The land bridge theory suggests that a land bridge once existed between Asia and North America, allowing humans and animals to migrate from one continent to the other. The theory has been widely accepted by archaeologists and scientists, although there are alternative theories that suggest different routes for the first Americans. The Bering Land Bridge is the most well-known and accepted theory, and it suggests that people crossed over Beringia, the land bridge that is now submerged, from Asia to America. The theory is supported by archaeological and genealogical connections between Asia and Americas indigenous populations.

The Bering Land Bridge emerged far later during the last ice age than previously thought, according to a new study. The study shows that the land bridge appeared only 35,700 years ago, which shortens the window of time that humans could have first migrated from Asia to the Americas across the Bering Land Bridge. The study also indicates that there may be a less direct relationship between climate and global ice volume than scientists had thought, casting into doubt some explanations for the chain of events that causes ice age cycles.