Genetic history of Europe

The genetic history of Europe can be inferred by observing the patterns of genetic diversity across the continent and comparing them with the patterns on the adjacent land masses. These patterns can be found by using classical genetic markers or by using molecular genetics (autosomal, Y-chromosome and mitochondrial DNA). Most data is from modern populations, but there is a small amount of information from ancient DNA. European populations have a complicated demographic and genetic history, including many layers of successive migrations between different time periods, from the first appearance of Homo sapiens in the Upper Paleolithic to contemporary immigration.

The diversion of Haplogroup F and its descendants.

Relation of Neanderthals and modern humans

Before modern humans arrived in Europe some 45,000 years ago, the continent was inhabited by Neanderthals, who did not die out until about 25,000 years ago. There continues to be much speculation as to whether the two genetic groups interbred. Analysis of the DNA distributions of the two groups shows significant difference, so any such offspring were unlikely to be fertile.

Relation of present population to other populations

Classical genetics studies

Percentage genetic distances among major continents based on 120 classical polymorphisms

	Africa	Oceania	East Asia	Europe
Oceania	24.7
East Asia	20.6	10
Europe	16.6	13.5	9.7
America	22.6	14.6	8.9	9.5

In the 1990s, a study by Luigi Luca Cavalli-Sforza of the Stanford University School of Medicine, using 120 blood polymorphisms, provided information on genetic relatedness of the various continental populations. Genetic distance is a measure of genetic difference between two populations. It is based on the principle that two populations that share similar frequencies of a trait are more closely related than populations that have more divergent frequencies of the trait. In its simplest form, it is the difference in frequencies of a particular trait between two populations. For example, the frequency of RH negative individuals is 50.4% among Basques, 41.2% in France and 41.1% in England. Thus regarding the RH negative trait, the genetic difference between the Basques and French is 9.2% and the genetic difference between the French and the English is 0.1%. Averaged over several traits this approach can give a measure of the overall genetic relatedness of various populations.

According to the study, all non-African populations are more closely related to each other than to Africans; this supports the hypothesis that all non-Africans descend from a single African population. The genetic distance from Africa to Europe (16.6) is shorter than the genetic distance from Africa to East Asia (20.6), and much shorter than that from Africa to Australia (24.7). The simplest explanation for this short genetic distance, according to Cavalli-Sforza, is that substantial gene exchange has taken place between Africa and its neighbouring continents, after the major "Out of Africa" emigration which was ancestral to Australian aboriginals. Cavalli-Sforza suggested that this admixture took place 30,000 years ago. The overall contributions from Asia and Africa to the modern population were estimated to be around two-thirds and one-third, respectively. Europe's genetic variation is about a third of that of other continents. The timing and number of important human migrations out of Africa remain a major point of discussion today.

According to Guglielmino et al. (1990),

Principal coordinate analysis shows that Lapps/Sami are almost exactly intermediate between people located geographically near the Ural mountains and speaking Uralic languages, and central and northern Europeans. Hungarians and Finns are definitely closer to Europeans. An analysis of genetic admixture between Uralic and European ancestors shows that Lapps/Sami are slightly more than 50% European, Hungarians are 87% European, and Finns are 90% European. There is basic agreement between these conclusions and historical data on Hungary. Less is known about Finns and very little about Lapps/Sami.

DNA studies

Studies of the genetic history of Europe have been done using mitochondrial DNA (mtDNA), Y chromosome DNA and autosomal DNA. The first allows to trace female lines, the second allows to trace male lines, while the third provides many possible markers (over 500,0000 have been used) but allows descents only to be determined on a statistical basis because of recombination of male/female DNA. By comparing the polymorphisms found in DNA analyses, haplogroup trees have been defined. These have made use of both single nucleotide polymorphisms and short tandem repeats, which produce information about long and short timescale changes respectively.

Worldwide DNA studies have shown that a group of Homo sapiens left Africa for the Yemen some 50,000-80,000 years ago. Some of their descendants started entering Europe about 40,000 years ago. The Y-chromosome and the mtDNA haplogroups found in Europe differ in their frequency distributions from those in Africa, Asia and the Middle East. However some predominantly European haplogroups are found in Asia and vice versa. A similar correspondence is found between Africa and Europe.

