- genetic diversity, as well as genetic similarity to the Siberian groups, decreases the farther a native population is from the Bering Strait--adding to existing archaeological and genetic evidence that the ancestors of native North and South Americans came by the northwest route.
- a unique genetic variant is widespread in Native Americans across both American continents--suggesting that the first humans in the Americas came in a single migration or multiple waves from a single source, not in waves of migrations from different sources. The variant, which is not part of a gene and has no biological function, has not been found in genetic studies of people elsewhere in the world except eastern Siberia.
How they ventured south once traversing an icy northwestern passage, however, is another question.
In Rosenberg and his colleagues' study, detailed in a recent edition of the journal PLoS Genetics, the scientists support the idea that humans migrated south along the coasts by boat rather than toughing it out on land.
"A migration route along the coast provides a slightly better fit with the pattern we see in genetic diversity," Rosenberg said.