Re: Vikings? Weeell, actually the pattern of "exodus" is a little more complex.
For example those who had murdered or stole cattle etc were, if caught, often declared "nithing" meaning they were outside the protection of the law and in order to escape enraged relatives and/or cattle fondlers they often fled (during the late tenth century and the early eleventh) to the western coast of France. The grandson of one of these thieves/murderers was known to his contemporaries as William the Bastard (a little matter of, ahem, lack of a wedding between his mum and dad although given what he did next the alternative interpretation holds as well).
He landed one day with his cohort of third/fourth generation thieves, murderers and cattle-rustlers on the southern coast of England in 1066 and the rest, as we say, is history. The Vikings never successfully conquered* either Scotland or England (indeed Harold Godwinson trounced a Danish/Norwegian army at the Battle of Stamford Bridge in the same year only to march south to his fuck-up at Hastings), it was in fact the descendants of a bunch who even the Vikings could not stand who managed that trick.
*They actually settled as farmers and traders in many areas where they had control but they did not ever succeed in national conquest.