This relationship of European to Asian populations has been shown for example by the spread of the Y-chromosome marker Haplogroup N, in Northern Europe. [1]. Several studies strongly suggest a pattern of migrations from Asia to Northern Europe over the last 4000 years. For example, the studies by Zerjal et al. 1997, Su et al. 1999, and Lell et al. 2002 established a significant presence of this Asian marker in different European peoples, ranging from a 52% in Finns, 47% in Lithuanians, 37% in Estonians and 32% in Latvians to 14% in Russians, 11% in Ukranians, 8% in North Swedes, 6% in Gotlanders, 6% in Norwegians, 4% in Poles, 3% in Germans and 1% in Turks, among others.

European population structure

In 2006, an autosomal analysis comparing samples from various European populations concluded that “there is a consistent and reproducible distinction between ‘northern’ and ‘southern’ European population groups”. Most individual participants with southern European ancestry (Italian, Greek, Armenian, Portuguese, and Spanish) have >85% membership in the ‘southern’ population; and most northern, western, eastern, and central Europeans have >90% in the ‘northern’ population group. Ashkenazi Jewish as well as Sephardic Jewish origin also showed >85% membership in the ‘southern’ population, consistent with a later Mediterranean origin of these ethnic groups". [2] Many of the participants in this study were actually American citizens who self identified with different European ethnicities and were not Europeans.

Somewhat contradicting these findings, a similar study in 2007 using samples exclusively from Europe found that the most important genetic differentiation in Europe occurs on a line from the north to the south-east (northern Europe to the Balkans), with another east-west axis of differentiation across Europe. Its findings were consistent with earlier results based on mtDNA and Y-chromosonal DNA that support the theory that modern Iberians (Spanish and Portuguese) hold the most ancient European genetic ancestry, as well as separating Basques and Sami from other European populations. It suggested that the English and Irish cluster with other Northern and Eastern Europeans such as Germans and Poles, while some Basque and Italian individuals also clustered with Northern Europeans. Despite these stratifications, it noted the unusually high degree of European homogeneity: "there is low apparent diversity in Europe with the entire continent-wide samples only marginally more dispersed than single population samples elsewhere in the world."

In fact, according to another European wide study, the main components in the European genomes appear to derive from ancestors whose features were similar to those of modern Basques and Near Easterners, with average values greater than 35% for both these parental populations, regardless of whether or not molecular information is taken into account. The lowest degree of both Basque and Near Eastern admixture is found in Finland, whereas the highest values are, respectively, 70% ("Basque") in Spain and more than 60% ("Near Eastern") in the Balkans.

In 2008, two international research teams published analyses of large-scale genotyping of large samples of Europeans, revealing relatively little genetic differentiation between the various European populations sampled. (The samples for these papers used overlapped somewhat, though the papers were not collaborative.) But the number of loci included in the analysis was sufficient to detect the geographic region an individual comes from to within about 840 km (for 90% of individuals), as long as the individual's recent ancestry is from that region (for example if an individual has parents from different regions of Europe, then that individual will be placed on the map exactly equidistant between the parent's populations of origin, and not near either parental population). Southern Europeans have more genetic diversity, having both less linkage disequilibrium and greater heterozygosity, indicating a larger effective population size and/or population expansion from southern to northern Europe, as expected. Populations did not form clusters as previous studies have found (see Seldin et al. 2006 and Bauchett et al. 2007), but showed a correlation between genetic distance and geographic distance. The researchers take this observation to imply that, genetically speaking, Europeans are not distributed into discrete, populations.

A very recent study in May 2009 that studied 19 populations from Europe using 270,000 SNPs highlighted the genetic diversity or European populations corresponding to the northwest to southeast gradient and distinguished "four several distinct regions" within Europe:

• Finland
• the Baltic region (Estonia, Latvia and Lithuania), Eastern Russia and Poland
• Central and Western Europe
• Italy, "with the southern Italians being more distant"

In this study, Fst (Fixation index) was found to correlate considerably with geographic distances ranging from ≤0.0010 for neighbouring populations to 0.0200-0.0230 for Southern Italy and Finland. For comparisons, pair-wise Fst of non-european samples were as follows: Europeans – Africans (Yoruba) 0.1530; Europeans – Chinese 0.1100; Africans (Yoruba) – Chinese 0.1900 .

