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The genetic causes, ethnic origins and history of red hair

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What causes red hair ?

Red hair is a recessive genetic trait caused by a series of mutations in the melanocortin 1 receptor (MC1R), a gene located on chromosome 16. As a recessive trait it must be inherited from both parents to cause the hair to become red. Consequently there are far more people carrying the mutation for red hair than people actually having red hair. In Scotland, approximately 13% of the population are redheads, although 40% carry at least one mutation.

There are many kinds of red hair, some fairer, or mixed with blond ('strawberry blond'), some darker, like auburn hair, which is brown hair with a reddish tint. This is because some people only carry one or a few of the several possible MC1R mutations. The lightness of the hair ultimately depends on other mutations regulating the general pigmentation of both the skin and hair.

Red Hair Facts

  • Skin and hair pigmentation is caused by two different kinds of melanin: eumelanin and pheomelanin. The most common is eumelanin, a brown-black polymer responsible for dark hair and skin, and the tanning of light skin. Pheomelanin has a pink to red hue and is present in lips, nipples, and genitals. The mutations in the MC1R gene imparts the hair and skin more pheomelanin than eumelanin, causing both red hair and freckles.
  • Redheads have very fair skin, almost always lighter than non-redheads. This is an advantage in northern latitudes and very rainy countries, where sunlight is sparse, as lighter skin improves the absorption of sunlight, which is vital for the production of vitamin D by the body. The drawback is that it confers redheads a higher risk for both sunburns and skin cancer.
  • Studies have demonstrated that people with red hair are more sensitive to thermal pain and also require greater amounts of anesthetic than people with other hair colours. The reason is that redheads have a mutation in a hormone receptor that can apparently respond to at least two different hormones: the melanocyte-stimulating hormone (for pigmentation) and endorphins (the pain relieving hormone).
  • Folk wisdom has long described redheads as hot-tempered and short-tempered.
  • If you did an autosomal DNA test (e.g. with 23andMe), you can check if you carry some of the MC1R mutations.

Red hair, a Celto-Germanic trait ?

Red hair has long been associated with Celtic people. Both the ancient Greeks and Romans described the Celts as redheads. The Romans extended the description to Germanic people, at least those they most frequently encountered in southern and western Germany. It still holds true today.

Although red hair is an almost exclusively northern and central European phenomenon, isolated cases have also been found in the Middle East, Central Asia (notably among the Tajiks), as well as in some of the Tarim mummies from Xinjiang, in north-western China. The Udmurts, an Uralic tribe living in the northern Volga basin of Russia, between Kazan and Perm, are the only non-Western Europeans to have a high incidence of red hair (over 10%). So what do all these people have in common ? Surely the Udmurts and Tajiks aren't Celts, nor Germans. Yet, as we will see, all these people share a common ancestry that can be traced back to a single Y-chromosomal haplogroup: R1b.

Where is red hair more common ?

It is hard to calculate the exact percentage of the population having red hair as it depends on how wide a definition one adopts. For example, should men with just partial red beards, but no red hair on the top of their heads be included or not ? Should strawberry blond be counted as red, blond, or both ? Regardless of the definition, the frequency of red hair is highest in Ireland (10 to 30%) and Scotland (10 to 25%), followed by Wales (10 to 15%), Cornwall and western England, Brittany, the Franco-Belgian border, then western Switzerland, Jutland and southwest Norway. The southern and eastern boundaries, beyond which red hair only occurs in less than 1% of the population, are northern Spain, central Italy, Austria, western Bohemia, western Poland, Baltic countries and Finland.

Overall, the distribution of red hair matches remarkably well the ancient Celtic and Germanic worlds. It is undeniable too that the highest frequencies are always observed in Celtic areas, especially in those that remained Celtic-speaking to this day or until recently. The question that inevitably comes to many people's minds is: did red hair originate with the Celtic or the Germanic people ?

