The Native Americans are the indigenous peoples of the United States, including Alaska. They migrated to the Americas from Eurasia in prehistoric times, across a land bridge that once connected the two continents across what is now the Bering Straits. They spread across the continent, evolving into several, distinct ethnic groups and tribes, each with their own, very rich, mythology. The mythology of the Native Americans was mainly oral, and was written down and recorded only with the advent of the Europeans in the late 15th century.