Genetic history of Europe

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This section describes demographic and genetic flow into Europe. For a broader, more detailed view of Human migrations, see that article. For a global perspective on this topic, see Atlas of the Human Journey,World Haplogroups Maps, Origins of Europeans and Genetic Structure of Human Populations.

[edit] Haplogroups

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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 haplogroups which largely account for most of Europe's present-day population.

• Haplogroup R1b is common on the western Atlantic coast of Europe from Spain to Scotland.
• Haplogroup I is common across central Europe and up into Scandinavia.
• Haplogroup R1a is common in eastern Europe and has also spread across into central Asia and as far as India and Pakistan.^{[1] [2]}

Most common of all haplogroups among western Europeans is R1b.^{[3] [4]} The exact following values of Hg R1b are: Basques: 88.1%; Irish: 81.5%; Welsh: 89.0%; Scots: 77.1%; Non-Basque Spaniards: 68.0; Catalans: 79,2; Andalusians: 65,5; Portuguese(South): 56.0%; Portuguese (North): 62.0%; British: 68.8; English (Central): 61.9% Belgians: 63.0; French: 52.2; Danes: 41.7%, Norwegian: 25.9; Swedish: 20.0; German: 47.9; Italian (Calabria): 32.4; Italian (Sardinia): 22.1%; Italian (North-central): 62.0. In conclusion, the so-called R1b genetic family is the most numerous in Western Europe. ^[5] Each haplogroup also have subclades. ^[6] R1a and R1b are subclades of Haplogroup R (Y-DNA) ^[7] Two main subgroups of Haplogroup I (Y-DNA) are I-M253/I-M307/I-P30/I-P40 which has highest frequency in Scandinavia, Iceland, and northwest Europe. The other is I-S31 which 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.^[8]

There is an ongoing debate regarding Neolithic Europe, with evidence both for and against a demic diffusion from the Near East: 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.^{[9] [10][11]}

A little later, around 4,500 years ago, Haplogroup N3 began moving across from west of the Ural mountains. Haplogroup N3 follows closely the spread of the Finno-Ugric languages.^[1]

About mtDNA (Mitochondrial DNA), according to University of Oulu Library (Finland):

[edit] European Population Substructure

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European population substructure, using Single nucleotide polymorphisms

An autosomal DNA plot of genetic distances derived from 120 allele frequencies in Cavalli-Sforza's The History and Geography of Human Genes.

In 2006, a study by 9 scientists made an analysis comparing different individuals from European ancestry groups. They concluded that "there is a consistent and reproducible distinction between “northern” and “southern” European population groups" ^[13]

While above scientists claimed that the people of British Isles cluster with Northern Europeans Stephen Oppenheimer stated: "By far the majority of male gene types in the British Isles derive from Iberia (Spain and Portugal)" ^[14]

Bryan Sykes, also stated that "The genetic evidence shows that a large proportion of Irish Celts, on both the male and female side, did arrive from Iberia at or the same time as farming reached the Isles" ^[15]

A recent genetic piece of research from 2007 claims: "The Spanish and Basque groups are the furthest away from other (European) continental groups, which is consistent with the suggestions that the Iberian peninsula holds the most ancient European genetic ancestry". The same study also found "several significant axes of stratification, most prominently in a North-Southeastern trend but also along an East-West axis." They also confirmed English and Irish cluster with Northern Europeans such as Germans and Poles while some Basque and Italian individuals also clustered with Northern Europeans. Despite these stratifications, they also said: "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." ^[16]

[edit] Paleolithic

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.^{[citation needed]} Much of this research is ongoing, with discoveries still being continually made, and theories rise and fall.

Europe 20,000 years ago, showing coastline, extent of Ice caps and regions where refugia are thought to have been situated.^[17]

Modern humans began to colonize Europe about 35,000 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.^{[citation needed]} Very quickly—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.^[18] About 22,000 years ago the last Ice Age (often referred to as the Last Glacial Maximum or LGM) began, rendering much of Europe uninhabitable.^{[citation needed]} Humans may only have occupied certain regions of Europe at this time, these are often called refuges (or refugia) and were located along the northern Mediterranean and Black Sea coasts, as well as in the Balkans. When the glaciers receded about 16,000 years ago, the populations that had occupied the refuges are thought to have begun to spread and colonise northern Europe.^[19][20] The population of Europe were hunter-gatherers until the advent of agriculture about eight millennia ago, some academics theorise that farming was introduced by people who migrated (Demic diffusion) from the Near East, and that these farmers introduced Indo-European languages to Europe. Anatolian hypothesis proponents have emphasized that "demic diffusion" is not necessary to explain most of the spread of Indo-European languages in Europe or elsewhere. ^[21]

[edit] Indo-Europeans

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Theories about the origins of the Indo-European language center 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 spread their culture and genes across Europe. It has been difficult to identify what these "Kurgan" genes might be.

