Genetic history of the British Isles

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The genetic history of the British Isles is the subject of research within the larger field of human population genetics. It has developed in parallel with DNA testing technologies capable of identifying genetic similarities and differences between populations. The conclusions of population genetics regarding the British Isles, in turn draw upon and contribute to the larger field of understanding the history of humanity in the British Isles generally, complementing work in linguistics, archeology, history and genealogy.

Research concerning the most important routes of migration into the British Isles is the subject of debate. Apart from the most obvious route across the narrowest point of the English Channel into Kent, other routes may have been important over the millennia, including a land bridge in the Mesolithic period, and also maritime connections along the Atlantic coast.

In addition, the periods of the most important migrations are also contested. While the Neolithic introduction of farming technologies from Europe is frequently proposed as a period of major population change in the British Isles, such technology could either have been learned by locals from a small number of immigrants, or may have been put into effect by colonists who significantly changed the population.

Other potentially important historical periods of migration which have been subject to consideration in this field include the introduction of Celtic languages and technologies (during the Bronze and Iron Ages), the Roman era, the period of Anglo-Saxon influx, the Viking era, the Norman invasion of 1066 and the era of European wars of religion. There are also similarly many potential eras of movement between different parts of the British Isles.

Research projects and influential publications[edit]

An international watershed in the publication and discussion of genetic evidence for ancient movements of people was that of Luigi Luca Cavalli-Sforza who used polymorphisms from proteins found within human blood (such as the ABO blood groups, Rhesus blood antigens, HLA loci, immunoglobulins, G-6-P-D isoenzymes, amongst others).[1] One of the lasting proposals of this study with regards to Europe is that within most of the continent, the majority of genetic diversity may best be explained by immigration coming from the southeast towards the northwest or in other words from the Middle East towards Britain and Ireland. He proposed at the time that the invention of agriculture might be the best explanation for this.

Later published studies used mitochondrial DNA to study the female line of descent. It became possible to use Y chromosome DNA to study male descent. As opposed to large scale sampling within the genome, Y DNA and mitochondrial DNA represent specific types of genetic descent and can therefore reflect only particular aspects of past human movement.

For Britain, major research projects aimed at collecting more data include the Oxford Genetic Atlas Project (OGAP), which was associated with Bryan Sykes of Oxford University and more recently the People of the British Isles, also associated with Oxford.[2]

Earliest people[edit]

In 2007 Bryan Sykes produced an analysis of 6000 samples from the OGAP project in his book Blood of the Isles.[3] Later, Stephen Oppenheimer in his 2006 book The Origins of the British used the data from Weale et al. (2002), Capelli et al. (2003) and Rosser et al. (2000) for Europe. In opposition to Mesolithic origin theories, Sykes and Oppenheimer argued for significant immigration from the Iberian peninsula into Britain and Ireland. Much of this argument depended on Y DNA evidence. By 2010 several major Y DNA studies presented more complete data, showing that nearly all of the Y DNA subclades in Britain arrived very recently through Celtic and Germanic migrations from central and northern Europe during the Bronze Age, with most of the Mesolithic ancestry (I-M253) arriving from Scandinavia.[4][5][6]

In 2012, from a highly enlarged whole-genome mitochondrial database published, the authors concluded that the most archaic mtDNA lineages in Europe came from a Middle Eastern migration into Europe during the Late Glacial period, ~19–12 thousand years ago and not as late as the Neolithic as was previously proposed.[7] They argued that this population came from a previously contracted European population refugium on the Anatolian Plateau which spread to three further refugia, Franco-Cantabria, the Italian Peninsula and the East European Plain. From these three areas the lineages would then have repopulated Europe.

Germanic & Scandinavian genetics[edit]

Another subject in the literature which has been widely discussed is whether genetics can show signs of Germanic invasions particularly in England. In a widely cited article through DNA testing, Weale et al. (2002) argued that the Y DNA data showed signs of a racial "apartheid" in Anglo-Saxon England. The signatures of Germanic influx to England is now widely accepted and has been shown in other studies, such as Capelli et al. (2003). The Capelli study, with higher sample numbers, gave much lower frequencies of "Germanic" genetic markers in England than did Weale. They describe such markers as typically ranging between 20% and 40%, with York forming an outlier at 60%. Most of Scotland showed a very similar genetic composition to England. North German/Danish genetic frequencies were indistinguishable, thus precluding any ability to distinguish between the genetic influence of the Anglo-Saxon source populations and the later, and better documented, influx of Danish Vikings.[8]

A study into the Norwegian Viking ancestry of British people found that there is evidence of particular concentrations in several areas; especially in Lowland and Eastern Scotland - and the north sea islands Shetland and Orkney, Western Scotland and the Western Isles including Skye in Scotland, Anglesey in Wales, the Isle of Man, and the Wirral, Mid-Cheshire, West Lancashire and Cumbria in England.[9][10][11][12]

Irish population[edit]

In Ireland population genetic studies have been undertaken by a team under Dan Bradley, including surname studies. Databases on Britain and Ireland, as well as on various surnames are being built up from personal DNA tests, for example at FamilyTree DNA. A widely reported article in this area was Moore et al. (2006), which provided Y DNA evidence that in some cases Irish surname groups were highly dominated by single male lines, presumed to be those of dynastic founders such as Niall of the Nine Hostages.

