The article states that white europeans "could have" evolved 5500 years ago. Then again, maybe not.
Actually their problem word is 'switched'.
I don't think they're saying that vitamin D effects melanin production. This would be survival of the fittest and the fittest would have been the lighter skinned in a northern agricultural society.
You speak the difference between a theory and the truth.
One is maybe, maybe not and the other is . . .
I think the argument, which wasn’t well stated, goes something like this.
Vitamin D is necessary, without it, you die.
Before agriculture, sufficient Vitamin D was available through the food that was eaten.
When people in Northern Europe started agriculture, there was not enough Vitamin D in the food.
People with lighter skin make Vitamin D easier than people with darker skin.
People with darker skin died sooner than people with lighter skin in Northern Europe from conditions related to Vitamin D deficiency. The people with the lightest skin would live the longest, and reproduce.
Perhaps there was the flu back then.
http://www.freerepublic.com/focus/news/2325254/posts
Vitamin D is recommended for Swine Flu.