Southwest Norway may well be the clue to the origin of red hair. It has been discovered recently, thanks to genetic genealogy, that the higher incidence of both dark hair and red hair (as opposed to blond) in southwest Norway coincided with a higher percentage of the paternal lineage known as haplogroup R1b-L21, including its subclade R1b-M222, typical of northwestern Ireland and Scotland (the so-called lineage of Niall of the Nine Hostages). It is now almost certain that native Irish and Scottish Celts were taken (probably as slaves) to southwest Norway by the Vikings, and that they increased the frequency of red hair there.

Map of red hair frequency in Europe

Distribution of haplogroup red hair in Europe

Map of Y-haplogroup R1b in Europe

Distribution of haplogroup R1b in Europe

       

The 45th parallel, a natural boundary for red hair ?

What is immediately apparent to genetic genealogists is that the map of red hair correlates with the frequency of haplogroup R1b in northern and western Europe. It doesn't really correlate with the percentage of R1b in southern Europe, for the simple reason that red hair is more visible among people carrying various other genes involved in light skin and hair pigmentation. Mediterranean people have considerably darker pigmentations (higher eumelanin), especially as far as hair is considered, giving the red hair alleles little opportunity to express themselves. The reddish tinge is always concealed by black hair, and rarely visible in dark brown hair. Rufosity being recessive, it can easily stay hidden if the alleles are too dispersed in the gene pool, and that the chances of both parents carrying an allele becomes too low. Furthermore, natural selection also progressively pruned red hair from the Mediterranean populations, because the higher amount of sunlight and strong UV rays in the region was more likely to cause potentially fatal melanoma in fair-skinned redheads.

At equal latitude, the frequency of red hair correlates amazingly well with the percentage of R1b lineages. The 45th parallel north, running through central France, northern Italy and Croatia, appears to be a major natural boundary for red hair frequencies. Under the 45th parallel, the UV rays become so strong that it is no longer an advantage to have red hair and very fair skin. Under the 41th parallel, redheads become extremely rare, even in high R1b areas.

The 45th parallel is also the traditional boundary between northern European cultures, where cuisine is butter-based, and southern European cultures, preferring olive oil for cooking. In France, the 45th parallel is the also limit between the northern Ol dialects of French and the southern Occitan language. In northern Italy, it is the 46th parallel that separates German speakers (in South Tyrol) from Italian speakers. The natural boundary probably has a lot to do with the sun and climate in general, since the 45th parallel is exactly halfway between the Equator and the North Pole.

Even as far back as Neolithic times, the 45th parallel roughly divided the Mediterranean Cardium Pottery culture from the Central European Linear Pottery culture. It is entirely possible, and even likely, that the European north-south divide, not just for culture and agriculture, but also for phenotypes and skin pigmentation, go back to Neolithic times, when the southern expansion of agriculture was carried out mostly by the migration of farmers from the Near East to Iberia, following the Mediterranean coastlines, while the northern Danubian diffusion of farming was achieved by native Mesolithic Europeans who acquired Neolithic techniques by contact with farmers from Thessaly and Albania (Sesklo culture), and only blending to a small extent.

Slavic, Baltic and Finnish people are predominantly descended from haplogroup R1a, N1c1 and I1. Their limited R1b ancestry means that the MC1R mutation is much rarer in these populations. This is why, despite their light skin and hair pigmentation and living at the same latitude as Northwest Europeans, almost none of them have red hair, apart from a few Poles or Czechs with partial German ancestry.

Where did red hair first arise ?

It has been suggested that red hair could have originated in Paleolithic Europe, especially since Neanderthal also had red hair. The only Neanderthal specimen tested so far (from Croatia) did not carry the same MC1R mutation responsible for red hair in modern humans (the mutation in question in known as Arg307Gly). But since Neanderthals evolved alongside Homo Sapiens for 600,000 years, and had numerous subspecies across all Europe, the Middle East and Central Asia, it cannot be ruled out that one particular subspecies of Neanderthal passed on the MC1R mutation to Homo Sapiens. It is however unlikely that this happened in Europe, because red hair is conspicuously absent from, or very low in parts of Europe with the highest percentages of haplogroup I (e.g. Finland, Bosnia, Sardinia) and R1a (Eastern Europe), the only two lineage associated with Mesolithic and Paleolithic Europeans. We must therefore look for the source of red hair, elsewhere. unsurpisingly, the answer lies with the R1b people - thought to have recolonised Central and Western Europe during the Bronze Age.

