Dogwood, I realise that a caucausian person would perish ultimately in the sub artic, but we have a tribe of Eurasians called the Evenk(e) in Northern Europe and Russia who have survived in the sub artic Tundra for millenia. They are reindeer herders for the majority of their subsistence and they are still there. They usually die from the terminal desease called life and not starvation. They are also generally muscular and not greatly overweight.
How do they fit into your theory?