Long before the arrival of the Europeans in the Western Hemisphere in the late 1400s and early 1500s, Asian peoples are believed to have migrated over Beringia—a land bridge that is thought to have existed over the Bering Strait, the waterway that separates Asia (Russia) from North America (Alaska). Scholars believe that during the late Ice Age (known as the Pleistocene glacial epoch, which ended about 10,000 B.C.), a natural bridge was formed across the strait either by ice or by dropping sea levels that exposed landmasses. Asian peoples, who were hunters, are believed to have migrated over Beringia as they pursued large game, arriving in North America as early as 50,000 B.C. These people, called Paleo-Indians, were the first inhabitants of the Western Hemisphere. After their arrival, they spread out across North and South America. The many American Indian groups that were encountered by the Europeans upon their arrival were descendants of the migratory Paleo-Indians.