Haplogroups in Europe

Human Y-chromosome DNA haplogroups

Distribution of R1a (purple) and R1b (red). Two of the three most common Human Y-chromosome DNA haplogroups in Europe. Black represents all the other haplogroups.

There are three major Y-chromosome DNA haplogroups which largely account for most of Europe's present-day population.

• Haplogroup R1b is common on the western Atlantic coast of Europe, from the Iberian Peninsula (comprising Spain and Portugal) to Ireland, Wales, England and Scotland, and Jutland.
• Haplogroup I is common across Germany, the Netherlands, Austria, and up into Scandinavia, as well as a very high amount in the western Balkans.
• Haplogroup R1a is common in Central and Eastern Europe (and is also common in Central Asia and the Indian subcontinent).

Most common of all haplogroups among western Europeans is R1b. The following values of Hg R1b are: Welsh: 89.0%; Basques: 88.1%; Irish: 81.5%; Scots: 77.1%; British: 68.8; Non-Basque Spaniards: 68.0 (Catalans: 79.2; Andalusians: 65.5); Belgians: 63.0; Portuguese (North): 62.0%; Italians (North-central): 62.0; English (Central): 61.9%; Portuguese (South): 56.0%; French: 52.2%; Danes: 41.7%, Germans: 47.9; Czechs & Slovaks: 35.6%; Italians (Calabria): 32.4; Norwegians: 25.9; Greeks: 22.8%; Italians (Sardinia): 22.1%; Slovenians: 21%; Swedes: 20.0; Romanians: 18.0%; Albanians: 17.6%; Bulgarians: 17.0%; Polish: 16.4%; Turks: 16.3%; Croatians (mainland): 15.7%; Hungarians: 13.3%; Serbs: 10.6%; Cypriots: 9.0%.

Among European populations, diversity is highest in Eastern Europe, despite lower frequencies. Diversity analysis indicates that all European variants of R1b shared an existence in Central Asia (Kazakhstan) before migrating to Russia and then splitting into two major migrations, moving primarily along rivers and coastlines.

Each haplogroup clade has subclades. R1a and R1b are subclades of Haplogroup R (Y-DNA) Two main subgroups of Haplogroup I (Y-DNA) are I-M253/I-M307/I-P30/I-P40, which according to the International Society of Genetic Genealogy "has highest frequency in Scandinavia, Iceland, and northwest Europe" and I-S31, which according to the International Society of Genetic Genealogy, "includes I-P37.2, which is the most common form in the Balkans and Sardinia, and I-S23/I-S30/I-S32/I-S33, which reaches its highest frequency along the northwest coast of continental Europe."

The extent of the population changes resulting from the introduction of Neolithic technology into Europe are still debated. There is evidence both for and against a dominating affect from "demic diffusion" from the Near East: G Barbujani and L Chikhi (2006) state,

Genetic studies have failed to settle the controversy so far, because they have been interpreted in different ways... A rather heated debate followed, and is still continuing."

Also, around 4,500 years ago, Haplogroup N3 began moving westward from west of the Ural mountains, and seems to follow closely the spread of the Finno-Ugric languages. It is also present at high frequencies in northern Russians, reflecting the absorption of Finno-Ugric tribes.

Human mitochondrial DNA haplogroups

There have been a number of studies about the mitochondrial DNA haplogroups (mtDNA) in Europe. According to the University of Oulu Library in Finland:

Classical polymorphic markers (i.e. blood groups, protein electromorphs and HLA antigenes) have suggested that Europe is a genetically homogeneous continent with a few outliers such as the Saami, Sardinians, Icelanders and Basques (Cavalli-Sforza et al. 1993, Piazza 1993). The analysis of mtDNA sequences has also shown a high degree of homogeneity among European populations, and the genetic distances have been found to be much smaller than between populations on other continents, especially Africa (Comas et al. 1997).

