspecies was a little less refined than the “Arab” type, but still light and fast. It was very resistant to heat and unfavorable conditions. This produced the Barb horse breed. Many specimens of this breed were taken to Spain by the North African warriors (Moors) during the several invasions from the eighth to fifteenth centuries. Later, the Barb horse became the foundation of most horse breeds on the American Continent.
Other Equidae species from Central Europe, Western and Central Asia, the Middle East, and Northern Africa later produced asses; others from Eastern Asia produced Przewalski’s horses; and others from Africa produced zebras