Friday, July 2, 2010

The vitamin-D hypothesis and ancestral Europeans


Above - Artist's reconstruction of pre-Viking Age boat
Below – Prehistoric rock paintings of boats (Scandinavia)
Some writers argue that European skin became white to offset a decline in dietary vitamin D. Pre-agricultural diets, however, were rich in vitamin D only among coastal Europeans who consumed fatty fish.

The ‘vitamin D hypothesis’ is often invoked to explain differences in skin color among human populations (Loomis 1967; Murray 1934). As modern humans spread out of Africa, they entered northern regions, like Europe, where sunlight is weaker and less conducive to synthesis of vitamin D by the skin. Thus, to maintain the same level of vitamin-D synthesis, there was strong natural selection to depigment the skin and let the sun’s rays penetrate it more easily.

This might explain the whiteness of Europeans, but what about the darker skin of northern Asians and native North Americans? They too live at high latitudes. And they too receive much less sunlight than do tropical peoples.

The standard reply is that they get enough vitamin D from their diet, specifically fatty fish, so natural selection has not lightened their skin to the same degree:

The Eskimo though deeply pigmented and living in a dark habitat, nevertheless is notoriously free from rickets. This is due to his subsisting almost exclusively on a fish oil and meat diet. […] Because of his diet of antirachitic fats, it has been unnecessary for the Eskimo to evolve a white skin in the sunless frigid zone. He has not needed to have his skin bleached by countless centuries of evolution to admit more antirachitic sunlight. He probably has the same pigmented skin with which he arrived in the far north ages ago (Murray 1934).

Actually, this explanation holds true only for a minority of northern natives, i.e., the Inuit, the Aleuts, and some other coastal peoples. Fatty fish is absent from the diet of non-coastal peoples, i.e., most Algonkians, Athapaskans, and indigenous Siberians. Yet the latter are if anything darker-skinned than the Inuit.

Conversely, fatty fish has long been a staple of Scandinavians, who nonetheless are very white-skinned. And the word ‘long’ is no exaggeration: skeletal remains of Danes living 7,000-6,000 years ago have the same carbon isotope profile as those of Greenland Inuit, whose diet is 70-95% of marine origin (Tauber 1981).

But the vitamin-D hypothesis has another shortcoming: Europeans did not turn white until long after their ancestors came to Europe some 35,000 years ago. If we examine the various alleles that lighten European skin color, the time of origin seems to be relatively late. At the SLC45A2 (AIM1) gene, the date is ~ 11,000 BP (Soejima et al. 2005). At SLC24A5, the date falls between ~ 12,000 and 3,000 BP (Norton & Hammer 2007). As a Science journalist commented: “the implication is that our European ancestors were brown-skinned for tens of thousands of years” (Gibbons, 2007).

This has led to an updated version of the vitamin-D hypothesis. It has two postulates:

1. Selection for white skin began long after modern humans entered Europe.

2. The cause was not the weak sunlight of Europe’s high latitudes, but rather less intake of vitamin D from food sources. This happened when a diet of terrestrial game, fish, and wild plants gave way to one based on grains and livestock—in short, the advent of agriculture (Khan & Khan 2010; Sweet 2002).

If we pursue this line of reasoning, Europeans must have turned white almost at the dawn of history. We know that agriculture spread into southeastern Europe from the Middle East around 9,000 years ago. By 7500 BP it had reached a line stretching from the Netherlands through Central Europe and to the Black Sea. Thus, the extreme skin depigmentation of northern Europeans would have occurred over the last seven millennia or so. Actually, the time frame is even narrower, since white-skinned Europeans appear in ancient Egyptian art from the second millennium B.C.

So we’re left with around 3,000 years, at most. Is this pace of phenotypic change consistent with selection due to weak sunlight? Not according to current opinion. Brace et al. (1999) studied how skin color varies among Amerindians, who have inhabited North and South America for 12,000-15,000 years, and among Aborigines, who have inhabited Australia for some 50,000 years. If latitudinal variation in skin color tracks natural selection due to the intensity of sunlight, calculations show that this kind of selection would have taken over 100,000 years to create the skin-color difference between black Africans and northern Chinese and ~ 200,000 years to create the one between black Africans and northern Europeans.

But there’s another problem. How do we know that ancestral Europeans did ingest much less vitamin D when agriculture replaced hunting/fishing/gathering? This question is met only with affirmations, e.g. “Because of the lack of meat and fish in the diet of the new farmers, vitamin D intake would have been drastically reduced” (Khan & Khan 2010). No one seems to have actually quantified vitamin-D intake before and after the advent of agriculture.

To gain a rough idea, we can consult Loomis (1967) for a listing of vitamin-D content by food source:

Food source - Vitamin D content (I.U./gram)

Halibut liver oil – 2,000-4,000
Cod liver oil – 60-300
Milk – 0.1
Butter – 0.0-4.0
Cream – 0.5
Egg yolk – 1.5-5.0
Calf liver – 0.0
Olive oil – 0.0

Sweet (2002) provides a longer list:

Food source – Vitamin D content (I.U.)