The mtDNA haplogroups of Europeans are surveyed by using a combination of data from RFLP analysis of the coding region and sequencing of the hypervariable segment I. About 99% of European mtDNAs fall into one of ten haplogroups: H, I, J, K, M, T, U, V, W or X (Torroni et al. 1996a). Each of these is defined by certain relatively ancient and stable polymorphic sites located in the coding region (Torroni et al. 1996a)... Haplogroup H, which is defined by the absence of a AluI site at bp 7025, is the most prevalent, comprising half of all Europeans (Torroni et al. 1996a, Richards et al. 1998)... Six of the European haplogroups (H, I, J, K, T and W) are essentially confined to European populations (Torroni et al. 1994, 1996a), and probably originated after the ancestral Caucasoids became genetically separated from the ancestors of the modern Africans and Asians.

Apparent Migrations into Europe

The prehistory of the European peoples can be traced by the examination of archaeological sites, linguistic studies, and by the examination of the DNA of the people who live in Europe now, or from recovered ancient DNA. Much of this research is ongoing, and discoveries are still being continually made, so theories rise and fall. Although it is possible to track the various migrations of people across Europe using founder analysis of DNA, most information on these movements comes from archeology.

Five patterns of genetic relatedness have been identified since the early "principle components" studies of Cavalli-Sforza:

1. A cline of genes with highest frequencies in the Middle East, spreading to lowest levels northwest.
2. A cline of genes with highest frequencies amongst Finnish and Saami in the extreme north east, and spreading to lowest frequencies in the south west.
3. A cline of genes with highest frequencies in the area of the lower Don and Volga rivers in southern Russia, and spreading to lowest frequencies in Iberia, Southern Italy, Greece and the areas inhabited Saami speakers in the extreme north of Scandinavia.
4. A cline of genes with highest frequencies in the Balkans and Southern Italy, spreading to lowest levels in Britain and the Basque country.
5. A cline of genes with highest frequencies in the Basque country, and lower levels beyond the area of Iberia and Southern France.

The exact causes of each of these is the subject of continuing discussion concerning geographical routes within Europe, as well as different periods of time. This article shall summarize current thinking about migrations in different periods, and then consider some of the main geographical sources of genetic diversity in Europe.

Migrations before the Last Glacial Maximum

Further information: Paleolithic Europe

Europe 20,000 years ago, showing coastline, extent of Ice caps and regions where refugia are thought to have been situated.

Modern humans (Cro Magnon) began to colonize Europe in the Paleolithic about 40,000 years ago, as evidenced by the spread of the Aurignacian culture. Modern humans may have arrived along two major routes either side of the Black Sea. By about 25,000 years ago, the prior inhabitants (our cousin species H. neanderthalensis) were either killed off or absorbed into the population and ultimately became extinct. Martin Richards et al. found that 21% of extant studied the mtDNA lines of Europe came from pre-glacial migrations. The two main haplogroups were U and HV, which arrived around 50,000 and 35,000 years ago respectively. Early on, HV split into Pre-V (around 26,000 years old) and the larger branch H, both of which spread over all Europe. Haplogroup H accounts for about half the gene lines in Europe, with many subgroups. The large Y-chromosome haplogroup R1 moved into Central Europe from the east 30,000 years ago and to the south-west before the LGM.

Last Glacial Maximum: Refugia

Further information: Last Glacial Maximum

About 25,000 years ago began the last very cold period (the Last Glacial Maximum, LGM), rendering much of Europe uninhabitable. Humans may only have occupied certain regions of Europe at this time. These areas are often called refuges (or refugia) and were located along the northern Mediterranean and Black Sea coasts, as well as in the Balkans and Ukraine. As the glaciers receded from about 16,000 years ago, the populations that had occupied the refuges are thought to have begun to spread and colonise northern Europe. Pre-V's daughter group V (from about 16,300 years ago) gave the first indication of spread from the Galacian refuge, being found mostly in western and northern regions. It is found with highest frequency in Scandinavia and Lapland, but also in south-west France and with declining frequency up the Atlantic coast. Subgroups of haplogroup H seem to have originated in the Iberian refuge and spread, for example, into the British Isles. Presumably as a result of genetic drift, only one Y-chromosome subgroup (R1b) emerged from the Iberian refuge and colonised western Europe. Its frequency of occurrence declines from 90% in Basques to 50% in Germans and 0% around the eastern Baltic coast. In the north-west R1b is partly replaced by R1a, coming from an eastern refuge. There is also an exclusively European haplogroup I, deriving from the Balkans but with high frequencies in Scandinavia and northern Germany. Martin Richards estimates that overall around 50% of mtDNA arrived in the Late Upper Paleolithic, while only around 20% of Y-chromosomes did.

