My husband and I have thought about this, with Icelandic and Nordic people in mind. We have come to the decision that in such a difficult terrain and climate, only the most physically and mentally tough and capable were able to survive. Everyone was expected to pull their own weight, men and women alike. If you didn't want to, nobody would like you much and probably wouldn't want to take care of you. So...generations of genetic pruning due to a brutal lifestyle.
For example, ancient skeletons of men and women from Nordic countries have shown worn down joints (bone-on-bone) in both genders and that they often died in their 30s. Modern day Iceland, for example shows that most adults have 2 or 3 jobs, showing that the work ethic is still very strong. And what is there to do when it's dark and cold most of the year? Fuck and workout.