Cod liver oil, 1 tbs – 1,360
Salmon, 3.5 oz. – 360
Mackerel, 3.5 oz. – 345
Herring, 3.5 oz. – 315
Sardines, 3.5 oz. – 270
Eel, 3.5 oz. – 200
Shrimp, 3.5 oz. – 150
Beef liver, 3.5 oz. – 30
Egg, 1 whole – 25
Beef, pork, chicken, 3.5 oz. – 20
Cheese, 1 oz. – 4
Unfortified milk – 0
Unfortified cereal - 0

Clearly, fatty fish has a lot of vitamin D. But the same cannot be said for terrestrial animals, like calves. Furthermore, the figures from the first list were initially published in 1938, when most cattle were kept outdoors and exposed to sunlight. These were also American cattle. They lived farther south than the game animals that ancestral Europeans once hunted and whose flesh probably had a lower vitamin-D content.

Thus, before agriculture, Europeans got substantial vitamin D from their diet only in coastal regions, like Scandinavia, where people ate fatty fish. Europeans who lived inland—the majority—did not have this dietary source. One might counter that the issue is not vitamin-D content per se but rather substances, like phytic acids in cereals, that deplete the body’s supply of calcium and phosphorus. The advent of agriculture would have artificially increased the body's need for vitamin D.

Perhaps. Ultimately, this debate will end only when we know the precise time frame when Europeans became white. We already know that this time frame considerably postdates the arrival of modern humans in Europe (c. 35,000 BP). If it significantly predates the arrival of agriculture (after 9,000 BP), the vitamin-D hypothesis will be out of the running, even in its updated form.

This puzzle will then be placed within a larger one. Why do Europeans possess such unusual color traits that involve not only the skin but also the hair and the eyes? How did they evolve so rapidly a white skin and a diverse palette of eye and hair colors? If humans were any other animal, such traits would be readily put down to sexual selection.

References

Brace, C.L., Henneberg, M., and Relethford, J.H. (1999). Skin color as an index of timing in human evolution. American Journal of Physical Anthropology, 108 (supp. 28), 95-96.

Gibbons, A. (2007). American Association Of Physical Anthropologists Meeting: European Skin Turned Pale Only Recently, Gene Suggests. Science 20 April 2007, 316. no. 5823, p. 364 DOI: 10.1126/science.316.5823.364a http://www.sciencemag.org/cgi/content/summary/316/5823/364a

Khan, R. and B.S.R. Khan. (2010). Diet, disease and pigment variation in humans, Medical Hypotheses, early view.

Loomis,W.F. (1967). Skin-pigment regulation of vitamin-D biosynthesis in Man, Science, 157, 501-506.

Murray, F.G. (1934). Pigmentation, sunlight, and nutritional disease. American Anthropologist, 36, 438-445.

Norton, H.L. & Hammer, M.F. (2007). Sequence variation in the pigmentation candidate gene SLC24A5 and evidence for independent evolution of light skin in European and East Asian populations. Program of the 77th Annual Meeting of the American Association of Physical Anthropologists, p. 179.

Soejima, M., Tachida, H., Ishida, T., Sano, A., & Koda, Y. (2005). Evidence for recent positive selection at the human AIM1 locus in a European population. Molecular Biology and Evolution, 23, 179-188.

Sweet, F.W. (2002). The paleo-etiology of human skin tone.
http://backintyme.com/essays/?p=4 (visited on July 10, 2008).

Tauber, H. (1981). 13C evidence for dietary habits of prehistoric man in Denmark. Nature, 292, 332-333.

45 comments:

Tod said...

A Decreasing Gradient of 374F Allele Frequencies in the Skin Pigmentation Gene SLC45A2, from the North of West Europe to North Africa

"The highest allele frequency is observed in Denmark"


Denmark has the lowest digit ratio in the world and is also where "one in 8 children is born to couples where medical assistance is needed due to low male sperm count".


The latest from Nina G. Jablonski and George Chaplin
Human skin pigmentation as an adaptation to UV radiation

I don't think the authors are taking the following studies on board Serum folate levels after UVA exposure: a two-group parallel randomised controlled trial

5-Methyltetrahydrofolate inhibits photosensitization reactions and strand breaks in DNA

White skinned women have been intensively sunbathing for decades, pregnancy problems or Folic acid deficiency among sunbathers would be noticed. Sunbed users should have a very high rate of birth defects - do they?

A study from South Africa shows higher birth defects in whites but Neural tube defects are caused by multiple genes and environmental factors.

ItsTheWooo said...

There is a fundamental problem with your reasoning (that caucasians are diversely colored, in the way birds like peacocks are diversely colored - for sexual attraction purposes).

The problem is that caucasians really are *not* that diversely colored.

There are no additional pigments in european people not found in other people. All europeans are noted by is that this group of humans has a lack of pigment. For example, incomplete pigment in the eyes results in the appearance of green, and total lack of pigment in the eyes results in the appearance of blue. Dark green would be a slight lack of pigment, light green would be a slight presence of pigment.
It appears as if there are all these diverse colors but in reality you just have varying intensities of expression for genes coding for pigment in the eyes.
There is no "green" pigment and no "blue" pigment, just pigment.

Once you understand that the issue is partially expressed genes affecting the amount of melanin pigment, as opposed to new genes which make new colors, it becomes obvious the cause of such "diversity" in europeans is probably the circulation of novel recessive genes, for no reason other than the fact that europeans are highly inbred.