Another approach -- the Anatolian or Danubian hypthesis -- hypothesizes that possibly Indo-European languages originated in Anatolia or that the proto-language was spoken by early food producing communities along the Danube that can archaeologically be traced to Anatolia sometime between 6000–4000 BCE. The language would have been intoduced to local populations, at the same time these migrants brought the first domesticated animals and plants to Europe, through the introduction of food production technology and economy (agriculture) and the accompanying change in culture. (See, e.g., Renfrew, C. 1996, Language families and the spread of farming, in The Origins and Spread of Agriculture and Pastoralism, ed. Harris, D.R. 1996 UCL Press.) To what extent they 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.^[22]

[edit] Uralic Influence

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According to a study conducted by four scientists, including Cavalli-Sforza LL:

[edit] North and Northeast African influences

There are a number of genetic markers which are characteristic of Horn African and North African populations which are to be found in European populations signifying ancient and modern population movements across the Mediterranean. These markers are to be found particularly in Mediterranean Europe but some are also prevalent, at low levels, throughout the continent.

The general parent Y-chromosome Haplogroup E3b, originating in modern day Somalia, is by far the most common in North and Northeast Africa, and is also common throughout the majority of Europe, particularly in Mediterranean and South Eastern Europe, reaching its highest concentration in Greece and the Balkan region, but also with an important presence in other countries such as Hungary, Italy, Iberia and Austria. [15].^[24] Nevertheless, the presence of haplogroup E3b is principally the result of Neolithic migrations from Anatolia across the Bosphorous rather than of more recent exchanges across the Mediterranean.^[24] mtDNA, the most common "European" subclade of Haplogroup E3b, being E-M78, present throughout continental Europe.

However, Y-chromosome haplotype E-M81, a derivative of Haplotype E3b, is specific to North African populations and absent in Europe except for Iberia (Spain and Portugal) and 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.^[24] Genetic studies on Iberian populations also show that North African sequences (haplogroup U6) and sub-Saharan sequences (Haplogroup L), present values which are a little higher than those generally observed in Europe, although very low levels of Haplotype U6 have also been detected in Sicily. It happens also to be a characteristic genetic marker of the Saami populations of Northern Scandinavia.[16] It is difficult to ascertain that U6's presence is the consequence of Islam's expansion in Europe during the Middle Ages, particularly because it is more frequent in the north of the peninsula rather than in the south. It may also be the result of neolithic expansion from North Africa. One subclade of U6 is particularly common among Canarian Spaniards as a result of native Guanche (proto-berber) ancestry.

On the other hand, the distribution of mtDNA Haplogroup L, is consistent with modern historical data, being more frequent in Iberia than in the rest of Europe and more frequent in the south of the peninsula than in the north. Islamic domination, as well as the slave trade, is likely to have been a factor leading to its presence in some modern-day Southern Iberian populations. Haplotype 5 (p49/TaqI), common in Morocco, may be also found in the Iberian peninsula, and a decreasing North-South cline of frequency clearly establishes a gene flow from North Africa towards Iberia which is also consistent with Moorish presence in the peninsula.[17]. It should be noted though that said study takes into account only one genetic marker.

Recent studies that take into account multiple pieces of research and up to eight different genetic markers, including autosomal, mitocondrial and Y-chromosome DNA, have come to different conclusions as to the extent of this influence. See IberiaS (Spain) in the European context. [18] [19].

This particular article concluded that no significant correlation is apparent between North African admixture and geography. Genetic exchanges across the Mediterranean Sea, and especially in its western-most part where the geographic distance between continents is smallest (Spain), seem to have been limited or very limited (Simoni et al. 1999; Bosch et al. 2001). Nevertheless, a very recent study that take into account new markers apart from Haplotype 5 "North African Berber and Arab influences in the western Mediterranean" (Dieterlen et Florent. 2006) clearly showed the genetic exchanges have been quite important [20].

[edit] Other Sub-Saharan Africans

See also: Sub-Saharan DNA admixture in Europe

Finally, aside from E3b, sub-Saharan African DNA is scattered throughout the European continent. Not every population has been studied yet, but enough have so that a picture is starting to emerge. The amount of black admixture in Europe today ranges from a few percent in Iberia to almost nil around the Baltic.^[25] It seems to show a decreasing cline from the southwest to the northeast, which corresponds with the areas most affected by the African slave trade.

According to a summary study by Pereira et al. 2005, sub-Saharan mtDNA L haplogroups were found at rates of 3.83% in Iberians (Portuguese and Spanish), 2.86% in Sardinians, 2.38% in Albanians, 1% in the British, 0.94% in Sicilians, 0.62% in a German-Danish sample.

