Friday, July 30, 2010

The Roman State and Genetic Pacification

The online journal Evolutionary Psychology has published my article “The Roman State and genetic pacification.” The following is the abstract:

Over the last 10,000 years, the human genome has changed at an accelerating rate. The change seems to reflect adaptations to new social environments, including the rise of the State and its monopoly on violence. State societies punish young men who act violently on their own initiative. In contrast, non-State societies usually reward such behavior with success, including reproductive success. Thus, given the moderate to high heritability of male aggressiveness, the State tends to remove violent predispositions from the gene pool while favoring tendencies toward peacefulness and submission.

This perspective is applied here to the Roman state, specifically its long-term effort to pacify the general population. By imperial times, this effort had succeeded so well that the Romans saw themselves as being inherently less violent than the “barbarians” beyond their borders. By creating a pacified and submissive population, the empire also became conducive to the spread of Christianity—a religion of peace and submission. In sum, the Roman state imposed a behavioral change that would over time alter the mix of genotypes, thus facilitating a subsequent ideological change.

Please feel free to offer your comments.

Frost, P. (2010). The Roman State and genetic pacification, Evolutionary Psychology, 8(3), 376-389,

Thursday, July 22, 2010

A strange story

Eboracum with the Colonia in the foreground and the fortress across the river.

In my last two posts, I presented evidence that Roman York (Eboracum) was home to a large African community in the late 300s. This was due to the stationing of Nubian archers and other African legionnaires in this and other garrison towns of northern England.

Did many remain after the end of Roman rule c. 400? By then, the legions had been largely pulled out and redeployed elsewhere in the dying empire. So the African legionnaires were certainly fewer in number. But these pullouts did not affect the veterans, who were already settled on local estates with their families. Among these ‘Afro-British’ settlers, valued skills like archery would have been passed down from father to son, thus making their community a key player during increasingly troubled times...

What happened after the end of Roman rule? Did this community survive into sub-Roman times? This is the period that began with the last pullout of Roman troops c. 400 and ended with the collapse of Romano-British society in the late 500s.

The historical sources are not entirely mute on this question. These sources, however, have been corrupted by the passage of time. There is also the human temptation to embellish the facts and tell a good story. This is especially so for the sub-Roman period, when many written records were destroyed and when writing itself became almost a lost art. Historical accounts survived only in oral form before being later written down, often much later.

The source that most interests us is the Historia Regum Britanniae (c. 1136), purportedly a translation of an old Welsh chronicle. It is largely consistent with earlier works on British history, like the Historia Britonum (9th-century), the Historia ecclesiastica gentis Anglorum (8th century), and the De Excidio et Conquestu Britanniae (6th century). On the other hand, many of its passages seem too outlandish to be true.

One passage, for instance, reports that over a hundred thousand Africans took part in the struggles between the Romano-British and the Anglo-Saxons:

The Saxons, having had experience of his [the British ruler’s] shiftiness, went unto Gormund, King of the Africans, in Ireland, wherein, adventuring thither with a, vast fleet, he had conquered the folk of the country. Thereupon, by the treachery of the Saxons, he sailed across with a hundred and sixty-six thousand Africans into Britain, which in one province the Saxons by perjuring their oath of fealty, and in another the Britons by continually carrying on civil wars amongst themselves, were utterly laying waste.

Entering into covenant, therefore, with the Saxons, Gormund made war upon Careticus, and after many battles betwixt them, drove him fleeing from city unto city until he forced him into Cirencester and did there beleaguer him.

[…] When Gormund at last had taken and burnt the said city, he did battle with Careticus and drove him fleeing beyond the Severn into Wales. Then he desolated the fields, set fire to all the neighbouring cities, nor did he stint his fury until he had burnt up well-nigh the whole face of the country from sea to sea; in such sort that all the colonies were battered to the ground by rams, and all they that dwelt therein along with the priests of the churches delivered up to the flashing of their swords or the crackling of the flames.

