The horse has had a significant effect on history, from its earliest start, when it was eaten, through the Middle Ages, where it had a remarkable effect on the Agricultural Revolution. Horses have been used as beasts of burden, companion animals, war creatures, and rapid transportation.
Equidae (the horse family) like that of various other mammals first materialized at the start of the Eocene era about 57 million years ago. Earth was a significantly different environment at that time. The weather was much warmer; the topography was primarily wooded, with meager wide-open grasslands and prairies. Animals were living at the Arctic Circle. Europe and North America were a good deal closer together physically. Because of the extinction of the dinosaurs and other animals 65 million years ago, several biological voids were formed, among them recesses for medium-to-large-sized herbivores.
The ancestors of the modern horse walked only on the tip of the third toe and both side toes. Skeletal remains display wear on the back of both sides of the metacarpal and metatarsal bones, which are the leftovers of the second and the fourth toe. Modern horses keep the splint bones; some consider them useless attachments, however, they do perform an important function in supporting the carpal joints (front knees) and even the tarsal joints (hocks).
Over a great deal of time, the teeth of the horse experienced major changes. The original teeth were short, "bumpy" molars that steadily altered into long (as much as 3.9”), coarsely cubical molars endowed with flat grinding surfaces.
Along with the evolution of the teeth, the lengthening of the front part of the head is obvious; the rearward set eye sockets, as well as the short neck of the ancestors lengthened over time, along with equal protraction of the legs; and lastly, the size of the body grew as well.
The ancestors of the modern horse are:
Eohippus
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