Prehistory in North America:

Recorded history has been predominantly shared by man and his principal friend, ally and servant—the horse. Empires have been won, developed and lost on horseback, and the outstanding figures of action of each era were of necessity, horsemen.

 This close relationship of roan and horse began around one hundred and sixty million years ago in the geologic period known as the Jurassic, on the land mass that we know today as North America, with the emergence of the first furry warm-blooded animals, the first mammals. (Z, 24)* As the Jurassic period, the age of the great reptiles, drew to a close around seventy-five million years ago, mammals began to proliferate and differentiate, and the paths of man and horse diverged.

 As the mammalian tree of living things grew and formed, branching in the direction of most favorable growth and coming to a full stop in the face of insurmountable obstacles, an order of five-toed mammals from which the horse was eventually to spring developed. (Z,25) From this order, later named Condylarths, descended a group of browsers called Hyracotherium. (Z,25)

They were common during the Paleocene epoch, ending sixty million years ago, and their five toes had begun the process of becoming one hoof. Most Hyra- cotherium had four toes, the fifth having shrunk to a vestigial level, except for Eohippus, whose hind feet had only three usable toes. (Z,25) Eohippus had a small mouth showing only the beginnings of molars to come.

 

      By the Oligocene epoch, forty million years ago, man's close companion the horse had reached a stage known as the Mesohippus (Z,25), a sheep-sized forest browser with better developed jaws and higher crowned teeth. He had three principal toes on each foot, the center one considerably larger and the two side toes evidently of little use. The splint of the first toe had disappeared and that of the fifth was now vestigial.

During the Miocene time, as the great western plains developed from forests to grasslands due to a gradually increasing flow of cool dry air from the north, the horsed forebears converted from timid forest browsers to high speed grass grazers. The "horse" of this time was Merychippus (Z,28), of pony size,' with a longer neck and teeth adapted for grazing grass,__ and two side toes, almost the splints of today's horse.

Pliohippus (Z,28) ruled the next epoch, the Pliocene, up until one million years ago. He was a true miniature horse, donkey-sized, with a completely developed hoof. The development of Equs, the horse of today, took the final million years of geologic time—the Pleistocene, in which we still live. His fossil remains are found all over the American Southwest up to ten thousand years ago. (Z,29)

*Due to the large number of footnotes in the text, we have adopted the anthro-pological method of notation. For example, our first footnote refers to page 24 of the reference listed as "Z" following the text.

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