[… after] the tyrant of evil omen had laid waste, as hath been said, well-nigh the whole island with his countless thousands of Africans, the more part thereof which was called Loegria did he make over unto the Saxons through whose treachery he had come into the land. The remnant of the Britons did therefore withdraw them into the western parts of the kingdom, Cornwall, to wit, and Wales […]

Historia Regum Britanniae 11:8-10

If we exclude the African subplot, this story is consistent with other historical accounts, i.e., the Romano-British state fell because of internal dissensions and because the Anglo-Saxons had renewed their war of conquest after a half-century of vassalage.

But did these warring factions recruit soldiers from an African state in Ireland? No such state is described in any other account. On the other hand, the chronicler may have confused Hibernia (Ireland) with Eboracum (York)—the old garrison town where many African legionnaires had once been stationed. The two place names are especially similar if we remember that Eboracum would have been shortened to Ebora in late Latin.

Initially, these Africans may have hired themselves out to opposing Romano-British factions. Then, with the renewal of the Anglo-Saxon invasion, it is possible that many of them defected to that side, having seen which way the wind was turning. Perhaps this mass defection was decisive. Or perhaps the Welsh chronicler needed a scapegoat.

Anyhow, there is no doubt about the final outcome: the Romano-British state collapsed under conditions probably as dramatic as those described above. And it is certainly plausible that some soldiers switched sides. These were chaotic times when people had to live by their wits. In this, the Afro-British were probably no worse than others.

Did their community last into Anglo-Saxon times? This is doubtful. Even without the carnage of war, their numbers would have steadily declined, partly because of the below-replacement fertility that prevailed throughout the Roman Empire and partly because of the 6th-century plagues that carried off one in three people. There was also assimilation: beyond a certain point, successive intermarriage would have led to many individuals passing into the broader Romano-British society.

And, of course, there was the carnage of war. As soldiers, the Afro-British would have suffered many casualties. As civilians, they would have been caught up in the widespread destruction of the late 500s.

If this community did survive into Anglo-Saxon times, there would surely have been some mention by the
Venerable Bede [672-735], a prolific Christian writer who lived in Northumbria and often visited York. Yet he made no reference to them.

Or maybe he did. In his commentary on the book of Genesis, he comes down hard on Nimrod, who is often identified by Christian and Jewish commentators as a black African (because his father was Cush):

Genesis 10:8-9a Now Cush begot Nimrod. He began to be mighty on the earth, and he was a stout hunter before the Lord.
While the descendants of Shem and of Japheth remained in the innocence of a life of honesty, there arose from the cursed offspring of Ham one who corrupted the condition of the human way of life by a new kind of living. So long as he was puffed up by his remarkable power, he at first lived by hunting; then, having gathered an army, he strove to exert an unaccustomed tyranny upon the peoples. […]

10:9b From this came a proverb: Like Nimrod a stout hunter before the Lord.
It was turned into a proverb because unaccustomed deeds were done in his times. And the additional phrase, before the Lord, is for the sake of magnifying the outrage, namely that it was totally rash and arrogant that a man should dare to live in such a way on earth ‘before the Lord’.

But then why didn’t Bede mention these Afro-British in his Ecclesiastical History of the English People (Historia ecclesiastica gentis Anglorum)? Perhaps there was a reason for not mentioning them. He had sent an earlier draft to Ceolwulf, king of Northumbria, and asked for the king’s approval. If there had been an alliance between the Anglo-Saxons and Eboracum, Ceolwulf’s family would have been directly involved...

We will never know the full story. (It’s not for nothing that this period is called the Dark Ages). It’s likely that when Roman rule ended c. 400, power fell into the hands of a number of regional entities, including one centered on Eboracum. These entities gradually consolidated to fight the Anglo-Saxon invasion, eventually becoming a single kingdom under a charismatic leader, the semi-mythical “King Arthur.” This leader reduced the Anglo-Saxons to vassalage c. 500, thus bringing about a half-century of peace. Then, after his death c. 550, the Romano-British kingdom split up into warring factions. The Anglo-Saxons seized the opportunity and allied themselves with one or more of the losing factions, including the Afro-British warlords based at Eboracum.

