Tuesday, November 4, 2008

Vitamin D and skin color. Part II

Is white skin an adaptation to the cereal diet that Europeans have been consuming for the past five to seven thousand years?

When early Europeans switched from hunting and gathering to cereal agriculture, the new diet may have provided less vitamin D (i.e., from fatty fish), which the body needs to metabolize calcium and create strong bones. There would thus have been stronger selection for endogenous production of vitamin D in the skin’s tissues. Since such production requires UV-B light and since melanin blocks UV, this selection may have favored a lighter skin color (Sweet, 2002). In addition, cereals seem to increase vitamin D requirements by decreasing calcium absorption and by shortening the half-life of the main blood metabolite of vitamin D (Pettifor, 1994; see Paleodiet).

Undoubtedly, lighter skin allows more UV-B into the skin. As Robins (1991, pp. 60-61) notes, black African skin transmits three to five times less UV than does European skin. But is this a serious constraint on vitamin D production? Apparently not. Blood metabolites of vitamin D show similar increases in Asian, Caucasoid, and Negroid subjects when their skin is either artificially irradiated with UV-B or exposed to natural sunlight from March to October in Birmingham, England (Brazerol et al., 1988; Ellis et al., 1977; Lo et al., 1986; Stamp, 1975; also see discussion in Robins, 1991, pp. 204-205).

The vitamin D hypothesis also implies that European skin turned white almost at the dawn of human history. Cereal agriculture did not reach northern Europe until some 5,000 years ago and, presumably, the whitening of northern European skin would not have been complete until well into the historical period. Is this a realistic assumption, given the depictions of white-skinned Europeans in early Egyptian art?

References

Brazerol, W.F., McPhee, A.J., Mimouni, F., Specker, B.L., & Tsang, R.C. (1988). Serial ultraviolet B exposure and serum 25 hydroxyvitamin D response in young adult American blacks and whites: no racial differences. Journal of the American College of Nutrition, 7, 111-118.

Ellis, G., Woodhead, J.S., & Cooke, W.T. (1977). Serum-25-hydroxyvitamin-D concentrations in adolescent boys. Lancet, 1, 825-828.

Lo, C.W., Paris, P.W., & Holick, M.F. (1986). Indian and Pakistani immigrants have the capacity as Caucasians to produce vitamin D in response to ultraviolet radiation. American Journal of Clinical Nutrition, 44, 683-685.

Pettifor, J.M. (1994). Privational rickets: a modern perspective. Journal of the Royal Society of Medicine, 87, 723-725.

Robins, A.H. (1991). Biological perspectives on human pigmentation. Cambridge Studies in Biological Anthropology, Cambridge: Cambridge University Press.

Stamp, T.C. (1975). Factors in human vitamin D nutrition and in the production and cure of classical rickets. Proceedings of the Nutrition Society, 34, 119-130.

Sweet, F.W. (2002). The paleo-etiology of human skin tone. Backintyme Essays.

15 comments:

Anne said...

There is no nutrient as better of the skin coloration as vitamin D. this wealth nutrients is also full of curative properties for the depigmentation disorder. It works against the real auto-immunity responsible for such lack of pigmenting of the body.
Any how fine thing for the pigmentation.

Tod said...

A clean sweep of the anti-rickets skin lightening theory, what does it have going for it now?

The post does not discuss folate but I came across something that I think might be relevant enough to mention.
Folic Acid is rapidly destroyed by UV light says Jablonski, this reduces reproduction so black skin is adaptive under high UV as its protection of folic acid improves fitness. However the chemistry is wrong

Genetic Evidence for the Convergent Evolution of Light Skin in Europeans and East Asians I'm going to cut down on links in any future comments you will be glad to hear.

Anonymous said...

Too early white skin is inconsistent with egyptian art AND the fact that white Gallic population were already abundant in Gauls, millions supposedly (since Julius Cesar killed one million gauls and enslaved another million) and according to romans like Strabon.

But I thought about sexual selection in earlier european hunters gatherers. I still don't get it completely and I need more specfific explanations to understand.

1) Men tend to bang everything they can, white, brown black yellow, doesn't matter.
But we suppose there is fewer men than in a farmer's society. How is that possible ? If men are really the main providers and if they are few, then food is scarse for everybody, including women. If a man die while hunting, his wife will starve and die too. If she is taken by another man, he has to dump his ex first, because he can only provide to one. So, either the ex-wife or the widow will die. In this situation, how can there be so much more women than men ?