The origins of haplogroup R1b are complex, and shrouded in controversy to this day. The present author favours the theory of a Middle Eastern origin (a point upon which very few population geneticists disagree) followed by a migration to the North Caucasus and Pontic Steppe, serving as a starting point for a Bronze-age invasion of the Balkans, then Central and Western Europe. This theory also happens to be the only one that explains the presence of red hair among the Udmurts, Central Asians and Tarim mummies.

A possible Neanderthal link ?

Haplogroup R1b probably split from R1a during the Upper Paleolithic, roughly 25,000 years ago. The most likely location was Central Asia, around what is now the Caspian Sea, which only became a sea after the last Ice Age ended and the ice caps over western Russia melted. After the formation of the Caspian Sea, these nomadic hunter-gatherers, ended up on the greener and richer Caucaso-Anatolian side of the Caspian, where they may have domesticated local animals, such as cows, pigs, goats and sheep.

If the mutation for red hair was inherited from Neanderthal, it would have been from a Central Asian Neanderthal, perhaps from modern Uzbekistan, or an East Anatolian/Mesopotamian one. The mutation probably passed on to some other (extinct ?) lineages for a few millennia, before being inherited by the R1b tribe. Otherwise, it could also have arisen independently among R1b people as late as the Neolithic period (but no later).

Red hair and the Indo-European migrations

Developing pottery, or more probably acquiring the skills from Middle Eastern neighbours (notably haplogroup G2a), part of the R1b tribe (and a small minority of G2a3b1) migrated across the Caucasus to take advantage of the vast expanses of grassland for their herds. This is where the Proto-Indo-European culture would have emerged, and spread to the native R1a tribes of the Eurasian steppe, with whom the R1b people blendeded to a moderate level (the reason why there is always a minority of R1b and G2a among predominantly R1a populations today, anywhere from Eastern Europe to Siberia and India).

The domestication of the horse in the Volga-Ural region circa 4000-3500 BCE, combined with the emergence of Bronze Age technology in the North Caucasus around 3300 BCE, would lead to the spectacular expansion of R1b and R1a lineages, an adventure that would lead these Proto-Indo-European speakers to the Atlantic fringe of Europe to the west, to Siberia and North America to the east, and all the way from Egypt to India to the south. From 3500 BCE, the vast majority of the R1b migrated westward along the Black Sea coast, to the metal-rich Balkans, where they mixed with the local inhabitants of Chalcolithic "Old Europe". A small number of R1b accompanied R1a to Siberia and Central Asia, which is why red hair very occasionally turns up in R1a-dominant populations of those areas (who usually still have a minority of R1b among their lineages, although some tribes may have lost them due to the founder effect).

The archeological record indicates that this sustained series of invasions was extremely violent and led to the complete destruction of the until then flourishing civilizations of the Balkans and Carpathians (whose descendants survive as the I2a1b and E1b1b1a lineages). The R1b invaders took local women as wives and concubines, creating a new mixed ethnicity. The language evolved in consequence, adopting loanwords from the languages of Old Europe. This new ethnic and linguistic entity could be referred to as the Proto-Italo-Celto-Germanic people.

