Horse, Equus caballus (Linnaeus, 1758), is a herbivorous animal of the genus Makoma. Tamed by humans 4,000 years ago. Przewalski's horse (66 chromosomes) and domestic horses (64 chromosomes) can hybridize with fertile offspring, and horses were a major driver of agricultural production, transportation, and military activities in ancient times. There are about 200 horse breeds in the world. With the development of productivity, the improvement of scientific and technological level, and the invention and wide application of power machinery, horses play a smaller and smaller role in real life. Horses are mainly used for equestrian sports and the production of breast meat, and the amount of rearing is greatly reduced. However, in some developing countries and regions, horses are still mainly used for military service and are an important source of service strength.
Proto-hoofed beast
Archaeopteryx
The ancestors of horses were Hyracotherium Owen =Eohippus Marsh, who lived 50 million years ago in the Cenozoic, Tertiary, and Eocene. Their bodies are only the size of foxes. The skull is small, the teeth are simple in construction, and the crown is low. 4 fore feet land on the ground and 3 toes on the hind feet. The back is curved and the spine is flexible. It lives in the forests of North America and feeds on young leaves. About 10 million years later, it was not until the Oligocene that the Mesohippus Marsh (Middle Horse) appeared. It's as big as a sheep. Both the front and rear feet have 3 toes, and the middle toe is significantly enlarged. The buccal teeth are still low crowned, and the tips of the molar teeth have been ridged. It still lives in the forest and feeds on young leaves. More than 10 million years later, by the Miocene, merychippus Leidy had appeared. Both the front and back feet have 3 toes, but only the middle toes walk on the ground and the lateral toes degenerate. The body was as big as a modern pony. The limbs are longer and the crown of teeth is higher. The dorsal ridge changed from arc to hard straight, from good at jumping to good at running. The molars are intricately ridged and chalky filled, indicating that the feed has shifted from young leaves to hay. The steppe ancient horse has changed from a forest life to a grassland life, the high-toothed crown molars are suitable for grinding hay, and the running limbs can escape the attack of predators.
The evolutionary history of horses
In the early Pliocene, Pliohippus appeared, with a larger body, a higher crown of teeth, a more developed middle toe of the front and back feet, and a complete degeneration of the second and fourth toes. In the Pleistocene, the Equus Linnaeus appeared, with a body the size of a modern horse, a fully developed middle toe, a hard hoof at the end of the toe, a higher tooth crown, and more complex folds on the chewing surface, reflecting a high degree of adaptation to galloping on the steppe and chewing hay. Before the Miocene, equine animals were mainly distributed in north American forests, and migrated to Eurasia only during the Miocene. During the Pliocene and Pleistocene, north American horses also expanded to South America, but the South American species soon became extinct. By the Holocene, North American horses were also on the extinct. Only the descendants of Eurasia prospered and developed.
horse
The Pleistocene Equus samenensis unearthed in northern China and the wild horses (Equus przewalskii) that still exist in Gansu, Xinjiang and Mongolia are representative of equine animals. Modern horses are domesticated and bred by wild horses. Horses had several branches in the Middle and Pliocenes: an-chitherium V. Meyer distributed in North America and Eurasia in the Miocene; Hipparion Christol in North America and Eurasia in the Pliocene; and Hippidium in Pleistocene South America, indicating that horse evolution did not develop in a straight line. Historically, some paleontologists have believed that organisms always evolved in a given direction based on the evolutionary trends of horses (from small to large, number of toes from many to few, and crowns from short to tall). The age of a horse is identified according to the condition of the teeth. [1]
<h3>Resources</h3>
1. The Evolution of horses [Cited 2017-04-16]
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