It is thought that there were refugia in the Balkans and the Ukraine that acted as source areas for the repopulation of Europe after the LGM. Associated with these areas are Y-chromosomes I and R1a respectively. People from these refuges reached north-west Europe, while R1a also spread into central Asia and as far as Pakistan and India. There was a major incursion of Haplogroup N into north-eastern Europe. South-eastern Europe shows the incursion of several haplogroups mainly found in the Middle East.

After the LGM

Further information: Mesolithic Europe

File:Early Holocene.png

Possible Post-Glacial population expansions

After a less severe cold event around 12000-10000 years ago, there was an increasing use of microliths and reliance on the coast and sea. Styles of tool making varied by location, suggesting that the population of Europe was settling down. Northern Europe was first settled in the Mesolithic. Martin Richards showed that about 11% of modern mtDNA arrived from the Middle East during the Mesolithic. These types include T, T2 and K which show a significant decline from SE to NW Europe. However Stephen Oppenheimer says that there was further gene flow from Iberia to NW Europe. He has identified four mtDNA subgroups that expanded into western Europe and nine Y-chromosome R1b descendant clusters that expanded in the Mesolithic. In northern Europe there was also mtDNA input from Asia, while the male gene flow was largely from SE Europe and Asia, including descendants of haplogroups R1a and N3, though there was also R1b input.

Holocene migrations

Further information: Neolithic Europe, Neolithic Revolution, and Holocene

Entry via the Balkans from the Near East

The early Holocene saw the continuation of Mesolithic technology in many parts of Europe, and an apparent decrease of population in some parts of southern Europe to very low levels.

Neolithic farming technology entered Europe during the Holocene, first in Greece, and is considered to have made important changes to Europe's genetic make-up. The duration of the Neolithic varied from place to place, starting with the introduction of farming and ending with the introduction of bronze implements. In SE Europe it was approximately 7000-3000 BC while in NW Europe 4500-1700 BC. Besides the introduction of new plants and animals, the Neolithic also saw the beginning of the use of pottery. Pottery remains allow the tracing of the movement of ideas and possibly people across Europe.

Martin Richards estimated that 11% of European mtDNA is due to immigration in this period. Gene flow from SE to NW Europe seems to have continued in the Neolithic, the percentage significantly declining towards the British Isles. Classical genetics also suggested that the largest admixture to the European Paleolithic/Mesolithic stock was due to the Neolithic revolution of the 7th to 5th millennia BC. Three main mtDNA gene groups have been identified as contributing Neolithic entrants into Europe: J, T1 and U3 (in that order of importance). With others they amount up to around 20% of the gene pool.

E1b1b1a2 (also known as E-V13) is the most common subclade of E1b1b throughout most of Europe. It is commonly thought to have been a marker of Neolithic migrations, coinciding with the introduction of Agriculture into Europe, from Anatolia or Levant into the Balkans and Southern Italy, where it has its highest frequency. However, Battaglia et al. (2008) suggest that it actually arrived into the Balkans from Western Asia during the early Holocene, ahead of the Neolithic.

E-V13 is a sub-clade of E1b1b (formerly known as E3b, and also known as E-M215, and equivalent to E-M35) which is thought to have originated in the Horn of Africa. It is by far the most common Y DNA clade in North and Northeast Africa, and is also common throughout the majority of Europe, particularly in the Mediterranean and South Eastern Europe.

The distribution of the V-13 sub-lineage of haplogroup E1b1b in Europe

From the above it can be seen that within a few millennia E1b1b lineages traced a path from an African origin via the Middle East, to Europe where they apparently were present during the incipient Neolithic. Underhill and Kivisild (2007) have remarked that E1b1b seems to represent a late-Pleistocene migration from Africa to Europe over the Sinai Peninsula in Egypt, evidence for which does not show up in mitochondrial DNA.

