Heredity has two articles of archaeogenetical note, a paper that surveys differences in the frequency of Scandinavian Y and mtDNA lineages in the lands where the Norse settled, and a free review of that research which puts it in perspective. There shouldn't be anything in these results which surprises anyone, in some places (the Shetlands) the Scandinavians seem to have come as family units, male and female alleles which are traditionally Scandinavian markers are balanced in proportion. In other areas there is a distinct male skew, for example, in Iceland, which is more in line with the plunder, pillage and despoil stereotype of the Vikings. Humans are clever and adaptively flexible creatures who respond to a given situation in varied manners dependent on the parameters that they discern, so it shouldn't surprise anyone that the pre-Christian Scandinavians could sack monasteries and slaughter priests, or, they could also be rather banal family men. Now, if only everyone would acknowledge that One True Explanations usually tend to be highly qualified or restricted to narrow spans of time or ranges of space in the human sciences.

Addendum: Standard caveat, for entertainment purposes only!