The Retuertas horse: the 'missing link' in the Iberoamerican horse breeds origin?

摘要

The evolution of the horse can be traced through fossil remains to Eohippus, a small, leaf-browsing mammal of the Eocene. Several species and related genera appeared in North America and the Old World during the Eocene. For unknown reasons the Old World species went extinct, but the American species gave rise, in the Oligocene to the genus Mesohippus. During the Pleistocene the genus Equus apparently spread from North America to Asia and Europe via the Arctic-Asia land bridge. Then, suddenly, no oneis absolutely certain why, between 10,000 and 8,000 years ago, Equus disappeared from North and South America. Various theories have been advanced to explain this extinction including destruction by drought, disease, or as a result of hunting by the recently arrived human populations. The fact is that the horse was gone from the western hemisphere by the time human civilizations were emerging in the eastern hemisphere. The submergence of the Bering land bridge prevented any migration from the Old Worldor Asia, and the horse was not seen again on its native continent until the Spanish explorers brought horses by ship in the sixteenth century.