The development of blue eyes and light hair/skin is indeed mysterious.
It could enhance survival in a cloudy, cold northern climate but as others have pointed out, the Inuit, northern Native Americans, Mongolians and northern Chinese all have darker skins than Europeans and have been in the north for many thousands of years.
Apparently the epicenter of blondes is the area around southern Denmark/southern Baltic shores.
Why there? Nobody as yet has an answer.
My guess is that when human beings pushed north into the Asian steppes to hunt mammoths, both before and after the last glaciation, (40,000 y/a and 15,000y/a) some people developed *both* the mongonlian epicanthic fold (’slant’ eyes)and light coloring. You can certainly see that in the Slavs.
Then they decided to go different ways, and they had a big meeting, and flipped a mammoth’s tooth for who got the slant eyes and who got the blonde coloring, and one went east and one went west, and there you have it.
And so only the ones in the middle have both.
Now is that clever or what?
Perhaps you were not aware of the blue eyed Mongolians? Genghis Khan's Blue Eyes
That’s a goofy theory. Mine’s better.
Somewhere a mutant blond baby girl was born. When she grew to womanhood, men preferred her over all the brunettes. She had lots of babies. The rest is history.
Why there? Nobody as yet has an answer.
That's where the Mother Ship crashed. Geez, I can hardly believe you didn't know that.