It was an alliance that the Anglo-Saxons lived to regret, apparently because of “unaccustomed deeds.” Perhaps the African soldiers plundered not only Romano-British civilians but also those Anglo-Saxons who had remained in vassalage. Who knows? All we really know, based on archeological evidence, is that Eboracum became uninhabited at some point in the late 500s. And so ends a strange story.


Geoffrey of Monmouth. (1904) Histories of the Kings of Britain (Historia Regum Britanniae), transl. by Sebastian Evans

Venerable Bede. (2008). On Genesis, transl. by C.B. Kendall, Liverpool University Press.

Friday, July 16, 2010

An African community in Roman Britain?

Figurines of Nubian archers (from Egypt)

The Roman conquest of Britain brought not only cultural change but also profound ethnic change, i.e., an influx of soldiers, officials, and traders from elsewhere. Until recently, historians placed this influx mainly in the first century of Roman rule. As the native British became Romanized, they would have increasingly filled local positions in the army and the administration. This view now appears to be erroneous: the process of ethnic replacement continued unabated and may have even intensified. In particular, the last century of Roman rule saw many soldiers arrive from North Africa and sub-Saharan Africa.

Leach et al. (2010) argue that the north of England, with its many garrison towns, became heavily multi-ethnic through the stationing of foreign soldiers and the subsequent settlement of veterans on local estates:

Inscriptions from York attest to the presence of Gauls, Italians and a possible Egyptian at York, although much of the epigraphic evidence is significantly earlier than the burial discussed here (Ottaway 2004). Artefactual evidence also suggests that ‘the Roman north was a cosmopolitan place with a great mixing of people from all over the empire’ (Cool 2002: 42). For example, Swan (1992) argued for the presence of North Africans in York on the basis of braziers and other vessels typical of North African food-ways but made in local fabrics.

Previous studies of the physical remains of the people of Eboracum (Buxton 1935; Warwick 1968) suggested that the males exhibited heterogeneous craniomorphometric traits suggesting migration from a variety of geographic locales. However, both argued that the female population of Roman York was indigenous. In their view, the diversity noted in the female crania represented genetic admixture between local women and migrant males
(Warwick 1968: 155).

Leach et al. (2009) provide evidence for intense foreign settlement. At one burial ground near Roman York, craniometric analysis revealed that 66% of the individuals clustered most closely with Europeans, 23% with sub-Saharan Africans, and 11% with Egyptians. At another, the proportions were 53% European, 32% sub-Saharan, and 15% Egyptian (Leach et al., 2009).

In a subsequent article, Leach et al. (2010) focus on one burial: a young woman 18 to 23 years old who had been buried between 350 and 400 AD. The authors dubbed her the ‘Lady of York’ because of her stone coffin and its rich array of grave goods, apparently a sign of high status. Nonetheless, her skull showed little or no affinity to any European population, the closest match being a sample of African-American women. Various facial indices showed a mix of sub-Saharan African and European traits, suggesting a person of mixed parentage or perhaps a North African. An African origin is also suggested by the presence of elephant ivory among the grave goods. The authors conclude that this burial “contradicts assumptions that may derive from more recent historical evidence, namely that immigrants are low status and male, and that African individuals are likely to have been slaves.”

Undoubtedly, many Africans rose to high positions in the Roman army. This was especially so for the Nubians, who were prized for their skills in archery. This being said, the Nubians came from the Egyptian culture area and, as such, attached great importance to human burial. In comparison to Europeans of the same socioeconomic status, they would have been more inclined to provide grave goods and to use tombs made from impervious materials.

High status is also inconsistent with a Latin inscription placed in the coffin: SOR AVE VIVAS IN DEO [Sister, hail, live in God]. This is Vulgar Latin, the kind used by the lower classes. An educated citizen would have inscribed the more classical soror instead of sor, especially in the formal context of a burial.

An African community in Roman Britain?

Leach et al. (2010) conclude that the Romans laid “the foundation of a multicultural and diverse community.”