Sub-Saharan African Y-chromosomes are much less common in Europe, for the reasons discussed above. However, Haplogroups E(xE3b) and Haplogroup A spread to Europe due to migrations from Northeast Africa, rather than the slave trade. Haplotype A has been detected in Portugal (3%), Spain (0.42%), Germany (2%), Austria (0.78%), France (2.5% in a very small sample), Italy (0.45%), Sardinia (1.6%) and Greece (0.27%). By contrast, North Africans have about 5% paternal West African admixture,^[26] and are about of 75% paternal East African descent^[27]

[edit] Footnotes

1. ^ ^{a b} DNA Heritage [1]
2. ^ Semino et al (2000),The Genetic Legacy of Paleolithic Homo sapiens sapiens in Extant Europeans, Science Vol 290
   Note: Haplogroup names are different in this article. For ex: Haplogroup I is referred as M170
3. ^ World haplogroup maps [2]
4. ^ Y-chromosome DNA Haplogroups [3]
5. ^ Oxford Journals [4]
6. ^ Y-DNA Haplogroup Tree 2006 [5]
7. ^ Y-DNA Haplogroup R and its Subclades [6]
8. ^ Y-DNA Haplogroup I and its Subclades [7]
9. ^ Population genetics: DNAs from the European Neolithic [8]
10. ^
11. ^ [9][10]
12. ^ Mitochondrial DNA sequence variation in human populations, Oulu University Library (Finland) [11]
13. ^ "most individual participants with southern European ancestry (Italian, Greek, 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." Based on this work, we have developed a core set of informative SNP markers that can control for this partition in European population structure in a variety of clinical and genetic studies." European Population Substructure: Clustering of Northern and Southern Populations [12]
14. ^ On average only 30% of gene types in England derive from north-west Europe. Even without dating the earlier waves of north-west European immigration, this invalidates the Anglo-Saxon wipeout theory... ...75-95% of British Isles (genetic) matches derive from Iberia... Oppenheimer, "Origins of the British" (pages 375 and 378)
15. ^ Here again, the strongest signal is a Celtic one, in the form of the clan of Oisin, which dominates the scene all over the Isles. The predominance in every part of the Isles of the Atlantic chromosome (the most frequent in the Oisin clan), with its strong affinities to Iberia, along with other matches and the evidence from the maternal side convinces me that it is from this direction that we must look for the origin of Oisin and the great majority of our Y-chromosomes. The sea routes of the Atlantic fringe conveyed both men and women to the Isles. Sykes, "Blood of the Isles" (2006), Pages 281,282,283
16. ^ Measuring European Population Stratification using Microarray Genotype Data [13]
17. ^ Coastline sketched from Mithen (2003) pp. 108-109, Extent of refugia infered from Oppenheimer (2006) p. 103.
18. ^ Richard G. Klein (March 2003). "PALEOANTHROPOLOGY: Whither the Neanderthals?". Science 299 (5612): 1525-1527. DOI:10.1126/science.1082025.
19. ^ Antonio Torroni et al. "A Signal, from human mtDNA, of Postgalcian Recolonization in Europe, Am. J. Human Gen.69:844-852 (2001)
20. ^ Ornella Semin et al. The Genetic Legacy of Paleolithic Homo Sapiens Sapiens in Extant Europeans: A Y Chromosome Perspective Science 290:1155-1159, 2000.
21. ^ Nicholas Wade, "Before the Dawn" ISBN 1594200793 , ch. 10.
22. ^ See Bryan Sykes, The Seven Daughters of Eve, 1st American ed. (New York: Norton, 2001) for an entertaining account of how this consensus was reached. For historical reasons, in the 1980s mtDNA researchers believed that the Indo-European expansion was overwhelmingly a spread of technology and language, not of genes, while the those who studied Y-chromosome lineages believed the opposite. Gradually the mtDNA guys (Sykes) admitted more physical migration into their scenarios, while the Y folks (Peter Underhill) accepted more technology-copying. Eventually, both groups independently reached a 20% Neolithic - 80% Paleolithic ratio of genetic contribution to today's European population. The mtDNA vs. Y discrepancy is explained by noting that in such conquest-based migrations, a common pattern is invading foreign males producing offspring with indigenous females, though significant numbers of females of the spreading culture would also arrive with post-conquest settlers. However, where migrations are essentially economic (as most migrations appear to be) the scenario of male family members preceding females into new territory looking for opportunities is equally probable.
23. ^ Uralic genes in Europe by Guglielmino CR, Piazza A, Menozzi P, Cavalli-Sforza LL [14]
24. ^ ^{a b c} *Semino et al. (2004) Origin, Diffusion, and Differentiation of Y-Chromosome Haplogroups E and J: Inferences on the Neolithization of Europe and Later Migratory Events in the Mediterranean Area
25. ^ Pereira et al. 2005 (view the specific data here)
26. ^ Cruciani et al. 2004, Flores et al. 2004, Brion et al. 2005, Brion et al. 2004, Rosser et al. 2000, Semino et al. 2004, and DiGiacomo et al. 2003
27. ^ Bosch et al. 2001 High-Resolution Analysis of Human Y-Chromosome Variation Shows a Sharp Discontinuity and Limited Gene Flow between Northwestern Africa and the Iberian Peninsula

[edit] External links

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