Half a millennium before Columbus’ calamitous 1492 arrival in the Caribbean, DNA from the Americas may have infiltrated the European genome by way of a woman brought to Iceland by Vikings. That’s the potential import of a widely-reported study that finds traces of a genetic variation seen among American Indian populations in four Icelandic lineages who likely share a common ancestor brought from North America before 1700. The variation, which occurs in mitochondrial DNA passed down only through the mother’s line, is one of several markers that was present with the founding populations of native North Americans arriving 14,000 years ago. The Icelandic version has drifted in ways that suggest it originated in an American Indian woman who lived around 1000 AD.