During the first major glaciations of the late Pliocene (2.6 million years ago) and into the Pleistocene, Equus species crossed to the Old World. Some entered Africa and diversified into the modern zebras. Others spread across Asia, the Middle East and North Africa. Others moved across Asia and Europe as true horses. Other Equus species spread into South America to become extinct there. Small feet for mountains, large ones for plains.