Sediment cores from Alaska and the Bering Sea support genetic evidence that the first human settlers of the New World spent thousands of years inhabiting Beringia, the region that included the land bridge between Siberia and Alaska, scientists say.

The Bering land bridge measured as much as 1,000 miles (1,609 kilometers) from north to south and as much as 3,000 miles (4,828 kilometers) from west to east. Scientists once thought this vast tract consisted mostly of tundra steppe, a treeless environment incapable of supporting a large human population.

But in recent years paleoecologists—scientists who study ancient environments—have been drilling sediment cores in the Bering Sea and in bogs in Alaska. The samples have yielded plant and insect fossils, as well as