It's like, I have a bunch of cats that have been inbreeding for decades in my neighborhood. These cats have acquired many interesting and unique features. The cats have extra toes, although some have normal toes. Some cats have a very short almost absent tail, others have a short tail, and others have a normal tail. Their colors are either white and black, white black and brown, or white and brown.

The reason these cats have such a diverse array of features is because the recessive traits for their coloring and their toes and their tails have been circulating for generations due to the close inbreeding going on in my neighborhood among these cats.

In other words... It's a few novel genes being circulated and expressed at different intensities.

I don't think the cats were like "oh, you have a short tail, lets get busy because I like short tails". It's more like "You're the only cat around and it's spring so lets get busy".

I tend to think it was sorta like that in europe. Recessive genes for decreased pigmentation were given an opportunity to circulate resulting in slightly pigmented eyes (green) or absent pigmented eyes (blue). ... slightly pigmented hair (light brown, gold) or nearly absent pigmented hair (very pale blonde).


I tend to think that white skin did not evolve, was not selected for, but merely represents relaxed selection pressure for darker skin due to lack of UV exposure.

Dark skin is important when you live near the equator, you can sorta get massive burns and die if you don't tan or don't sport a year round tan. Burns can be fatal, or at least reduce fitness if your skin is burned and compromised.

As people leave the equator, get less UV exposure, such selection pressure is relaxed and there is an opportunity for pale skin to emerge.

In general, the paleness of an animal correlates with lack of light... I see no reason why humans would be different. Any cave dwelling animal is invariably pale, pigmentless. Early humans, europeans, were "cave men" and did not have to deal with light the way people in africa do.

The varying color combinations of europeans are all just different strengths of the same old pigment. No new colors, just absent, short, or long tails.

ItsTheWooo said...

And I would add that northern asians are quite often pale.

When I visualize a person from japan I imagine them to have very pale (sparsely pigmented) yellow pigmented skin, dark black (densely pigmented) straight hair and dark brown/black eyes (densely pigmented).

Pigment trends of skin generaly do seem to follow patterns of UV exposure.

http://www.webexhibits.org/causesofcolor/images/content/melanin/Map_of_skin_hue_equi3Z.jpg

Some of these trends may be put to migration patterns too (such as that chunk of white in south africa)... but generally you see paleness away from the equator and darkness toward it. Recent migration affects things slightly.

And this map also reflects the fact that northern asians are actually relatively pale.

I don't think vitamin d has anything at all to do with anything.

Tod said...

Barrier requirements as the evolutionary driver of epidermal pigmentation in humans

"Pigmented skin is endowed with enhanced permeability barrier function, stratum corneum integrity/cohesion, and a reduced susceptibility to infections. The enhanced function of pigmented skin can be attributed to the lower pH of the outer epidermis, likely due to the persistence of (more-acidic) melanosomes into the outer epidermis, as well as the conservation of genes associated with eumelanin synthesis and melanosome acidification (e.g., TYR, OCA2 [p protein], SLC24A5, SLC45A2, MATP) in pigmented populations"

Anonymous said...

Tod, give a proper explanation as to what you're trying to argue. Barely any of what you're saying makes sense.

Anonymous said...

On another note Frost, how do you think neanderthals fit in with this? They had light skin yet were polygamous.

Tod said...

Cancer Incidence and Mortality After Treatment With Folic Acid and Vitamin B12

"Treatment with folic acid plus vitamin B12 was associated with increased cancer outcomes and all-cause mortality in patients with ischemic heart disease in Norway, where there is no folic acid fortification of foods."

Anonymous said...

Again, what are you arguing?

Peter Frost said...

Tod,

The low sperm count of Danish men is a result of a relatively recent decline. In a previous post, I argued that this decline, like the increase in testicular cancer, was probably caused by the rising level of urinary estrogen in the environment (due to the generalization of primary wastewater treatment).

http://evoandproud.blogspot.com/2009/03/urinary-estrogen-theory-part-ii.html

Its the Woo,

Natural selection acts on phenotypes, not on underlying mechanisms.

Yes, the different shades of hair and eye colour involve pigments that exist in all humans, and even many non-humans. I concede your point, but it's totally irrelevant.

"the cause of such "diversity" in europeans is probably the circulation of novel recessive genes, for no reason other than the fact that europeans are highly inbred."

Some of these European-specific alleles are recessive and others are not. In any case, even the recessive ones are absent in other human populations. It's not as if they have always been around and are now apparent because of inbreeding. They are specific to Europeans. They arose after modern humans settled in Europe, not before.

Also, Europeans are not more 'inbred' than most populations. I think you mean that Europeans are less genetically diverse, probably as a result of founder effects and bottlenecks.

But aren't you arguing against yourself here? If Europeans exhibit less overall genetic diversity, they should also show less diversity at genes for hair and eye colour. Yet this is the very opposite of what we see.

If white skin were a result of relaxation of selection (as opposed to positive selection), it would not have arisen so fast. The data indicate a rapid "sweep" through the European gene pool. Some kind of selection was at work.

