The prehistory of the Americas (North, South, and Central America, and the Caribbean) begins with people migrating to these areas from Asia during the height of an Ice Age. These groups are generally believed to have been isolated from peoples of the "Old World" until the coming of Europeans in the 10th century from Norway and with the voyages of Christopher Columbus in 1492. The ancestors of today's American Indigenous peoples were the Paleo-Indians; they were hunter-gatherers who migrated into North America. The most popular theory asserts that migrants came to the Americas via Beringia, the land mass now covered by the ocean waters of the Bering Strait. Small lithic stage peoples followed megafauna like bison, mammoth (now extinct), and caribou, thus gaining the modern nickname "big-game hunters." Groups of people may also have traveled into North America on shelf or sheet ice along the northern Pacific coast.