2) A hunter, I have no doubt, will bang everything he can, but I have also no doubt he can only provide to one woman and her offspring. Since neotenic traits are attractive to males, if the hunter has a choice, he'll choose to provide to the fair skined woman.
OK, but despite the neontenic attractiveness, what matter are the kids, not the mom. Being white doesn't bring the meat on the table and the fair skinned kids should be, at least, equal in hunting to their father. In fact my intuition is that this form of sexual selection wouldn't be very efficient if the male kids are not better at hunting than their father. Either they are smarter or stronger in addition to be whiter, but there must be something.
But then a feedback loop returns to point 1). If these new white skinned hunters become too good at hunting, then food is not scarce, males survive better, bang everything they can again and sexual selection for white female disapear.

So, sexual selection dependance on male/female ratio creates a negative feed back loop on that selection.
How then can you end up with a 100%white population ?

I am not an anthropologist, just curious, thanks.
RG

Tod said...

Black Africans don't get rickets in Britain but do "In some parts of Africa,... especially in societies where corn is predominant in the diet. here
This article understands some of the reasons "The typical African diet is rich in grains and... leaves that contain inhibitors of Ca absorbtion such as phylates, oxalate...".

Nutritional Rickets in Nigerian Children

Tod said...

Nutritional Rickets In Nigerian Children

Peter Frost said...

Anne,

I read the webpage you linked to, but it has no mention of vitamin D.

Tod,

You raise an interesting point. If a cereal diet causes rickets in Africa and if skin color regulates vitamin D production, one would expect to see lighter skin in African agriculturalists than in African hunter-gatherers. Yet the reverse seems to be the case.

Anon,

Your question is: What happens to unmarried women in a hunter-gatherer society? Typically, they remain childless and become caregivers for their parents and younger siblings.

This leads to a second question: If the number of male hunters is limited and if this limit determines the total number of people who can be provisioned, any excess unmated women will die of starvation. No other factor can balance the food supply with the number of food consumers.

Actually, there is another factor: the unmated women don't have children. A woman with no children can continue to be supported by her parents. She 'earns her keep' by helping prepare their meals and taking care of younger siblings. In contrast, a woman with children requires another male provider and cannot be supported by her parents.

This is partly why loss of virginity in the absence of marriage is much more stigmatized in societies with high paternal investment. If a woman has children without a male provider, she imposes an intolerable burden on her parents.

Tod said...

Sub Saharan agriculturists tend to suffer from nutritional rickets so there must have been a selective force for increased vitamin D to reduce the incidence of rickets.
However, populations evolved by strong sexual selection for men do not seem to have evolved the expected counterbalancing anti-rickets feature at all in their skins. Skin melaninisation has evolved in Black Africans as if vitamin D was irrelevant, which we know it is not. Might we expect some other feature of sub Saharan agriculturists to counter their diet's rickets inducing effect?
The Metabolism of Vitamin D3 in Response to Testosterone

Tod said...

Bikle DD, Ettinger B, Sidney S, Tekawa IS, Tolan K:
Differences in Calcium Metabolism between Black and White Men and Women.
"Environmental factors such as diet and sunlight exposure do not appear to influence racial differences in the levels of the calciotropic hormones or renal calcium excretion".
Mineral Electrolyte Metab 1999;25:178-184 (DOI: 10.1159/000057442
abstract


Kidney International (2003) 64, 737–742; doi:10.1046/j.1523-1755.2003.00129.x

"African Americans with normal kidney function have higher parathyroid hormone (PTH) serum levels and larger parathyroid glands than Caucasians1,2,3,4,5,6,7. They also have higher bone mineral density7,8 and lower serum osteocalcin levels1,2,6, findings that are suggestive of lower bone turnover".
here

Vitamin D and African Americans
"Despite their low 25(OH)D levels, blacks have lower rates of osteoporotic fractures. This may result in part from bone-protective adaptations that include an intestinal resistance to the actions of 1,25(OH)2D and a skeletal resistance to the actions of parathyroid hormone (PTH)".
here

Tod said...

Testosterone inhibits osteoclast formation stimulated by parathyriod through androgen receptor

Testosterone increases osteoprotegerin mRNA expression in mouse osteoblast cells

An update on the honesty of melanin-based color signals in birds
" the role of (i) metals, (ii) amino acids, and (iii) testosterone and social interactions in shaping the extent and intensity of melanin-colored plumage patches. ...Birds whose plumage was experimentally darkened were found to have higher T levels (Safran et al., 2008). This result revolutionizes our perspectives on the physiological costs of animal signals, which now must be evolutionarily viewed and mathematically modeled as important both before and after trait production".

Anonymous said...

