Farley Mowat wrote a book titled “Farfarers,” in which he postulated that Vikings were not the first Europeans to colonize Greenland or North America. He proposed that instead inhabitants of northern Britain ventured far to seaward and colonized both places some two to three centuries earlier than the Norse.
His belief is based on rather flimsy (in my opinion) archaeological evidence from rock piles in the Canadian high arctic, that he believes resemble similar ruins in the Shetland and Orkney islands.
If you read the book, you can form your own conclusions.
He is my cousin that is why I was curious. I figured it would center around Scotland and Ireland. Our family land and castle is in John O’Groats and no doubt he has been there.