It appears that human beings migrated to what is now the North American continent by foot, crossing from the Siberian area of Asia into the territory that has become known as Alaska on a bridge of land connecting Asia with North America. Genetic analysis of DNA markers found in the populations of individuals living in Siberia shows significant relationships with native Americans, lending support to this theory of migration to the Americas.
Estimates are that the arrival of humans on what is now called North America occurred approximately 12,000 years ago. The land bridge used for the crossing is now under water in the area known today as the Bering Strait, between Russia and Alaska. Water levels would have been lower thousands of years ago due to more extensive glaciers covering much of the Earth's land in the past.