A European contribution to Native American ancestry could explain two longstanding puzzles about the people’s origins. One is that many ancient Native American skulls, including that of the well-known Kennewick man, look very different from those of the present day population. Another is that one of the five mitochondrial DNA lineages found in Native Americans, the lineage known as X, also occurs in Europeans. One explanation is that Europeans managed to cross the Atlantic in small boats some 20,000 years ago and joined the Native Americans from Siberia.
Dr. Willerslev thinks it more likely that European bearers of the X lineage had migrated across Siberia with the ancestors of the Mal’ta culture and joined them in their trek across the Beringian land bridge.