Recently use has been made of technologies which can test hundreds of thousands of possible mutation points (SNPs) in the rest of the human genome (the autosomal DNA). The results of these large studies have shown that the main patterns of relatedness between European populations are simply geographical, meaning that the British and Irish are simply most genetically related to the people in neighboring countries. This has not yet led to any new theories concerning migrations.[13]

It has been proposed that Y chromosome diversity tends to change more quickly than the overall population, because at least sometimes, some male lines move more quickly than the general population, meaning that the most common Y chromosomes in areas will reflect relatively recent "waves" of human movement.[14]

Mitochondrial DNA[edit]

In 2007, Bryan Sykes broke mitochondrial results into twelve haplogroups for various regions of the Isles. He has given maps and proposals concerning ancient migrations for Ireland, Scotland, Wales and England.

Sykes and Oppenheimer have each given nicknames to various haplogroups to allow easier recognition, including the principal ones in the Isles. Below the normal scientific names are given, followed by the popularized "clan names" of Sykes, and in some cases also of Oppenheimer:-

mtDNA

...and within U...

Sykes found that the maternal clan (haplogroup) pattern was similar throughout England but with a definite trend from east and north to the south and west. The minor clans are mainly found in the east of England. Sykes found Haplogroup H to be dominant in Ireland and Wales. A few differences were found between north, mid and south Wales. There was a closer link between north and mid Wales than either had with the south.

Sykes found that 10% of the Irish population were in Haplogroup U5 called Ursula. He calculated a date of 7300 BC for the entry of this lineage into Ireland. Similar dates were proposed for the other mitochondrial haplogroups, implying that mitochondrial lines in Ireland are far older there than the arrival of Iron Age Celts. Little difference was found between the maternal clans in the four provinces.

Y DNA[edit]

In 2007, Bryan Sykes produced an analysis of 6000 samples from the OGAP project in his book Blood of the Isles.[3] designating five main Y-DNA haplogroups for various regions of the Isles. As with mitochondrial haplogroups not only Sykes but also Stephen Oppenheimer chose to popularize the concept by giving them "clan names". The following gives their normal scientific names.[15]

  • Haplogroup R1b (Y-DNA). Oisin (Sykes), Ruisko (Oppenheimer). Oppenheimer attempted to divide this in 16 clusters.[16]
  • Haplogroup I (Y-DNA). Wodan (Sykes), Ivan (Oppenheimer). Oppenheimer was able to divide this into 3 clear clusters. The two most important were
  • I1 (Ian)
  • I2 (Ingert), now known as I2b or I2a2[17]

The larger Haplogroup R1b (Y-DNA) is dominant in Western Europe, not only Britain and Ireland. While it was once seen as a lineage connecting the British Isles to Iberia (where it is also common) opinions concerning its origins have changed, it is now known R1b and R1a entered Europe with Indo-European migrants likely originating around the Black sea,[18] R1 is now the most common haplotype in Europe. The most common R1b subclade in England is R1b-S21 ("Germanic"), which is common in the North Sea areas such as the Netherlands and Denmark, whereas Ireland is dominated by R1b-L21 ("Celtic"), which is found mainly in France on continental Europe.[19][20][21][22]

There are various smaller and geographically well defined Y-DNA Haplogroups under R1b in Western Europe.

Haplogroup I is a grouping of several quite distantly related lineages. These may be the only pre-Neolithic Y lineages left in Europe.[23] Looking at the three main clusters, according to Rootsi et al.,[23] with up-dated nomenclature according ISOGG:[17]-

  • I1a in Rootsi et al., now known as I1, is mainly associated with Scandinavia in modern populations and is common in several parts of England, reaching as high in eastern England as it does in Scandinavia.
  • I1b in Rootsi et al., now known as I2a is associated with the Balkans and is not common in Britain and Ireland.
  • I1c in Rootsi et al., now known as I2b is less clearly associated with any particular part of Europe.