The map you reference was created by Renator Biasutti in the 1940s largely on the basis of guesswork and a few studies using the van Luschan scale. Much of that map is no longer accepted.

If we look at spectrophotometric studies, the difference in skin colour between English and Japanese, for instance, is about a third or a quarter of the difference between English and sub-Saharan Africans.

Anon,

At present, we know nothing about the skin color of Neanderthals. Their MC1R gene had an allele that would produce reddish hair and lighter skin in humans. But no one is sure how this allele would have behaved in a Neanderthal body. There are also other genes involved in skin color, and we still know nothing about their Neanderthal counterparts.

Tod said...

Yes sperm counts have fallen and 2D:4D has increased recently ( and right handedness - more common in women - reached an all time low in Britain round about 1900 according to Chis McManus) but Denmark is still an anomaly in having such startlingly low sperm counts and high 2D:4D compared to other countries which have much the same environmental influences. Urinary estrogen is filtered out nowadays and young Danish men are still the least testosteronized in the world. To put it all down to urinary or other xenoerestrogen in the environment one would need to say why Denmark is still much more badly affected, (eg it is a low lying country so it's something to do with drainage, they have an unusual diet). Considering geography and the Doggerland connection I think Denmark's odd lack of testosteronization compared to other similar westernized north European countries is at least partially due to the Danish population's genetic characteristics. The Danes do have that high frequency of pigmentation genes.




The vitamin D content of meat may be beside the point.
Meat consumption reduces the risk of nutritional rickets and osteomalacia.

"The mechanism by which meat reduces rachitic and osteomalacic risk is uncertain and appears independent of revised estimates of meat vitamin D content. The meat content of the omnivore Western diet may explain its high degree of protection against nutritional rickets and osteomalacia from infancy to old age in the presence of endogenous vitamin D deficiency"

Anonymous said...

Tod, please explain to me what you're arguing for.

Anonymous said...

"Urinary estrogen is filtered out nowadays and young Danish men are still the least testosteronized in the world."

Even moreso than east asians, with their high diets in estrogen-rich foods?

I imagine that's the prime reason for their typically low testosterone levels.

Anonymous said...

My post about neanderthals possibly having light skin was spurred on from remembering Tod's insistence that they must have bee as dark as orangutans due to their polygamy, along with his vehement assertions on neanderthals looking like bipedal gorrilas, based on Vendramini's pop science reconstructions.

Stephen said...

@ ItstheWoo it does not matter what the total number of pigments involved are, the diferent shades are percieved by potential mates as diferent colours and it is quite a diversity of genes that produce these diferent colours so your point is moot. There are plenty of populations much more inbred than europeans, for example aboriginal Australian 50,000 years all by themselves and the Tasmanians an even smaller pocket for the last 10. But all this did was preserve an archaic form of Homo Sapiens as there was less suply of mutations for selection.

Anonymous said...

"But all this did was preserve an archaic form of Homo Sapiens as there was less suply of mutations for selection."

Aborigines aren't "an archaic form of homo sapiens".

Anonymous said...

www.femininebeauty.info/hanihara.flatness.pdf

"The late Pleistocene anatomically modern samples show generally flat faces, comparable to present eastern Asian samples in at least fronto-orbital flatness... As described above, the proportion of frontal and facial flatness in the late Pleistocene among anatomically modern humans roughly combines a deep infraglabellar notch, sagittally flat frontal bones, and marked prognathism with more or less flat faces. Taking this into consideration, it may be possible to interpret the frontal and facial form of Australians as presenting both generalized and specialized features. In a cladistic sense, the distinctive anatomical combination seen in Australian cranial series does not retain a plesiomorphic state. Stated another way (Lahr and Wright, 1996), Australian faces do not reflect the retention of ancestral traits. "

Anonymous said...

Which means what exactly?

ItsTheWooo said...

My point really isn't moot because "brightly colored animals" exhibit multiple PIGMENTS in the SAME animal. A peacock tail has many colors.

A blonde with blue eyes does not, in herself, have a lot of colors to offer.

Humans, single human beings, are not brightly colored. You can have a vodka add with a blonde with green eyes, a red head with blue eyes, and a dark haired woman with dark brown eyes, but each individual woman only has a small number of colors.

I suppose to a heterosexual male, biologically driven to mate with as many healthy females as possible, with access to the media (thus the ubiquitous vodka adds with women of all different ethnicities and backgrounds and colors presented to him)... he could come to the conclusion that maybe color diveristy exists because men think it is sexy.

But, it sorta neglects the fact that women are only colorful when a bunch of them get together and stand next to each other. Individual females are not colorful the way an individual peacock is colorful.

This is actually relevant.

If humans evolved to have stripes of pink on their faces and orange on their wrists and purple on their legs with hair that was the color of the rainbow then maybe that was sexual selection. Maybe humans use makeup for that purpose - women have brightly colored nails on their fingers and toes and cheeks and eyes and lips.

But without makeup, women are quite plain in terms of color (again, speaking only of an individual woman)... attractive or unattractive, perhaps, but not brightly colored. No individual woman is born brightly colored.

But what I see are a tendency for varying types of paleness... with slightly depigmented humans being olive skinned with light brown-dark blonde hair and green eyes, and totally depigmented humans with blonde hair and blue eyes.

