Final answer:
The primary theory of how Native Americans arrived in North America is via the Bering Land Bridge, with another significant theory suggesting coastal migration along the Pacific coastline. These theories are supported by genetic, archaeological, and linguistic evidence indicating multiple migration events.
Step-by-step explanation:
Most historians believe that the Native Americans arrived in North America primarily through two migration routes. The oldest and widely accepted theory is the Bering Land Bridge migration model. During the last ice age, sea levels dropped to reveal a land bridge called Beringia that connected Asia and North America. This allowed early humans to migrate from Siberia to Alaska in pursuit of megafauna and later spread to populate North and South America. Another significant theory is the coastal migration model, suggesting that people also arrived by following the Pacific coastline, possibly by boat, down from the Bering Land Bridge to South America. This theory is supported by archaeological evidence of very early settlements along the South American coast that predate those in North America. Together, these two main theories—backed by genetic, archaeological, and linguistic evidence—paint a picture of a complex and elongated history of human migration to the Americas.