> Independently, there is a strong correlation between having low Vitamin D levels and living in an environment to which dark skin is not adapted to.
Honest question: what skin color is actually adapted to western Europe or much of North America? Virtually everyone I know with a lighter skin tone needs to apply sunscreen for any outdoor activity to avoid rapid sunburns, and virtually everyone I know with a darker skin tone (jokingly or not) suspects they have a Vitamin D deficiency.
There is no one such skin color for the latitude range you are describing.
Just look at the “average” skin color of whatever ethnicity has been in a particular environment for tens of thousands of years. Native Americans clearly have darker skin than Anglosaxons.
Also, much of western Europe has been colonized by peoples that previously spent thousands of years up further north. The weather in Britain is different from France, and so forth.
Honest question: what skin color is actually adapted to western Europe or much of North America? Virtually everyone I know with a lighter skin tone needs to apply sunscreen for any outdoor activity to avoid rapid sunburns, and virtually everyone I know with a darker skin tone (jokingly or not) suspects they have a Vitamin D deficiency.