What is the Bering Strait Immigration Theory?

It's actually quite simple. The Bering Strait is very narrow. You can have an intuitive experience by looking at the map ~ The environment of the earth has changed for hundreds of millions of years, and the Bering Strait may freeze in cold times ~ So Asians living in Siberia came to America along the frozen strait at that time and began the course of human beings in America ~ Later, the ice melted and isolated America, and these people evolved into Native Americans in a relatively independent environment ~ Until Columbus discovered the new continent.