The Neanderthals
2012 genetic studies seem to suggest that modern humans may have mated with “at least two groups” of archaic humans: Neanderthals and Denisovans. It is suggested that Denisovans shared a common origin with Neanderthals, that they ranged from Siberia to Southeast Asia, and that they lived among and interbred with the ancestors of some modern humans, with about 3% to 5% of the DNA of Melanesians and Aboriginal Australians deriving from Denisovans.
Neanderthals were archaic humans who lived in Eurasia during roughly 250,000 to 40,000 years ago. They seem to have appeared in Europe and expanded into Southwest and Central Asia. Total Neanderthal effective population size has been estimated at close to 15,000 individuals (corresponding to a total population of roughly 150,000 individuals), living in small isolated, inbred groups.
Since 2010, evidence for substantial admixture of Neanderthals DNA in modern populations has accumulated. Evidence of admixture was found in both European and Asian populations, but not in Africans, suggesting that interbreeding between Neanderthals and anatomically modern humans took place after the recent “out of Africa” migration, likely between 60,000 and 40,000 years ago. This is a counter to strict versions of the recent African origin theory, since it would imply that at least part of the genome of Europeans would descend from Neanderthals.
Both Neanderthals and anatomically modern humans are thought to have evolved from Homo erectus between 300,000 and 200,000 years ago. H. erectus had emerged around 1.8 million years ago, and had long been present, in various subspecies throughout Eurasia. The divergence time between the Neanderthal and modern human lineages is estimated at between 800,000 and 400,000 years ago.
Early Neanderthals, living before the Eemian interglacial (130 ka), are poorly known and come mostly from European sites. From 130 ka onwards, the quality of the fossil record increases dramatically. From then on, Neanderthal remains are found in Western, Central, Eastern, and Mediterranean Europe, as well as Southwest, Central, and Northern Asia up to the Altai Mountains in Siberia. No Neanderthal has ever been found outside Central to Western Eurasia, namely neither to the south of 30° N (Shuqba, Levant), nor east of 85° E (Denisova, Siberia).
About 55,000 years ago, the climate began to fluctuate wildly from extreme cold conditions to mild cold and back in a matter of decades. Neanderthal bodies were well-suited for survival in a cold climate—their stocky chests and limbs stored body heat better than the Cro-Magnons. Neanderthals died out in Europe between 41,000 and 39,000 years ago, apparently coinciding with the start of a very cold period.
Raw material sourcing and the examination of faunal remains by Adler et al. (2006) in the southern Caucasus suggest that modern humans may have had a survival advantage during this period, being able to use social networks to acquire resources from a greater area. They found that in both the Late Middle Palaeolithic and Early Upper Palaeolithic more than 95% of stone artifacts were drawn from local material, suggesting Neanderthals restricted themselves to more local sources.
In November 2011 tests conducted at the Oxford Radiocarbon Accelerator Unit in England on what were previously thought to be Neanderthal baby teeth, which had been unearthed in 1964 from the Grotta del Cavallo in Italy, were identified as the oldest modern human remains discovered anywhere in Europe, dating from between 43,000 and 45,000 years ago.
Modern humans co-existed with them in Europe starting around 45,000 years ago and perhaps even earlier. Neanderthals inhabited that continent long before the arrival of modern humans. These modern humans may have introduced a disease that contributed to the extinction of Neanderthals, and that may be added to other recent explanations for their extinction.
When Neanderthal ancestors left Africa roughly 100,000 years earlier they adapted to the pathogens in their European environment, unlike modern humans who adapted to African pathogens. If contact between humans and Neanderthals occurred in Europe and Asia the first contact may have been devastating to the Neanderthal population, because they would have had little if any immunity to the African pathogens.
More recent historical events in Eurasia and the Americas show a similar pattern, where the unintentional introduction of viral or bacterial pathogens to unprepared populations has led to mass mortality and local population extinction. The most well-known example of this is the arrival of Christopher Columbus to the New World, which brought and introduced foreign diseases when he and his crew arrived to a native population who had no immunity.
The redheads and blond hair
A 2007 genetic study suggested some Neanderthals may have had red hair and blond hair, along with a light skin tone. As of 2015, the earliest light eyes and light hair of hominid (Homo sapiens) individuals after the long extinct Neanderthals have been documented in 8,000-year-old remains in Motala, Sweden, belonging to subclades of Haplogroup I2 and mitochondrial Haplogroup U5.