The word ‘foundation’ suggests permanence and is perhaps inappropriate. If the Lady of York had lived a full life, she would have seen the end of Roman Britain—less than a half century later. She would have certainly witnessed the pullout of the legions and, perhaps, the arrival of the Dark Ages … with the breakdown of law and order after 430.

What happened to her community? Did it play a role in the struggles between the Romano-British and the Anglo-Saxons? Did it survive into the early Anglo-Saxon period?

I will try to answer these questions in my next post. For now, let me ponder another question: why had Roman Britain been so intensely militarized? More legions were stationed there than in Lower Germany, which was closer to the Empire’s core and faced a much larger barbarian population. If Britain had been ruled indirectly, through client states, the Romans would have been free to concentrate more soldiers along the crucial Rhine-Danube border.

These questions have answers … more or less. The Empire had annexed Britain during the early days of seemingly endless expansion, when military leaders worried much less about spreading themselves too thin. Britain was also a Celtic homeland. Its people were closely related to those of Gaul and had openly sympathized with them during the rebellion led by Vercingetorix. Even as a collection of client states, Britain would have remained a threat to Roman rule in Gaul. Finally, more legions were needed in Britain because the barbarians to the north (Scots and Picts) were less interested in being friends of Rome than those along the frontier of continental Europe.

Well, perhaps. In any case, history would have turned out the same either way. The main barbarian threat—the one that led to the sack of Rome in 410—came not from the barbarians outside the Empire but from those who had been allowed to settle within. This was an eventuality that Roman military strategists had never foreseen and for which they were unprepared. When the end came, the border fortifications proved to be of no help.


Leach, S., H. Eckardt, C. Chenery, G. Müldner, & M. Lewis. (2010). A Lady of York : migration, ethnicity and identity in Roman Britain, Antiquity, 84, 131-145.

Leach, S., M. Lewis, C. Chenery, G. Müldner, & H. Eckardt. (2009). Migration and diversity in Roman Britain: A multidisciplinary approach to the identification of immigrants in Roman York, England, American Journal of Physical Anthropology, 140, 546-561

P.S. The link and reference information for my 2008 article have changed. They are now:

Frost, P. (2008). Sexual selection and human geographic variation, Special Issue: Proceedings of the 2nd Annual Meeting of the NorthEastern Evolutionary Psychology Society. Journal of Social, Evolutionary, and Cultural Psychology, 2(4), pp. 169-191.

Friday, July 9, 2010

Just who were the Romano-British?

The Anglo-Saxons ‘conquered’ the Civil Zone (non-shaded part of England), where the departing Roman army left a social and demographic vacuum. From W.E. Lunt's History of England

What happened to the Romano-British? Were they wiped out by the Anglo-Saxons? Or were they absorbed by their conquerors?

Razib Khan discusses the latest answer to this question. O'Dushlaine et al. (2010) used three genetic datasets:

1. A sample from Dublin, Ireland to represent the now extinct Romano-British.

2. A sample from Sweden to represent the Anglo-Saxons.

3. A sample from south and southeastern England to represent present-day English people.

Results: the English subjects were genetically closer to the Irish subjects than to the Swedish subjects. Conclusion: present-day English people are largely descended from the Romano-British. There was no ethnic cleansing.

Uh, not so fast. As Razib and his commenters point out, the Anglo-Saxons came not from Sweden but from what is now the Netherlands, northwest Germany, and southern Denmark. Frisians would probably be a closer match. Also, Dubliners inhabit an area of substantial Viking and English settlement. They too would be a lousy proxy for the Celtic inhabitants of Roman Britain.

But there’s another problem. A more basic one. How Celtic were the Romano-British? We know they had ceased to be Celtic linguistically.