Even assuming this basic palate (varying intensities of the same pigment) you don't see that many wacky combinations in europeans. Wacky color combinations (blue eyes and tanned skin; gold hair that is curly with pale skin) is usually only found when light people are interbred with darker people.


I suspect that there may be some role of sexual selection, men preferring diversity in women, but seeing as sooo much research relates color of the eyes and skin to the sunlight (some of that was actually posted above), seeing as my skin color can change with the seasons and is 100% controlled by the amount of UV my skin is exposed to, it is only logical to conclude the primary function of pigment in humans is as an adaptation to UV exposure from the sun.

Anonymous said...

My wild guess is that the lack of sun intensity allowed lighter colors to be selected for - colors that humans may simply naturally prefer. In the Arctic, light exposure can be intense due to the reflection of snow. Europe only gets occasional snowfall, and the continent is very very cloudy that part of the year.

Peter Frost said...

Tod,

Urinary estrogens were eliminated from wastewater in the 1970s (with the spread of secondary treatment). Today, unaffected males would be less than 35 or so. That's close to the average age of childbearing in Denmark, so I think it will be a few more years before any improvement becomes noticeable.

I suspect Danish men are worse off than English men because the sources of drinking water (rivers, lakes) are colder and less conducive to the breakdown of urinary estrogen.

Your reference to meat and rickets is most interesting. Again, the only way to settle this debate is by finding out exactly when European skin turned white.

Its the Woo,

When modern humans spread out of Africa some 50,000 years ago, they had only one allele at the MC1R gene (the main hair-colour gene). Today, there are 11 MC1R alleles in Europeans, 5 in East Asians, and 1 in Africans. Phenotypically, this diversification is confined to Europeans (the East Asian alleles differ little in their effects).

Meanwhile, at a completely different gene, the same diversification happened with eye colour.

This diversification of hair and eye colour seems to have occurred after 20,000 BP -- when ancestral East Asians split off from ancestral Europeans. That's a very short time frame.

Some kind of selection is responsible. There is no way you can put it all down to relaxation of selection for dark skin. Harding et al. (2000) investigated this scenario and found that the time to the most recent common ancestral hair colour would need to be about a million years, with the redhead alleles alone being c. 80,000 years old. Templeton (2002) came to a similar conclusion: if the cause were relaxation of selection, the current level of hair colour diversity would have taken 850,000 years to develop. Yet modern humans have been in Europe for only 35,000 years or so.

I should also add that the relationship between hair colour and skin colour is problematic. Some hair-colour alleles (notably for red hair) show a strong relationship with skin colour. Others show little or no relationship. Aside from the short time frame of this evolutionary scenario, I don't see how relaxed selection for dark skin, could have created the palette of hair and eye hues we see today.

And (bollocks!)women are not 'plain' without makeup. They're just marvellous.

Tod said...

Correction:-

The rate of right handedness is higher in women. The rate of right handedness reached an all time high in Britain around about 1900 according to Chis McManus

-----------------------------

If the consequence of hunter gatherers switching from meat to an agricultural diet is the skin getting lighter how can those Africans who are ancestral to everyone else ( ie the hunter gatherer Khoisan and Oromo) have lighter skin than African agriculturists.

The melanized skin of the agriculturalist Bantu speaking Africans ( ie Black Africans ) is not easily explained by UVA destruction of folic acid because hunter gatherers never evolved black skin. Moreover Black Africans' skin is very dark even on parts of the body where it has never been exposed to the sun which is very unlike the putatively 'black' Australian Aborigines who are hardly darker than many Europeans on skin that has not been exposed to the sun.

Ben10 said...

I'm jumping in the arena to say that ultimately, Human Evolution is about Evolution. Evolution is sometimes poorly explained by darwinian gradualism. Gould observed that Evolution seems like punctuated equilibrium and he opposed gradual modifications even in the Homo genus. Gould wrote a chapter about H. erectus who, according to him, didn't change physically nor in its techniques for a million years. Then, we also have Lamarck whose 'acquired modifications' could easily be reworked, or at least reworded, within a modern molecular biology framework. I will simplistically reframed Darwin as the 'Evolution with DNA' and Lamarck as 'Evolution with RNA'. All creatures get a set of DNA genes with predefined adaptations to the environment, but also an RNA-dependant adaptibility potential coded in this DNA. Individuals who show adaptibilty are individuals whose organs and RNA-dependant cellular functions can slightly change to better fit the environment. These individuals have higher survival chance. Sure, they don't transmit their adaptations straight with their RNA, but they transmit their adaptibility potential, possibly with another visible trait like skin color, and therefore they can be recognized and choosen by sexual partners for this desirable potential, even if they are just carriers (i.e, non-hunting white women in post glacial europe). In the genus Homo, RNA-dependant adaptibility must have translated into transmissible behavior, a purely Lamarckian mechanism which boosts evolution to the level that Gould theory implies.
I have no proof of that, but I tend to believe that these white skin variants who appeared in Europe must have shown some additional adaptibility that improved their chance of survival. Whether it's an improved immune system, being smarter or more resistant, it must have been something, not just the pretty white skin or blue eyes, and since they got plenty of vit. D already, it had nothing to do with the light level. My bet is on IQ but that could be something else.