Bronze and Iron Age migrations

Further information: Bronze Age Europe and Iron Age Europe

The Bronze Age saw the development of long-distance trading networks, particularly along the Atlantic Coast and in the Danube valley. There was migration from Norway to Orkney and Shetland in this period (and to a lesser extent to mainland Scotland and Ireland). There was also migration from Germany to eastern England. Martin Richards estimated that there was about 4% mtDNA immigration to Europe in the Bronze Age. Oppenheimer could find no genetic evidence for any Iron Age migration to Britain.

One theory about the origin of the Indo-European language centres around a hypothetical Proto-Indo-European people, who are traced, in the Kurgan hypothesis, to somewhere north of the Black Sea at about 4500 BCE. They domesticated the horse, and are considered to have spread their culture and genes across Europe. It has been difficult to identify what these "Kurgan" genes might be, though the Y haplogroup R1a is a proposed marker which would indicate that the physical expansion halted in Germany and only the Kurgan culture and language went further. Another hypothesis — the Anatolian hypothesis — suggests an origin in Anatolia with a later expansion from eastern Europe.

To what extent Indo-European migrations replaced the indigenous Mesolithic peoples is debated, but a consensus has been reached that technology and language transfer played a more important role in this process than actual gene-flow.

During the Iron Age, Celts are recorded as having moved from Gaul into northern Italy, Eastern Europe and Anatolia. The relationship between the Celts of Gaul and Spain is unclear as any migration occurred before records exist.

Roman Period admixture

During the period of the Roman Empire, historical sources show that there were many movements of people around Europe, both within and outside the Empire. These included army personnel and administrators as well as private citizens. However, compared with the total population, these movements seem mostly to have been small. No genetic information on these migrations appears to exist other than a person with a rare Yorkshire surname of African ancestry (Y Hg A1).

Sources of genetic admixture in Europe by region

Uralic, Central, and East Asian admixture

Central Asian Y Chromosomes are somewhat common in European populations. Tat-C (haplogroup 16) is a Y-chromosome lineage that originated in Central Asia and likely spread to Northeastern Europe with male Uralic hunter/gatherer migrations occurring over the last 4000 years. . Today it's found In Northern and Northeast Europe in low to high frequencies. It is found in Finland (55%), European Russia (14%), Ukraine (11%), Lithuania (47%), Estonia (37)%, Sweden (8%), Norway, (6%), Poland (4%), Germany (3%), Slovakia (3%), Denmark (2%), and Belarus (2%).

Gene flow from Africa

File:Haplogroup E.png

The spread of Haplogroup E from Africa into Europe according to Semino et al 2004

In the period since the major OOA migrations and recent centuries, the clearest sign of gene flow from Africa to Europe is the Y-DNA haplogroup E1b1b (also known as E-M35 or E-M215), which mostly likely entered Europe in in the Holocene. Underhill and Kivisild (2007) have remarked that E1b1b seems to represent a late-Pleistocene migration from Africa to Europe over the Sinai Peninsula in Egypt.

At least 7.2% of European Males carry the African Haplogroup. It is the third most frequent haplotype in Europe, and has its highest concentration is found in the Balkans where its frequency is about 50%. E1b1b is a subclade of Haplogroup E, the most common haplogroup in Africa. E1b1b is a sibling of E1b1a, which is the signature haplogroup of the Bantu migration. The origins of E1b1b are thought to lie in the region of the Horn of Africa but the main clades present in Europe are:

• E-M78 thought to originate in the region near the border of what is now Egypt and Sudan. This clade is most common in Europe in the Balkans and Southern Italy, with the exception of its sub-clade E-V65, associated with the Maghreb, which is most common in Southern Italy and Iberia. E-M78 is dominated in Europe by its sub-clade E-V13, which is associated with late Mesolithic or early Neolithic immigration from the Levant, and in either case with the early spread of farming technology into Europe.
• E-M81 which is strongly associated with the Maghreb region of Northern Africa. Like E-V65, this clade is most common in Europe within parts of Southern Italy and Iberia.

