DNA analysis have been made on skeletons from Viking tombs. The Mitochondrial DNA (mtDNA) haplogroups found were the same as those found nowadays in Europe, but with a much higher percentage of the now very rare haplogroups I and X.
Haplogroups I and X are each found in only 1% of the modern European population. Haplogroup I has been found in over 10% of the bodies in tested from Viking cemeteries. Other studies also found mtDNA haplogroup X in Anglo-Saxon skeletons, suggesting a possible Germanic origin.
Mitochondrial DNA regulates the body's energy production, as well as muscle power and endurance, among others.
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The Y-chromosome side is more consistent with the present incidence. Ancient Norse appeared to belong mostly to Y-DNA haplogroups I, R1a and R1b (S21+). There are nevertheless great disparities between the regions of Scandinavia. Denmark, along with Friesland, northern Germany and the Netherlands, have the highest incidence of hg R1b. Over 40% of Swedes belong to hg I1a, and another 10% to I1c. In Norway, the three haplogroups have about the same share, but with stronger R1b concentration in the South-West and R1a in the North.
It appears that Scandinavia already shared this variety of haplogroups 2000 years ago. The only thing that has changed over time is the increased blending between the original ethnic groups that converged in northern Europe.
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Dr David Faux suggested the existence of a genetic connection between Scandinavians and Central Asians (PDF). He argues that the presence of haplogroup Q in Scandinavia might be due to the migration of a Hunnic tribe to Scandinavia during the Great Migrations of the 4th and 5th centuries. The Huns were allied to the Goths, whose homeland was Sweden.
Dr Faux also hypothetizes a Central Asian origin of haplogroup R1a, found nowadays in Scandinavia, Eastern Europe, Central Asia and South Asia. This haplogroup might have been associated with the ancient Scythians, among others.