MK said...

OT, but just came across a paper by Gregory Clark that seemed interesting. Reminded me of your paper Peter on genetic pacification in Rome.

'The Domestication of Man: the Social Implications of Darwin'

http://campus.usal.es/~revistas/Artefactos/pdfs/5465.pdf

Anonymous said...

Tod, from what I understand, you seem to be arguing against skin color being so dependent on sunlight. While true, I don't see the point of some of your crticisms when they mainly seemed aimed at just jablosnki. And why drum up the danes having such light skin and low tesosterone levels? You know they're not that much lighter than surrounding populations.

"Moreover Black Africans' skin is very dark even on parts of the body where it has never been exposed to the sun which is very unlike the putatively 'black' Australian Aborigines who are hardly darker than many Europeans on skin that has not been exposed to the sun. "

Well, skin color obviously isn't entirely tied to vitamin D and UV rays, but I find your comparisons spurious. Those with dark skin can also see darkened internal organs, roofs of the mouth, and even gums. It's probably just a pleitropic relationship. I don't know why they have lightened foot soles and palms, but that seems true for all dark skinned populations. I even see it in south asians.

And what parts of the aborigines are you reffering to?

On another note, Frost, how do you think the case of south asians (many, many of them are as dark as SS africans and many as dark as sudanese and senegambians) fits in with your work? I don't know too much about their marital cultures, but nothing about their appearance and biochemistry seems "masculinzed". And what about sudanese blacks? They're extremely dark yet don't seem as polygamous as other SS africans. For example:

"Marriage is one of the most important Nuer traditions, and is arranged by the families of the bride and groom. The Nuer believe in monogamy, but divorce is not unheard of, and is usually caused by a lack of children. If a woman does not produce children, a man can demand the return of the cattle he paid for the marriage and can send the woman back to her own village."

Peter Frost said...

Tod,

Good point!

Ben10,

Tu raisonnes mieux en allemand ...

MK,

The text sounds interesting, but your link doesn't seem to work.

Anon,

Please don't call me 'Frost'. Call me 'Peter' (or 'Dr. Frost' if you must).

South Asians are lighter-skinned than sub-Saharan Africans. Robins (1991, Table 7.1, 7.3) lists the skin reflectance data for both regions.
Skin reflectance (dominant wavelength = 545 nm)
India: 12.4 - 25.3 (%)
Africa (exc. Khoisans): 7.9 - 14.9 (%)

Robins, A.H. (1991). Biological Perspectives on Human Pigmentation. Cambridge University Press.

It is only in the southeastern states of India that one finds people who are as dark as the lightest sub-Saharan Africans. These populations are largely descended from people similar in appearance and social organization to relic groups like the Andaman Islanders and the Veddas. And yes, these groups practice polygyny.

Please provide a reference for your Nuer quote. It contradicts what I have read about the Nuer, e.g.,

"Among the Nuer, polygyny was not only more common but also apparently preferred by men as a sign of wealth or prestige. ... It was also used by Nuer men as a strategy to acquire children or increase the number of their children."

Stone, L. Kinship and Gender: An Introduction. p. 188.

Anonymous said...

"South Asians are lighter-skinned than sub-Saharan Africans."

On average, yes, but many, many- particularly in south india- are as dark, or even darker than prototypical SS africans.

"It is only in the southeastern states of India that one finds people who are as dark as the lightest sub-Saharan Africans."

That is completely ridiculous, to be blunt. I have seen manny particularly dark skinned south asians as far north as pakistan. And to say the ones who in the southeast, the "darkest ones", are only as dark as the lightest SS africans is also ridiculous. That would mean they're no darker than the khoisan. Have you seen photos of dravidians and similar populations?

"These populations are largely descended from people similar in appearance and social organization to relic groups like the Andaman Islanders and the Veddas. And yes, these groups practice polygyny."

If so, then they are quite culturally distinct regardless. Besides, the south asian populations don't have particularly high levels of testosterone and muscle mass and the like.

"Please provide a reference for your Nuer quote. It contradicts what I have read about the Nuer, e.g.,"

Sorry. Here it is: http://www.ancienthistoricalsociety.org/NuerTribe.html

ben10 said...

"Tu raisonnes mieux en allemand ..." c'est la langue de Goethe.

Anonymous said...

Also, Peter, I've never once gotten the impression that polygamy is so dominated by female choice of male mates. Why do you think this? How could it never be the other way around?

Anonymous said...

You give the impression of almost all forms of polygamy consisting of the kind you see among the wodaabe. (albeit they select for effeminate men) In the sense of men competing for the graces of a woman. You seldom seem to bespeak of a form of polygamy where men choose whomever they want, without competition that allows the permission of the woman.

Anonymous said...

Basically, a case of polygamy where men have a prime say- not the women.

MK said...

Sorry, here is the link again:

http://campus.usal.es/~revistas/Artefactos/pdfs/5465.pdf

Otherwise the pdf comes up just with a google search of the title.

'The Domestication of Man: the Social Implications of Darwin'

MK said...

The Domestication of Man

anorn said...

I'm the anon from earlier. I'll note that I've discussed the issue of skin color and beauty with you previously. I'll use the name "anorn" from now on.

