The Beringian theory is based on people migrating from Siberia across the land bridge that was revealed in the Bering Strait area because the sea level decreased during the last Ice Age. The Laurentide ice sheet receded to expose gaps in which the early humans voyaged through and spread southward. Small groups of hunters followed game animals across the land bridge and set up settlements in America. In Clovis, New Mexico the first ever clovis evidence was found by archaeologist Johnson. The artifacts were dated to 12,000 years ago.

The Maritime theory is based on early humans in watercraft moving South along the Pacific coast From modern-day Russia past Alaska, Canada, and Central America to Monte Verde, Chile by 12,500 years ago or earlier.