The Mediterranean Sea and the Sahara Desert were formidable barriers to gene flow between Sub-Saharan Africa and Europe. But Europe was periodically accessible by Africans due to fluctuations in the size and climate of the Sahara. At the Strait of Gibraltar, Africa and Europe are separated by only 15km of Ocean. At the Suez, Eurasia is connected to Africa. The Nile river valley, which runs from East Africa to the Mediterranean Sea served as a bidirectional corridor in the Sahara desert, that frequently connected people from Sub-Saharan Africa with the peoples of Eurasia.

North African admixture

The Y haplogroup E1b1b1b (E-M81) is seen as a marker of Northern African migration into Southern Europe, at least some of which may have happened in recent millennia.

In Europe, E1b1b1b (E-M81) is found everywhere but mostly in the Iberian Peninsula, where it is more common than E-M78 unlike in the rest of Europe at an average frequency of 4-5.6%, with frequencies reaching 9% in Galicia, 10% in Western Andalusia and Northwest Castile and 13 % in Cantabria. The highest frequency of this clade found so far in Europe has been observed at 40% the Pasiegos from Cantabria.

E-M81 is also found in Sicily, and in slightly lower frequencies in continental Italy (especially near Lucera) and France, possibly due to ancient migrations during the Islamic, Roman, and Carthaginian empires, as well as the influence of Sephardic Jews.

Flores et al. (2004) propose that the absence of microsatellite variation suggests a very recent arrival from North Africa consistent with historical exchanges across the Mediterranean during the period of Islamic expansion, namely of Berber populations .

In a study of Portuguese Y-chromosome lineages, Gonçalves et al. (2005) revealed that "The mtDNA and Y data indicate that the Berber presence in that region dates prior to the Moorish expansion in 711 AD... Our data indicate that male Berbers, unlike sub-Saharan immigrants, constituted a long-lasting and continuous community in the country".

A very recent study about Sicily by Gaetano et al. (2008) found that "The Hg E3b1b-M81, widely diffused in northwestern African populations, is estimated to contribute to the Sicilian gene pool at a rate of 6%." and "confirms the genetic affinity between Sicily and North Africa".

According to one recent study (by Adams et al., December 2008) that analysed 1140 unrelated Y-chromosome samples in Iberia "mean North African admixture is 10.6%, with wide geographical variation, ranging from zero in Gascony to 21.7% in Northwest Castile".

Apart from E-M81, other related haplogroups within the E-M35 clade are also seen as showing immigration from Northern Africa. Cruciani et al. (2007) using 6,501 unrelated Y-chromosome samples from 81 populations found that: "Considering both these E-M78 sub-haplogroups (E-V12, E-V22, E-V65) and the E-M81 haplogroup, the contribution of northern African lineages to the entire male gene pool of Iberia (barring Pasiegos), continental Italy and Sicily can be estimated as 5.6%, 3.6%, and 6.6%, respectively."

In January 2009, a study by Capelli et al. that analysed 717 Spanish individuals, 659 Portuguese individuals and 915 Italian individuals found North African haplogroups frequencies at 7.7 % in Spain (ranging from 0% in Catalonia to 18.6% in Cantabria), 7.5% in Sicily, 7.1% in Portugal and 4.7% and in a region of Southern Italy (East Campania, Northwest Apulia, Lucera).

Genetic studies on Iberian populations also show that North African mitochondrial DNA sequences (haplogroup U6) and sub-Saharan sequences (Haplogroup L), although present at only low levels, are still at much higher levels than those generally observed elsewhere in Europe. Haplotype U6 have also been detected in Sicily at very low levels. It happens also to be a characteristic genetic marker of the Saami populations of Northern Scandinavia. It is difficult to ascertain that U6's presence is the consequence of Islam's expansion into Europe during the Middle Ages, particularly because it is more frequent in the north of the Iberian Peninsula rather than in the south. In smaller numbers it is also attested too in the British Islands, again at their northern and western borders. It may be a trace of a prehistoric neolithic/megalithic expansion along the Atlantic coasts from North Africa, perhaps in conjunction with seaborne trade. One subclade of U6 is particularly common among Canarian Spaniards as a result of native Guanche (proto-Berber) ancestry.

