What are some theories on the origins of the Native Americans?

Several theories exist on the origins of the Native Americans, including the Land Bridge Theory, the Atlantic Theory and the Solutrean Hypothesis. However, there is no clear archaeological evidence to completely sustain any of these theories.

The Land Bridge Theory, also referred to as the Bering Strait Theory, was proposed in 1930 and is widely accepted in the scientific community, as of 2015. The theory states that the first people to inhabit the New World migrated across the Bering Land Bridge tracking large animal herds. The Atlantic Theory mentions that humans reached America by boat, coming from Europe. The Solutrean Hypothesis suggests that early European people migrated to North America in prehistoric times.