What then was the environmental factor that made white skin and blonde hair so beneficial? Unless by natural selection you mean sexual selection.
This whole thread talks about how white skin blue eyes isn't superior to more melanized skin and eyes. So why did this gene spread so quickly?
Like
@aaaaaaa mentioned those phenotypes would be more likely to spread underground.
One benefit that wasn't mentioned in the thread was that it is easier to identify and see blemishes, cuts, bites and infections on lighter skin. Especially since having less melanin can cause a lot of skin issues.