I’m Shelley Schlender for How on Earth.  Here’s an extended version of an interview about how Native Americans came to be.  It’s about a CU-Boulder study that appeared in Science Magazine in February 2014, and promptly made headlines around the world.  The study involves top-notch detective work that shows how, almost 30,000 years ago, a major Ice Age trapped Asian explorers on a land bridge between Asia and Alaska for 10 THOUSAND years.  Back then, the “Beringia” (bare-IN-gee-ah) land bridge was 30 miles long and 600 miles wide. Glaciers had buried Northern America, but Beringia was just warm enough, the trapped explorers survived and thrived.  They stayed in that pit stop for so many thousands of years, it gave time for the inevitable mutations that can happen in DNA to be concentrated and become distributed throughout the entire Beringian community, which probably included a few thousand people.  When the glaciers finally receded around 15,000 years ago, that DNA signature was with the small band of “Beringians” who then began settling in the Americas.  Their settlements were successful.  Their numbers grew over time to become the millions of people today who still carry “Beringia” in their DNA. Today, we call that distinct, Beringian DNA proof that someone’s ancestors were “Native Americans.”