A big hole in this theory: blacks in North America have no problem producing babies no matter where they live, and they aren't eating many fish livers. The evolutionary pressure of vitamin D deficiency is insufficient to explain how suddenly white skin, not just light skin, appeared. My hypothesis is that white skin, blond hair, blue eyes are mostly cosmetic traits, and they are not mostly from sexual selection but from mothers cultivating them in their children. The temporary blond/blue in most European babies is strong evidence for this. The blond hair doesn't disappear until about age 5, when a child is no longer so dependent on mom. Do you have an alternate explanation for this phenomenon? What purpose does it serve other than cosmetic?
Milk and other foods get vitamin D added these days.
African Americans still tend to suffer a number of health problems due to vitamin D deficiencies
Blacks in north America have nothing to do with the ancient argument. Currently we all get Vitamin D added to our milk, because rickets used to be such a problem for everyone. Also, although some black Americans are lactose intolerant, it also can be gotten from sardines, and related sources, as well as liver and onions, and cod liver oil which some parents conscienciously give to their children. I did know one child who at age 4 had a severely swollen forehead from rickets (she had a white mother and black father). Vitamin D deficiency causes more subtle signs such as a narrowing of the face and upper jaw arch with crowding of teeth. My mother and I both suffered from this. I then read about this problem in Adelle Davis’ book “Let’s Have Healthy Children”. My first son’s face was round as an infant, but started to narrow as he reached one year. I then added cod liver oil to his diet and his face subsequently rounded out again. Although he had to have his wisdom teeth pulled, he did not need the thousands of dollars for orthodontic work that I did. Also, as I restricted sweets in his diet to only 4 times a year (Easter, Halloween, Christmas, and his birthday) he at age 40 has never had a single cavity.
The genetics of skin color is quite fascinating. There are actually 4 genes for skin color in each parent. Thus if a WWWW mates with a BBBB, the child will be WWBB. However, if two WWBB’s mate you can have everything from all W or all B to BBBW, BBWW, or BWWW. Regarding the light coloring of children which I have noticed myself, it makes sense that this would have a survival advantage if babies are being kept protected in tents or caves, covered up against the cold, and in general having less exposure to the sun than when they are older and running around on their own.