Recent Sub Saharan Admixture admixture

Further information: Sub-Saharan DNA admixture in Europe

Sub-Saharan African Y-chromosomes that date to the period after Neolithic are much less common in Europe. The re-desertification of the Sahara about 5,000 years ago forced African farmers living in the Sahel to migrate South and West rather than to the North towards Eurasia. Until the Age of Exploration and the European exploration of Africa in the 15th century CE, Sub-Saharan Africa remained isolated from Europe. Consequently the presence of African haplogroups in Europe such as Haplogroups E(xE3b) (i.e. clades of E other than E3b) and Haplogroup A have been attributed to periods following the beginning of the Atlantic Slave Trade. The Moorish invasion of Iberia may also have introduced Sub-Saharan African admixture into Europe. Haplogroup A has been detected in Yorkshire, Portugal (3%), France (2.5% in a very small sample), Germany (2%), Sardinia (1.6%), Austria (0.78%), Italy (0.45%), Spain (0.42%), Greece (0.27%) Cyprus and Turkey.. North Africans have about 5% paternal sub-Saharan admixture.

African Mitochondrial haplogroups are distributed along a west-to-east cline and a south-to-north cline. The highest frequencies are observed in the Iberian Peninsula.

Malyarchuk et al. identified 8 African haplogroups in Russians, Czechs, Slovaks and Polish populations. These haplogroups included L1b, L2a, L3b, L3d and M1, of which L1b, L3b1, L3d appeared to be of West African origin. Haplogroup L2a1a was identified as most likely having entered Europe about 10,000 years ago, possibly through the Iberian Peninsula.

Haplogroup M1 is also found in Europe at low frequencies, but it is not uncommon in Southern Europe. In a study by Gonzalez et al 2007, haplogroup M1 had an overall frequency of 0.3% in the samples that were analyzed. The highest frequencies were found in Sicily where 3.8% of the population were members of haplogroup M1. The origins of haplogroup M1 have yet to be conclusively established. However, one clade of haplgroup M1, M1a is widely accepted to be of East African origin. About 40% of all clades of M1 found in Europe are M1a and consequently of recent East African origin.

Inferences from ancient DNA

The genetic history of Europe has mostly been reconstructed from the modern populations of Europe, assuming genetic continuity. This is because of availability of data. However, a small number of ancient mtDNA analyses are available from both the historical and prehistorical periods. These have been summarised by Ellen Levy-Coffman in the Journal of Genetic Genealogy. There are some large differences in the frequencies of occurrence of the various haplogroups compared wth the modern population.

For example, mtDNA Haplogroup N1a, while presently rare (0.18%-0.3%), occurred in as many as 25% of Neolithic Europeans. . The cause of this reduction is unknown.

She concludes that the genetic profile of Europe has undergone significant transformation over time and that the modern population is not a living fossil of the ancient one. However, the very small sample sizes of the ancient DNA are a problem and more data is needed.

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• Luca Cavalli-Sforza http://www.pnas.org/cgi/content/full/94/15/7719 Genes, peoples, and languages - Cavalli-Sforza 94 (15): 7719 - Proceedings of the National Academy of Sciences
• Perlès C, Monthel G ( 2001) The Early Neolithic in Greece: The First Farming Communities in Europe. Cambridge University Press, Cambridge.
• Runnels C (2003) The origins of the Greek Neolithic: a personal view, in Ammerman and Biagi (2003 eds).

See also

• Caucasoid
• European ethnic groups
• Human genetic variation
• Population genetics
• Archaeogenetics of the Near East
• White people
• Genetic history of the British Isles

External links

• International Society of Genetic Genealogy - 2009 tree of haplogroup R
• Journal of Genetic Genealogy - We Are Not Our Ancestors: Evidence for Discontinuity between Prehistoric and Modern Europeans
• Atlas of the Human Journey
• World Haplogroups Maps
• Origins of Europeans
• Genetic Structure of Human Populations.
• Haplotype R1b
• Haplogroup R1b