The equid family evolved in North America. The first species of the genus Equus to reach Eurasia, more than two million years ago, was the zebra-like or stenonine Equus stenonis. Caballine horses appeared later. The fossil record of caballine horses in Eurasia during the Pleistocene is quite good, but horse taxonomy is complicated and still controversial (e.g., Kurtén 1968; Kahlke 1994; Guérin 1996).
