The ancestors of today's Native Americans were hunter-gatherers who migrated into North America. The most popular theory says that migrants came to the Americas via the Bering Land Bridge, Beringia, the land mass covered by the cold ocean waters in the Bering Strait. Small Paleo-Indian groups probably followed the mammoth and other prey animals. It is possible that groups of people may also have traveled into North America on shelf or sheet ice along the northern Pacific coast.