I don't think that this is as much a question about history as it is about geography and climate. The scandinavian countries are about as north as it is human possible to surviev.

Summer is short and cold compared to most places, while winter is long and dark. It was not even possible to grow many common food sources such as wheat until the late 18's century. The further north you go, the bigger the problem becomes. So while Denmark and southern Sweden and Norway are relativly densly populated you get less and less population the further north you go, because it gets harder and harder to sustain a big population.