[quote] Too much UV penetrating the skin (too pale-skinned under intense sunlight) increases Vitamin D but reduces folate. Lack of folate causes neural tube defects in the fetus, causing such congenital abnormalities as craniorachischisis, anencephalus, and spina bifida, leading to many miscarriages. [/quote]

So the Europeans had adapted to their environment, changed to a grain diet, suddenly had too little vitamin D. This would mean they would increase their vitamin D, but reduces folate, and therefore increase the number of miscarriages?

Seems like a simple way to test if this hypothesis is actually true. Just look at some historic numbers of the number of miscarriages with those diagnoses (these days pregnant women in Europe get folate supplements).