The lightness of the hair ultimately depends on other mutations regulating the general pigmentation of both the skin and hair. 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).
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.
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.
However, 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. All these people share a common ancestry that can be traced back to a single Y-chromosomal haplogroup: R1b.
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).
However, 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 lineages 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.
Anatomically Modern Humans (AMH)
Haplogroup IJK is a human Y-chromosome DNA haplogroup. IJK is a primary branch of the macrohaplogroup HIJK. Its direct descendants are haplogroup IJ and haplogroup K.
The basal paragroup HIJK* has not been identified in living males or ancient remains. Populations with high proportions of males who belong to descendant major haplogroups of Haplogroup HIJK live across widely dispersed areas and populations.
The existence of Haplogroup IJK – the ancestor of both haplogroups IJ and K (M9) – and its evolutionary distance from other subclades of Haplogroup F (M89), supports the inference that haplogroups IJ and K both arose in Southwestern Asia. Living carriers of F* and IJ* have been reported from the Iranian Plateau.
Around 40,000 years ago haplogroup IJK seperated into two distinct new haplogroups which were japplogroups IJ and K. Both originated in southwest Asia but most of the K people went up into central Asia where new mutations took place within the haplogroup. Confirmed examples of K-M9* now appear to be most common amongst some populations in Island South East Asia and Melanesia.
Haplogroup K or K-M9 represents a geographically widespread and diverse haplogroup. The lineages have long been found among males on every continent. It is an old lineage that arose approximately 47,000-50,000 years ago, probably in South Asia or West Asia.
Relative to its age, the internal structure of K2 is extremely complex, and subclades of it are carried by males native to regions including Australasia, Oceania, Southeast Asia, South Asia, East Asia, Central Asia, the Americas, Europe, and the Horn of Africa.
It seems that a rapid diversification of K2 (K-M526) into K2a and K2b, followed by K2b1 and P (also known as K2b2) likely occurred in Southeast Asia. K2a and C1 have been found in the oldest sequenced male remains from Western Eurasia (dating from circa 45,000 to 35,000 years BP), such as: Ust’-Ishim man (modern west Siberia) K2a*, Oase 1 (Romania) K2a*, Kostenki 14 (south west Russia) C1b, and Goyet Q116-1 (Belgium) C1a.
This was followed by the relatively rapid westward expansion of P1 (P-M45), the immediate ancestor of both Haplogroups Q and R, which likely emerged in Southeast Asia. It seems that a rapid diversification process of K-M526 likely occurred in Southeast Asia, with subsequent westward expansions of the ancestors of haplogroups R and Q.
Haplogroup Q (M242) is the predominant Y-DNA haplogroup among Native Americans and several peoples of Central Asia and Northern Siberia. Q-M242 is believed to have arisen around the Altai Mountains area (or South Central Siberia), approximately 17,000 to 31,700 years ago.
The SNP M207, which defines Haplogroup R, is believed to have arisen during the Upper Paleolithic era, about 27,000 years ago. Only one confirmed example of basal R* has been found, in 24,000 year old remains, known as MA1, found at Mal’ta–Buret’ culture near Lake Baikal in Siberia.
Haplogroup I and J were subsequently distributed in Asia and Europe in a disjunctive phylogeographic pattern typical of “sibling” haplogroups. A natural geographical corridor like the Balkans is likely to have been used later by members of other subclades of IJ, as well as other haplogroups, including those associated with Early European Farmers.
Haplogroup IJ was in the Middle East and/or Europe about 40,000 years ago. Early evidence for haplogroup J has been found in the Caucasus and Iran. In addition, living examples of the precursor Haplogroup IJ* have been found only in Iran, among the Mazandarani and ethnic Persians from Fars. This may indicate that IJ originated in South West Asia.
Haplogroup I (M170) diverged from common ancestor IJ* about 43,000 years BP. The TMRCA (time to most recent common ancestor) for I-M170 was estimated in 2008 to be 22,200 years ago, with a confidence interval between 15,300–30,000 years ago. The oldest I-M170 found is that of an individual known as Krems WA3 (lower Austria), dating from circa 33,000-24,000 BP.
This would make the founding event of I-M170 approximately contemporaneous with the Last Glacial Maximum (LGM), which lasted from 26,500 years ago until approximately 19,500 years ago.
It would seem to be that separate waves of population movement impacted Southeastern Europe. The role of the Balkans as a long-standing corridor to Europe from Anatolia and/or the Caucasus is shown by the common phylogenetic origins of both haplogroups I and J in the parent haplogroup IJ (M429). This common ancestry suggests that the subclades of IJ entered the Balkans from Anatolia or the Caucasus, some time before the Last Glacial Maximum.
