What happens if thousands of years ago a significant tribe of early humans made their way above the Arctic Circle and hung out for a few thousand years in virtu

What happens if thousands of years ago a significant tribe of early humans made their way above the Arctic Circle and hung out for a few thousand years in virtual isolation genetically? Until recent history of course, and those genetics are all mixed up everywhere by now? What does natural selection look like in a place where the sun doesn't go down every day anyhow? And nobody there has ever known anything different?