Fossil records of the Equine show a line of evolution from a tiny, multi-toed mammal. The earliest horse resembled it's later descendants in few ways - browsing and walking on all fours seem to be the extent of similarity. Of course the actual coloration and coat pattern of these early mammals will always be debated, but some scientist have decided that spotting and striping would be logical choices. In fact, a 13 year study of the fossil "horses" found preserved in the La Brea Tar Pits in Los Angeles suggested that they were instead zebras or Quaggas. The study also went so far to suggest that horses and donkeys were nothing more than zebras in which the stripe pattern had been partially lost.
All equines began 100 million years ago with the EOHIPPUS (also called the Dawn Horse), a small fox-like creature with 4 toes on the forefeet and 3 on the hind. The tiny mammal eventually left its original forest habitat for the open plains, following the spread of grasses. These pre-equines began slowly to adapt to a grazing way of life, increasing in various sizes and numbers during the Miocene era. By the advent of the Pliocene era, herds had begun to journey across the now-extinct land bridge into Eurasia, forming two important branches of the Equus family - the HIPPARION and the PLIOHIPPUS.
The former traveled on the Far East and North Africa where they mysteriously disappeared, the latter flourished and went on to become the first soliped (equus with single-toed, solid hooves).
It should be noted that is believed that one branch of the North American Pliohippus migrated to South America only to become extinct and had to be reintroduced to that region from European stock by man.
By now the world had formed into separate continental land masses with natural barriers (oceans, mountains, deserts) forcing Equus to evolve in different environments and zones:
*- The Zebra in southern and Eastern Africa
* the true Ass in Northern Africa
*The Asiatic Ass or Onagers ranging from Arabia to Europe and Eastward to China
-* The horses north from Spain and France and westward to Mongolia.
Though much of these territories overlap, the new species did not interbreed with one another. Instead, the TYPES bred among themselves and began to diversify. The northern Horses became heavier and thicker skinned, and evolved into the heavy draft types as well as various pony breeds. In comparison, the southern horses became smaller, more compact and agile, resulting in the refined Arabian, Barb, and other light strains.
Being smaller and quieter in temperament, the wild ass eventually allowed himself to be driven away from good fertile pasture by his fiercely competitive horse cousins, and forced into the outer desert regions. Evolution in the desert refined the ass into a hardy, fine-limbed animal, with a portion of the African variety branching off to create offshoots that became the domestic donkey family. As the donkeys moved north, they became stockier, heavy headed, with shorter limbs and shaggy coats. Only the larger ears, small upright hooves, and light-colored "points" remain as evidence of the desert origin. The Asiatic wild ass developed into several subspecies, but remained in its same primitive state, never evolving different types or contributing to the gene pool of the domestic donkey.
Since the advent of true horses, several breeds have become extinct and are known only by fossil records (South American Horse, Giant Horse, American Zebra, La Brea Tar Pit Quagga). In addition, at least six "modern" breeds have now become extinct. These are the Tarpan (Equus Cabbalus gmelini), the Spanish Jennet, the Anatolian Wild Ass and Syrian Onager, the Algerian Wild Ass and the African Plains Quagga (Equus Quagga quagga). Other species are in serious danger of extinction, among them the French Poitou Donkey, the Syrian Wild Ass, the Persian Onager, Nubian Wild Ass, Przewalski (Mongolian Wild Horse), and the true Burchell's Zebra. The North African Wild Ass is believed to be extinct in it's pure form, but some of it's blood is still found in feral donkeys of the Sahara. One particular strain of Burchell's zebra, those with the least striping, died out in the early 1900's.
Some species of Equine are slowly being bred back, either from captive Zoo populations or by "recreative" efforts. The Tarpan and the Cape Quagga are two breeds which are being "reconstructed"; by rebreeding efforts based on genetic research of breeding and breed type.
New "Breeds" are always being created from existing ones, for example the Aralusian (Arabian and Andalusian) or the Azteca (Quarter Horse, Andalusian and Criollo). By selectively crossing individuals with the desired traits, the breeder can create (after many generations) a horse with the exact characteristics and percentage of the parent blood desired.