After A.D. 43, Latin advanced rapidly. No Celtic inscription occurs, I believe, on any monument of the Roman period in Britain, neither cut on stone nor scratched on tile or potsherd, and this fact is the more noteworthy because, as I shall point out below, Celtic inscriptions are not at all unknown in Gaul. […]

The town site that we can best examine for our present purpose is Calleva or Silchester, ten miles south of Reading, which has been completely excavated with care and thoroughness. Here a few fairly complete inscriptions on stone have been discovered, and many fragments of others, which prove that the public language of the town was Latin. […]

In the twenty years' excavation of the site, no Celtic inscription has emerged. Instead, we have proof that the lower classes wrote Latin for all sorts of purposes. Had they known Celtic well, it is hardly credible that they should not have sometimes written in that language, as the Gauls did across the Channel. A Gaulish potter of Roman date could scrawl his name and record, Sacrillos avot, 'Sacrillus potter', on the outside of a mould. No such scrawl has ever been found in Britain. The Gauls, again, could invent a special letter Eth to denote a special Celtic sound and keep it in Roman times. No such letter was used in Roman Britain, though it occurs on earlier British coins. This total absence of written Celtic cannot be a mere accident. (Haverfield, 1912, pp. 10-12)

To a large degree, the Romano-British also ceased to be Celtic ethnically. This has been suspected on the basis of unusual burial objects and epigraphic inscriptions that record the presence of individuals from throughout the Roman Empire. Many came with the Roman army, as shown by fieldwork in Roman York—a town with a large garrison. At one burial ground, craniometric analysis revealed that 66% of the individuals clustered most closely with Europeans, 23% with sub-Saharan Africans, and 11% with Egyptians. At another, the proportions were 53% European, 32% sub-Saharan, and 15% Egyptian (Leach et al., 2009).

Britain was the most heavily militarized region of the Roman Empire. As such, it bore the full brunt of Romanization via the stationing of imperial troops and their demographic impact (associated influx of Roman officials, traders, etc., settlement of veterans, fathering of children with native women). This was especially so in the ‘Civil Zone’ of the south and the east, where the legions were garrisoned and where veterans usually settled after their years of service.

In the second century A.D., Britain had a garrison of ca. 50,000 men, comprised of three legions (with fortresses at Caerleon, Chester, and York) and a huge force of auxiliary troops. This army of occupation, variously estimated at between 10 and 12 percent of the entire imperial army, is a key distinguishing characteristic of Roman Britain, being by far the heaviest density of troops for a comparable area of territory. (Mattingly, 2000)

Native Celtic society was extinguished in the Civil Zone. It was submerged by a foreign military presence—like the impact of U.S. bases on certain Pacific islands. Thus, the Anglo-Saxons did not replace a native Celtic population. To some extent, they actually restored the status quo ante.

This conclusion leads to others. Wales and Cornwall are Celtic today because their inhabitants remained so during the Roman occupation. These regions fell within the Military Zone and became Romanized to a much lesser degree. In contrast, the Civil Zone developed into an atomized society of diverse origins where the main organizing principle was the Roman army. When the army withdrew in the early 5th century, Romano-British society imploded—a decline made all the worse by below-replacement fertility and 6th-century plagues that killed three out of ten people.

There is no need to postulate a process of ethnic cleansing. Once the plug had been pulled, the death of Roman Britain became inevitable.


Haverfield, F. (1912) The Romanization of Roman Britain, Second Edition, Oxford at the Clarendon Press.

Khan, R. (2010). The English & Irish together again. Discover Gene Expression, June 24

Leach, S., M. Lewis, C. Chenery, G. Müldner, & H. Eckardt. (2009). Migration and diversity in Roman Britain: A multidisciplinary approach to the identification of immigrants in Roman York, England, American Journal of Physical Anthropology, 140, 546-561.

Mattingly, D.J. (2000). Roman Britain - Military Aspects, Administration and Government, Towns, Countryside, Religion, Culture, and Economy, vallum, civitates, civitas

O'Dushlaine, C.T., D. Morris, V. Moskvina, G. Kirov, International Schizophrenia Consortium, M. Gill, A. Corvin, J.F. Wilson, and G.L. Cavalleri. (2010). Population structure and genome-wide patterns of variation in Ireland and Britain, European Journal of Human Genetics, advance online publication.

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.


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

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. (visited on July 10, 2008).

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