After nearly a millennium in the Danubian basin (as far west as Bavaria), they would continue their westward expansion (from 2500 BCE) to Western Europe. In fact, the westward expansion was most likely carried out exclusively by the westernmost faction of R1b, who had settled north of the Alps, around Austria and Bavaria, and developed the Unetice culture. Many R1b lineages stayed behind in the Balkans, where they progressively blended with the natives, then with later immigrants to the region (notably J2, under the Greek, Roman, Byzantine and Ottoman rules) over the next millennia - mostly losing their red hair due to the high incidence of very dark hair in the region today. According to ancient Greek writers, red hair was common among the Thracians, who lived around modern Bulgaria, an region where rufosity has almost completely disappeared today. Red hair alleles may have survived in the local gene pool though, but cannot be expressed due to the lack of other genes for light hair pigmentation.

The red-haired Proto-Italic, Proto-Celtic and Proto-Germanic split in three branches during the progressive expansion of the successive Bronze-age Unetice, Tumulus and Urnfield cultures from Central Europe. The Proto-Germanic branch, originating as the R1b-U106 subclade, is thought to have migrated from present-day Austria to the Low Countries and north-western Germany. They would continue their expansion (probably from 1200 BCE) to Denmark, southern Sweden and southern Norway, where, after blending with the local I1 and R1a people, the ancient Germanic culture emerged.

Nowadays, the frequency of red hair among Germanic people is highest in the Netherlands, Belgium, north-western Germany and Jutland, i.e. where the percentage of R1b is the highest, and presumably the first region to be settled by R1b, before blending with the blond-haired R1a and I1 people from Scandinavia and re-expanding south to Germany during the Iron Age, with a considerably lower percentage of R1b and red-hair alleles. Red-haired is therefore most associated with the continental West Germanic peoples, and least with Scandinavians and Germanic tribes that originated in Sweden, like the Goths and the Vandals. This also explains why the Anglo-Saxon settlements on southern England have a higher frequency of redheads than the Scandinavian settlements of northeast England.

The Italic branch crossed the Alps around 1300 BCE and settled across most of the peninsula, but especially in Central Italy (Umbrians, Latins, Oscans). They probably belonged predominantly to the R1b-U152 subclade. It is likely that the original Italics had just as much red hair as the Celts and Germans, but lost them progressively as they intermarried with their dark-haired neighbours, like the Etruscans. The subsequent Gaulish Celtic settlements in northern Italy increased the rufosity in areas that had priorly been non-Indo-European (Ligurian, Etruscan, Rhaetic) and therefore dark-haired. Nowadays red hair is about as common in northern and in central Italy.

The Celtic branch is the largest and most complex. The area that was Celtic-speaking in Classical times encompassed regions belonging to several distinct subclades of R1b-S116 (the Proto-Italo-Celtic haplogroup). The earliest migration of R1b to Western Europe must have happened with the diffusion of the Bronze Age to France, Belgium, Britain and Ireland around 2100 BCE - a migration best associated with the R1b-L21 subclade. A second migration took place around 1800 BCE to Southwest France and Iberia, and is associated with R1b-Z196. These two branches are usually considered as Celtic, but was probably more distinct than the later continental Celtic were from Italic languages, due to its earlier split. The Northwest Celtic branch could have been ancestral to Goidelic languages (Gaelic), and the south-western one to Celtiberian. Both belong to the Q-Celtic group, as opposed to the P-Celtic group, to which Gaulish and Brythonic belong and which is associated with the expansion of the Hallstatt and La Tne cultures and R1b-U152 (the same subclade as the Italic branch). Nowadays, red hair is found in all three Celtic branches, although it is most common in the R1b-L21 branch. The reason is simply that it is the northernmost branch (red hair being more useful at higher latitudes) and that the Celtic populations of Britain and Ireland have retained the purest Proto-Celtic ancestry (extremely high percentage of R1b).

Red hair was also found among the tartan-wearing Chrchn man, one of the Tarim mummies dating from 1000 BCE, who according to the author were an offshoot of Central European Celts responsible for the presence of R1b among modern Uyghurs. The earlier, non-tartan-wearing Tarim mummies from 2000 BCE, which were DNA tested and identified as members of haplogroup R1a, did not have red hair, just like modern R1a-dominant populations.




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