Pity poor Leif Ericsson. The Viking explorer may well have been the first European to reach the Americas, but it is a certain Genoan sailor who gets all the glory. Thanks to evidence that has until now consisted only of bare archeological remains and a bunch of Icelandic legends, Ericsson has long been treated as a footnote in American history: no holiday, no state capitals named after him, no little ditty to remind you of the date of his voyage. But a group of Icelandic and Spanish scientists studying one mysterious genetic sequence — and one woman who's been dead 1,000 years — may soon change that.

Ten years ago, Agnar Helgason, a scientist at Iceland's deCODE Genetics, began investigating the origin of the Icelandic population. Most of the people he tested carried genetic links to either Scandinavians or people from the British Isles. But a small group of Icelanders — roughly 350 in total — carried a lineage known as C1, usually seen only in Asians and Native Americans. "We figured it was a recent arrival from Asia," says Helgason. "But we discovered a much deeper story than we expected."...