The available evidence suggests that I-M170 was preceded into areas in which it would later become dominant by haplogroups K2a (K-M2308) and C1 (Haplogroup C-F3393). Consequently, I-M170 represents up to one-fifth of the male population of Europe, being the continent’s second major Y-DNA haplogroup (behind Haplogroup R).
I-M170 is one of the most numerous haplogroups among European males. Subclades can be found in most present-day European populations, with peaks in some Northern European and South East European countries. The haplogroup reaches its maximum frequency in the Balkans (with the highest concentration in present-day Herzegovina). It may be associated with unusually tall males, since those in the Dinaric Alps have been reported to be the tallest in the world.
It is speculated that the initial dispersion of this population corresponds to the diffusion of the Gravettian culture. Later the haplogroup, along with two cases of Haplogroup C, was found in human remains belonging to the culture and in individuals of the Magdalenian and Azilian cultures.
It is suggested that each of the ancestral populations now dominated by a particular subclade of Haplogroup I-M170 experienced an independent population expansion immediately after the Last Glacial Maximum.
Haplogroup I2 (I-M438) originated some time around 26,000–31,000 BCE and has two primary subclades: I-L460 and I-L1251. The haplogroup reaches its maximum frequency in the Dinaric Alps in Eastern Europe (especially in the Balkans), where the men are on record as being the tallest in the world, with a male average height of 185.6 cm (6 ft 1.1 in).
Haplogroup I2a may be the haplogroup of the first anatomically modern humans to inhabit Europe, Cro-Magnon. Basal I2* (I-M438*) has been found in ancient remains from Frankthi cave, in the eastern Peloponnese region of Greece. Along with its modern presence in Crete and Sicily, this may suggest that the haplogroup originated in the Eastern Mediterranean. Haplogroup I2a was the most frequent Y-DNA among western European mesolithic hunter gatherers (WHG).
An I2a1 carrier was a carrier of red hair and others of genes of blond/light hair, while all the Motala hunter-gatherers were light-skinned and blue-eyed males. (Light-skin genes, but not those for blond/red hair, have been found in Siberia on a 17,000-year-old carrier of Haplogroup R*, as well as 8,000–9,000-year-old R1a remains from Karelia.)
Due to the arrival of so-called Early European Farmers, I-M170 is outnumbered by Haplogroup G among Neolithic European remains and by Haplogroup R in later remains. I2 subclade of I-M170 is the main haplogroup found on male remains in Mesolithic Europe, until circa 6,000 BCE, when mass migration into Europe of Middle Eastern farmers carrying Y-DNA G2a happened.
Haplogroup R1b
Haplogroup R* originated in North Asia just before the Last Glacial Maximum (26,500-19,000 years ago). This haplogroup has been identified in the remains of a 24,000 year-old boy from the Altai region, in south-central Siberia (Raghavan et al. 2013). This individual belonged to a tribe of mammoth hunters that may have roamed across Siberia and parts of Europe during the Paleolithic.
Autosomally this Paleolithic population appears to have contributed mostly to the ancestry of modern Europeans and South Asians, the two regions where haplogroup R also happens to be the most common nowadays (R1b in Western Europe, R1a in Eastern Europe, Central and South Asia, and R2 in South Asia).
The oldest forms of R1b (M343, P25, L389) are found dispersed at very low frequencies from Western Europe to India, a vast region where could have roamed the nomadic R1b hunter-gatherers during the Ice Age.
The three main branches of R1b1 (R1b1a, R1b1b, R1b1c) all seem to have stemmed from the Middle East. The southern branch, R1b1c (V88), is found mostly in the Levant and Africa. The northern branch, R1b1a (P297), seems to have originated around the Caucasus, eastern Anatolia or northern Mesopotamia, then to have crossed over the Caucasus, from where they would have invaded Europe and Central Asia. R1b1b (M335) has only been found in Anatolia.
Like its northern counterpart (R1b-M269), R1b-V88 is associated with the domestication of cattle in northern Mesopotamia. Both branches of R1b probably split soon after cattle were domesticated, approximately 10,500 years ago (8,500 BCE).
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.
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.