First of all, people of African descent deeply resent the term "negroid" to describe black or dark-skinned melanin dominant people. It was termed coined by white slave traders and their descendants, and used in racially offensive manner for many years, and especially during the era of so called "scientific racism", when there were attempts to prove "negros" were different biologically than their black African counterparts, and that they were some kind of new sub-class of humans. So the term became very offensive. It still is. Also, to suggest that "Europeans turned pale at the dawn of human history" is equally offensive. In that it ignores hundreds of thousands of years of the most advanced civilizations on earth, evidenced by the ruins and records they left behind. And implies that "human history" only begin with the advent of the pale-skinned European, who was really an AFrican who settled in Europe and mutated. The pale Egyptian you saw in paintings were in later dynasties within this five to seven thousand year period, when Egypt was in decline and was being invaded by tribes from the north. There were also back migrations occuring after the last ice age. Black people then, as now, were not always "dark" dark-skinned. We varied in colors and shades just like today. Please be attentive of things like this when discussing this important subject.

n/a said...

An update on the honesty of melanin-based color signals in birds

Really amazing lack of critical thought on display here, even by todroy's usual standards.

Tip #1: Humans aren't birds.

Tip #2: "this relationship did not hold in species where the
male plumage is not androgen-dependent (i.e. in gamebirds
and ducks)."

Anonymous said...

I think a lot of oddities can be explained by hybridization between Homo Sapiens and other human species. I know that the theory of sapiens-neanderthal relationships has become unpopular, but it would really solve the skin color puzzle.

Quote from The Neanderthal Theory of Autism: "Recent genetic research have demonstrated that the Out-of-Africa (OoA) model with no interbreeding fails to explain nuclear DNA diversity in Eurasia. Several models of interbreeding that do explain this diversity exists today. It therefore is quite likely that Neanderthals contributed to the Caucasian genome."

Anonymous said...

Quote from The Neanderthal Theory of Autism: "Recent genetic research have demonstrated that the Out-of-Africa (OoA) model with no interbreeding fails to explain nuclear DNA diversity in Eurasia. Several models of interbreeding that do explain this diversity exists today. It therefore is quite likely that Neanderthals contributed to the Caucasian...

What is sad is that the roots of color prejudice, not "racism" since racism is a recent phenonemon that had as its springboard, the TransAtlantic Slave Trade. When European planters needed to find a common divider between the serf classes who were rising up in revolt and themselves. The common divider was phenotypical differences. White people were always an anomaly and were aware they were different than the majority people of color on the planet. That difference became a cause the elites could get the poorer of their pale-skinned kinspeople to rally around. It worked. Launching one of the greatest hoaxes in history. The reality is, it is indisputable that black Africans are the oldest people on the planet and the first and seminal race. That they migrated into Europe, and all parts of the known habitable world. And left their genetic signature in every race that succeeded them. Which is why we all share a common ancestral mother and father. But the roots of prejudice are so deep, some brainwashed whites would rather be related to apes, aliens or neanderthal subhumans than black people. What a sad statement. And what a distance we must go before we are truly civilized and worthy of the higher knowledge our ancestors once possessed.

Neonomide said...

I didn't find anyone mention Vitamin D deficiency and respiratory infections. They are practically married.

Wayse, et al compared 80 children with lower respiratory infections to healthy controls and found children with the lowest 25(OH)D levels were ELEVEN times more likely to become infected. Furthermore, 60,000 IU of vitamin D a week administered for six weeks to 27 children suffering from frequent respiratory infections resulted in a COMPLETE disappearance of such infections for the following 6 months.

http://www.ncbi.nlm.nih.gov/pubmed/15042122

http://www.ncbi.nlm.nih.gov/pubmed/8182788


Apparently it must be a big deal. Perhaps Vitamin D rich diet is the reason why they are less dark skinned than the other people living up north?

The effect on infant mortality must have been enormous. Lighter skinned children would have had better chances to survive, surely.

Eurasia obviously has a lot of latitudal space for flora and fauna to spread - for diseases too.

Influenza and Vitamin D article (Cannell et al. 2008) also brings nice perspective to Vitamin D connection and proves it with a citation to 90+% successful trial using 50 µg/d Vitamin D on Afro-American women:

http://www.virologyj.com/content/5/1/29


The older Cannell et al. (2006) article on the same subject here:

http://www.vitamindcouncil.org/PDFs/cannell-et-al-epidemic-influenza-and-vitamin-d.pdf


Even more Cannell (2008) with cod liver oil and respiratory infections:

http://www.vitamindcouncil.org/PDFs/cannell-et-al-vitamin-d-deficiency-epidemic.pdf


How come I haven't been able to find this theory anywhere before? I'm stunned, really.

Neonomide said...

I said...

"Perhaps Vitamin D rich diet is the reason why they are less dark skinned than the other people living up north?"


I was referring to Inuits.