Haplogroup R1a, a distant cousin of R1b, it is most common in Eastern Europe. In Britain it is associated with Scandinavian immigration during periods of Viking settlement, 25% of men in Norway belong to this haplogroup, it is much more common in Norway than the rest of Scandinavia. Around 9% of all Scottish men belong to the Norwegian R1a subclade, which peaks at over 30% in Shetland and Orkney.[24]

Haplogroups E1b1b and J in Europe are regarded as markers of Neolithic movements from the middle east to southern Europe and likely to Northern Europe from there. These haplogroups are most often found in Southern Europe and North Africa. Both are rare in Northern Europe, E1b1b is found in 1% of Norwegian men, 1.5% of Scottish, 2% of English, 2.5% of Danish, 3% of Swedish, and 5.5% of German. It reaches its peak in Europe in Kosovo at 47.5% and Greece at 30%.[25][26]

Uncommon Y haplogroups[edit]

Geneticists have found that seven men with a rare Yorkshire surname (suppressed due to privacy concerns) carry a genetic signature previously found only in people of African origin. All the men had haplogroup A1, a Y chromosome genetic marker which is west African specific. Haplogroup A1 is rare and has only ever been found 25 times, again only in people of African origin. Haplogroup A1 is a subclade of Haplogroup A which geneticists believe originated in Eastern or Southern Africa.[27]

The individuals had no knowledge of any African heritage in their family. The researchers wondered if the presence of this haplogroup in Yorkshire could stem from the recruitment of Africans for the construction of Hadrian's Wall by the Romans or result from intermarriage with an African slave, some of whom rose quite high in society.[27] According to Bryan Sykes, some English people's genetics suggest that they are "descended from north African, Middle Eastern and Roman clans", and that "although the Romans ruled from AD 43 until 410, they left a tiny genetic footprint."[28]

In the North Wales town of Abergele there is a very high percentage of haplogroup E1b1b1 (33%), which is thought to have dispersed around Europe mainly from the Balkans.[26]

Geneticists have shown that former American president Thomas Jefferson, who might have been of Welsh descent, along with two other British men out of 85 British men with the surname Jefferson, carry the rare Y chromosome marker T which is typically found in East Africa and the Middle East. It is also found in 4.5% of Greek men, 3.5% of Estonian, and 2.5% of Spanish and Italian men. There has been no other documented cases of Haplogroup T occurring in Northern Europe other than those two cases. The presence of scattered and diverse European haplotypes within the network is nonetheless consistent with Jefferson's patrilineage belonging to an ancient and rare indigenous European type.[29]

See also[edit]

References[edit]

Notes
  1. ^ Cavalli-Sforza (1997)
  2. ^ The People of The British Isles website
  3. ^ a b Sykes (2001)
  4. ^ Eupedia Y DNA subclade maps
  5. ^ Y DNA haplotypes by country
  6. ^ Red hair a Celto-Germanic trait
  7. ^ Pala et al. 2012 Mitochondrial DNA signals of late glacial recolonization of Europe from near eastern refugia. http://europepmc.org/abstract/MED/22560092/reload=0;jsessionid=Ex1l76DwTiCwb3huDcM9.6
  8. ^ Capelli et al. (2003), p.983
  9. ^ Excavating Past Population Structures by Surname-Based Sampling: The Genetic Legacy of the Vikings in Northwest England
  10. ^ Goodacre, S; Helgason, A; Nicholson, J; Southam, L; Ferguson, L; Hickey, E; Vega, E; Stefánsson, K; Ward, R; Sykes, B (2005). "Genetic evidence for a family-based Scandinavian settlement of Shetland and Orkney during the Viking periods". Heredity 95 (2): 129–135. doi:10.1038/sj.hdy.6800661. PMID 15815712. 
  11. ^ "Gene geography: Do you have Viking ancestry in your DNA?". Wellcome Trust. 2004. Retrieved 9 January 2010. 
  12. ^ Branagan, Mark (30 January 2009). "'Time team' to seek out genetic secrets of Yorkshire's Viking past". Yorkshire Post. Retrieved 9 January 2010. 
  13. ^ O'Dushlaine et al. (2010a); O'Dushlaine et al. (2010b)
  14. ^ Chiaroni et al. (2009)
  15. ^ ISOGG website
  16. ^ See Campbell (2007) for an attempt to "deconstruct" these.
  17. ^ a b "ISOGG 2011 Y-DNA Haplogroup I". Isogg.org. Retrieved 2011-09-16. 
  18. ^ Y DNA haplotypes by country
  19. ^ Eupedia Y DNA subclade maps
  20. ^ Balaresque et al. (2010)
  21. ^ Myres et al. (2011)
  22. ^ Cruciani et al. (2011)
  23. ^ a b Rootsi et al. (2004)
  24. ^ Bowden et al. (2008)
  25. ^ Eupedia Y DNA subclade maps
  26. ^ a b Cruciani et al. (2007)
  27. ^ a b King et al. (2007a)
  28. ^ "Ancient Britons come mainly from Spain". Evening Standard. September 20, 2006. Retrieved June 23, 2012. 
  29. ^ King et al. (2007b)
Literature

Further reading[edit]