A two-way strait?

• Position: MIGRATION - Brief article

It's common to think of the land bridge that existed from time to time across the Bering Strait--the 58-mile-wide sea passage that separates Alaska from Russia--as a one-way affair. The route through this area is thought to be how many humans and animals came from Asia into North America. But there were no "Eastbound Only" signs. Scientists have recently determined that the woolly mammoth, a shaggy-haired member of the elephant family, apparently traveled in both directions. Using DNA analysis of mammoth remains, scientists have identified several groups of mammoths. Some were native to Siberia; others had roots in North America. But at some point, say...