Though back on topic. I'm not sure of the frequency of polygamy among sudanese blacks, who are extremely dark, so I'm probably not as informed as you are. Though the indices of polygamy among them aren't especially high, and most high rates of polygamy seem to cluster on the southern or western regions of sudan, quite removed from the nuer, dinka, nuba etc.

Peter Frost said...

"That would mean they're no darker than the khoisan."

I was excluding Khoisans (please reread my previous comment).

"Have you seen photos of dravidians and similar populations?"

I've known and worked with Tamils. They're as dark as lighter-skinned sub-Saharan Africans. They never have the deep black color one finds in Senegambia or southern Sudan.

"If so, then they are quite culturally distinct regardless."

Yes, they are. So what? My point was that South Asians, particularly in the southeastern states, are partly descended from a population whose physical and behavioral characteristics were similar to those of the hunter-gatherer/early agricultural peoples of south and southeast Asia (e.g., Andaman Islanders, Veddas, Papuans, Australians Aborigenes, etc.). These peoples were characterized by a high incidence of polygyny and a more robust body type.

With the rise of a more advanced agrarian society in India, characterized by State formation and social stratification, a new set of selection pressures came into being, including selection for submission and reduced aggressiveness, i.e., genetic pacification.

If you do a Google search for 'genetic pacification' you'll find earlier posts that I've written on that subject.

"Also, Peter, I've never once gotten the impression that polygamy is so dominated by female choice of male mates. Why do you think this?"

Polygny increases both female choice and male-male competition for mates. Increase in male robustness is probably due to the second factor.

"most high rates of polygamy seem to cluster on the southern or western regions of sudan, quite removed from the nuer, dinka, nuba etc."

The HRAF classifies these peoples as practicing "general polygyny", i.e., most married women are in polygnyous households.

Peter Frost said...

MK,

Thanks!

anorn said...

"I've known and worked with Tamils. They're as dark as lighter-skinned sub-Saharan Africans. They never have the deep black color one finds in Senegambia or southern Sudan."

I understand your distinction now, but there's very significant overlap, and some are indeed as dark as those populations, even ones as far as pakistan. For example:

http://i28.tinypic.com/2m5ey4h.jpg
http://i28.tinypic.com/21ci7g9.jpg

And these are just snapshots of the diversity among them:

http://i27.tinypic.com/2hxt2yv.jpg
http://nl.tinypic.com/r/ih8uxg/3
http://i27.tinypic.com/2rykc50.jpg

As dark as the lightest ones perhaps, but that says markedly little of the variation.

"Yes, they are. So what? My point was that South Asians, particularly in the southeastern states, are partly descended from a population whose physical and behavioral characteristics were similar to those of the hunter-gatherer/early agricultural peoples of south and southeast Asia (e.g., Andaman Islanders, Veddas, Papuans, Australians Aborigenes, etc.). These peoples were characterized by a high incidence of polygyny and a more robust body type."

It's relevant because their skin color is so dark in spite of those cultural practices being lifted long, long ago, with hindu cultural practices and the like being dominant for millenia. Nor is their physique so masculine. Going by your map in "Sexual Selection and Human Geographic Variation", the frequencies of polygamy are quite low in southern india and for south asia in general. Are the especially dark populations like the andamanese as polygamous as senegambians and sahelians?

"With the rise of a more advanced agrarian society in India, characterized by State formation and social stratification, a new set of selection pressures came into being, including selection for submission and reduced aggressiveness, i.e., genetic pacification."

anorn said...

This didn't lighten their skin color, however. I also disagree with this interpretation of the state civilizing people. The rise of organized societies only really seemed to make basic societal violence less common, not violence as a whole. This is well attested to by the extraordinary levels of violence people exhibited in terms of war, in the sense of butchering massive amounts of civilians in vicious manners with basic melee weaponry: http://www.hawaii.edu/powerkills/DBG.CHAP3.HTM

In your first post on genetic pacification, you focus on Clarke's work. Does Clarke argue all, or just most of the change in britain back then was due to differential breeding among social classes? You also mention how many have critiqued him for not explaining how these changes spread so easily to the rest of the world, yet say that the same behavior evolution happened among them. I find it astoundingly hard to believe that markedly similar forms of differential breeding happened so similarly throughout all of europe just as it did in the UK, if that is what you are implying.

"Polygny increases both female choice and male-male competition for mates. Increase in male robustness is probably due to the second factor."

But that's the thing- you give the impression of almost all forms of polygamy consisting of female choice, in the sense of women choosing which men they'll marry. Do forms of polygamy where men have the final say exist at such lower frequencies?

"The HRAF classifies these peoples as practicing "general polygyny", i.e., most married women are in polygnyous households."

Well, I myself don't think monogamy dominates in sudan, but I get the impression of polygamy being less frequent among them compared to other SS african populations. Your argument of polygamy accounting for so much of human skin color variation due to aesthetic preferences in skin color seems very loose and rough. The map you cite in your paper seems too narrow as well- other skin color maps show much finer different gradients:

http://tinyurl.com/r8eeoh
http://tinyurl.com/2awphdp

On another note, what do you know of polygamy among aborigines?

Peter Frost said...