It has been hypothetised that R1b people (perhaps alongside neighbouring J2 tribes) were the first to domesticate cattle in northern Mesopotamia some 10,500 years ago. R1b tribes descended from mammoth hunters, and when mammoths went extinct, they started hunting other large game such as bisons and aurochs. With the increase of the human population in the Fertile Crescent from the beginning of the Neolithic (starting 12,000 years ago), selective hunting and culling of herds started replacing indiscriminate killing of wild animals.
The increased involvement of humans in the life of aurochs, wild boars and goats led to their progressive taming. Cattle herders probably maintained a nomadic or semi-nomadic existence, while other people in the Fertile Crescent (presumably represented by haplogroups E1b1b, G and T) settled down to cultivate the land or keep smaller domesticates.
The analysis of bovine DNA has revealed that all the taurine cattle (Bos taurus) alive today descend from a population of only 80 aurochs. The earliest evidence of cattle domestication dates from circa 8,500 BCE in the Pre-Pottery Neolithic cultures in the Taurus Mountains.
The two oldest archaeological sites showing signs of cattle domestication are the villages of Çayönü Tepesi in southeastern Turkey and Dja’de el-Mughara in northern Iraq, two sites only 250 km away from each others. This is presumably the area from which R1b lineages started expanding – or in other words the “original homeland” of R1b.
The early R1b cattle herders would have split in at least three groups. One branch (M335) remained in Anatolia, but judging from its extreme rarity today wasn’t very successful, perhaps due to the heavy competition with other Neolithic populations in Anatolia, or to the scarcity of pastures in this mountainous environment. A second branch migrated south to the Levant, where it became the V88 branch. Some of them searched for new lands south in Africa, first in Egypt, then colonising most of northern Africa, from the Mediterranean coast to the Sahel.
The third branch (P297), crossed the Caucasus into the vast Pontic-Caspian Steppe, which provided ideal grazing grounds for cattle. They split into two factions: R1b1a1 (M73), which went east along the Caspian Sea to Central Asia, and R1b1a2 (M269), which at first remained in the North Caucasus and the Pontic Steppe between the Dnieper and the Volga.
It is not yet clear whether M73 actually migrated across the Caucasus and reached Central Asia via Kazakhstan, or if it went south through Iran and Turkmenistan. In any case, M73 would be a pre-Indo-European branch of R1b, just like V88 and M335.
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).
Proto-Indo-Europeans
Developing pottery, or more probably acquiring the skills from Middle Eastern neighbours (notably tribes belonging to haplogroup G2a), part of the R1b tribe 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 blended to a moderate level (the reason why there is always a minority of R1b 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 working 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 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. 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 have remained in the Balkans, where they have gradually mixed with the indigenous populations, then with successive waves of immigrants and invaders over the next millennia, such as the Greeks, the Romans, the Bulgars and the Ottomans.
Almost all trace of red hair was lost in south-eastern Europe due to the high number of dark haired people brought by the long wave of invasions to the region over the last 5000 years. 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-Indo-Europeans split in three branches (Proto-Italic, Proto-Celtic and Proto-Germanic ) 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-DF27.
These two branches are usually considered Celtic, but because of their early separation, they are likely to be more different from each other than were the later Italic and continental Celtic branches (both R1b-U152).
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 Tène cultures and R1b-U152 (the same subclade as the Italic branch).
The 45th parallel north
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 Chärchän 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.
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.
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 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. 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.
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 expansion of agriculture from the Near East followed two separate routes.
Even as far back as Neolithic times, the 45th parallel roughly divided the Mediterranean Cardium Pottery culture from the Central European Linear Pottery culture. The southern route followed the Mediterranean coastlines until Iberia, while the northern route diffused along the Danubian basin then the North European Plain until the Low Countries and the Baltic.
Each group of farmer blended with indigenous Mesolitic hunter-gatherers over time, but those i the Mediterranean may have been genetically distinct from those of central and northern Europe. Then, from the Bronze Age, the Indo-European migrations from the Pontic Steppe affected much more central and northern Europe, considerably altering the gene pool and local lifestyle, by bringing East European and Caucasian genes and dairy farming, in addition to Indo-European language and culture.
It is only in the Late Bronze Age (c. 1500–1155 BCE), over a thousand years after the Indo-European expansion into Central Europe, that the Proto-Celts really expanded over the Italian and Iberian peninsulas. Greece also didn’t become Indo-Europeanised until the Mycenaeans, another group of Indo-European speakers from the Steppe took over the country circa 1600 BCE.
Slavic, Baltic and Finnish people are predominantly descended from peoples belonging to haplogroups 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.
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.