What is the Bering Strait Immigration Theory?

According to foreign media reports, scientists from the University of Michigan recently confirmed that all the ancestors of American Indians came from Siberia.

Scientists reached this conclusion after conducting large-scale genetic research. During the research, experts compared the genes of 29 Indian tribes living in North America, Central America and South America, and two groups of Siberian aborigines.

Analysis shows that some ancient aborigines living in Siberia are the direct ancestors of American Indians now. These ancient inhabitants who originally lived in the Asian continent arrived in the American continent through one or more migrations. Scientists say that 1.4 million years ago, the Bering Strait did not actually exist. Alaska and Chukchi were completely connected at that time.

Since Columbus discovered America in 1492, the origin of local Indians has been a controversial topic. Although the version migrated from Siberia is the most recognized, scientists have been unable to determine the exact time of that migration: 72,000 years ago or14,000 years ago?