“Within a few generations, darker skinned people die out...”
Modern man has been living in northern Europe more than 5,000 years.
actually, northern Europe was covered with glaciers until 10 thousand BC, so you are probably right, but only by a few thousand years.
The problem is that a lot of the information of the past is being rewritten as those DNA studies and more archeology is being done.
I’ve started reading some books on this, and the ideas have changed a lot since I was in college...