News Feature: Is theory about peopling of the Americas a bridge too far?

Twenty thousand years ago, the Earth was hostile territory. Hulking glaciers smothered much of North America. Deserts claimed swathes of every continent, and winters were 40 degrees colder than today in some spots. But far to the north lay a sprawling, unlikely haven that stretched frommodern-day Canada to Siberia. This was Beringia, a refuge of tundra and grasslands dotted with wildflowers, ponds, and scrubby willow trees. Mammoths and bison roamed its plains for thousands of years. And, if a controversial theory is to be believed, people did too. Researchers once envisioned Beringia, an area that included the now-submerged land bridge connecting Alaska to Siberia, as flyover country, a mere corridor to the New World. But growing evidence suggests that bands of hunter-gathers from Asia tarried there for thousands of years. An idea originally devised to explain genetic variation among Native Americans is now reaping support from fields as disparate as linguistics and paleoecology. Recent analyses of massive DNA databases and ancient DNA have only shored up the genetic underpinnings of the theory, known as the Beringian Standstill Hypothesis. And archaeological work offers tantalizing—though disputed— evidence that people were living in Beringia at the hypothesized time. Skeptics remain, and proponents admit that it will be a challenge to find conclusive proof that people lingered in a landscape now drowned by more than 100 meters of seawater. Still, the idea “has legs,” says evolutionary anthropologist Drew Kitchen of the University of Iowa, who worked on the hypothesis after