"some are indeed as dark as those populations"

Then we'll have to agree to disagree. What you call 'deep black' is what I would call 'brown'.

If one makes allowance for repeated migrations from the Middle East and Cental Asia, and also variation by caste, South Asian skin color would largely reflect conditions that existed prior to State formation.

You seem to feel that the rise of the State should have lightened mean skin color. Or perhaps you feel I feel that way. (I don't). Or perhaps you're not really sure what you mean when you write.

"I find it astoundingly hard to believe that markedly similar forms of differential breeding happened so similarly throughout all of europe just as it did in the UK, if that is what you are implying."

Then you know astoundingly little about medieval and post-medieval Europe. The higher reproductive success of the upper and middle classes was a widespread phenomenon throughout Western Europe until the late 19th century.

"The rise of organized societies only really seemed to make basic societal violence less common, not violence as a whole."

Then where do we disagree? Violence did not become less common. It became a State monopoly.

anorn said...

"You seem to feel that the rise of the State should have lightened mean skin color. Or perhaps you feel I feel that way. (I don't). Or perhaps you're not really sure what you mean when you write."

The existence of the state has been around for thousands of years in south asia and many other places. The general polygamy you allude to that exists among isolated south asian populations like veddahs and andaman islanders hasn't been in place in south india and south asia for a long time. Under your theories, why wouldn't a drop in polygamy lighten skin color over thousands of years?

"Then you know astoundingly little about medieval and post-medieval Europe. The higher reproductive success of the upper and middle classes was a widespread phenomenon throughout Western Europe until the late 19th century."

This isn't about just europe, it's europe as a whole, or anywhere else that industrialization has come relatively easily. Did this kind of social mobility happen so linearly and similarly over such similar timespans across much of the world?

And is Clarke arguing that the principal component for behavioral change was differential breeding?

"Then where do we disagree? Violence did not become less common. It became a State monopoly."

Eh, I guess you're right. Sorry about jumping to conclusions.

Peter Frost said...

"Under your theories, why wouldn't a drop in polygamy lighten skin color over thousands of years?"

My argument is that the mean skin color of a population will change relatively fast only in response to strong sexual selection (a highly skewed operational sex ratio). If the sex ratio becomes unskewed (e.g., through a reduction of polygyny), there will simply be a reduction of sexual selection and a relative increase in the importance of natural selection.

Natural selection (vitamin-D insufficiency, skin cancer, sunburn) acts very slowly on human skin color, except at the extremes of human pigmentation, e.g., a very light population that has migrated to the tropical zone. This was the finding of Brace, C.L., Henneberg, M., & Relethford, J.H. (1999). Skin color as an index of timing in human evolution. American Journal of Physical Anthropology, 108 (supp. 28), 95-96.

"This isn't about just europe, it's europe as a whole, or anywhere else that industrialization has come relatively easily."

No. In much of the world, polygyny used to cause continual gene flow from the lower classes (or foreign sources) into the upper class. In many societies, there was no well defined upper class that could perpetuate itself over many centuries. It would be destroyed after a century or so of power, and the process would start over. Or there were just "big men" who would come and go.

Anonymous said...

Thanks for the clarification on India. However, what do you know of the rates of polygamy among the more ancestral populations in those regions? The andamanese are one of the single darkest populations on the planet.

And what of polygamy among aborigines and sudanese blacks?

"No. In much of the world, polygyny used to cause continual gene flow from the lower classes (or foreign sources) into the upper class. In many societies, there was no well defined upper class that could perpetuate itself over many centuries. It would be destroyed after a century or so of power, and the process would start over. Or there were just "big men" who would come and go."

My point, in relation to Clarke's work, doesn't seem to have anything to do with this. Clarke seems to argue- and you as well- that the upper classes in western europe had much greater fertility and proliferated throughout the lower classes. My point of contention was that this should seemingly occur throughout all of europe and much of the rest of the world.

anorn said...

Also, a quick note- I apologize for asking if you've ever even seen photos of southern indians. You obviously have, but your comment struck me as odd.

Anonymous said...

"It is only in the southeastern states of India that one finds people who are as dark as the lightest sub-Saharan Africans. These populations are largely descended from people similar in appearance and social organization to relic groups like the Andaman Islanders and the Veddas. And yes, these groups practice polygyny."

Wrong.

http://books.google.com/books?id=M_47kfxz4ogC&pg=PA22&lpg=PA22&dq=andaman+polygamy&source=bl&ots=7cWk8dDibX&sig=hSiCQNgPNZ5tuybfEJagTMd36p4&hl=en&sa=X&ei=l1YzVIDRNe-TsQTzqoAw&ved=0CCYQ6AEwAQ#v=onepage&q=polygamy&f=false

Anonymous said...

And here's one for the Veddah: http://books.google.com/books?id=GaNIrttDUY0C&pg=PA61&dq=andaman+polygamy&hl=en&sa=X&ei=0pYzVJONIuHL8AGR2oCYBw&ved=0CCEQ6AEwATgK#v=onepage&q=andaman%20polygamy&f=false

You have scarcely mentioned these groups in your writings. I guess it's because they're inconvenient for you.

Anonymous said...

The biggest people in south asia and maybe the world are the Jatt Sikhs who can even reach 7 ft + in height