Genetic history of the British Isles

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.

Contents

Research projects and influential publications

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 Europe, 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 farming 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 Brian Sykes of Oxford University and more recently the People of the British Isles, also associated with Oxford.[2]

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 Neolithic origin theories, which remain strong, Sykes and Oppenheimer argued for significant immigration from Iberia into Britain and Ireland. Much of this argument was based upon Y DNA evidence, however by 2010 several major Y DNA studies presented more complete data, showing that the oldest-surviving male lineages had mostly migrated to Britain from the Balkans, and ultimately from the Middle East, not from Iberia.[4][5][6]

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 but not unanimously accepted article, Weale et al. (2002) went as far as arguing that the Y DNA data showed signs of a racial "apartheid" in Anglo-Saxon England. That there are relatively clear signs of Germanic contact in parts of Britain is accepted and shown in other studies such as Capelli et al. (2003).

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 FamilyTreeDNA. 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.[7][8]

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.[9]

Mitochondrial DNA

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 that 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

Main article: Y-DNA haplogroups in European populations

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.[10]

  • I1 (Ian)
  • I2 (Ingert), now known as I2b[11]

Haplogroup R1b 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, with estimates of age tending to go down from Palaeolithic to Neolithic or even younger and analysis of the branching within this line now being seen to support the view that at least concerning the majority of R1b in Europe, it has its roots in the Middle East and has spread northwestward from there. The R1b types found in Britain and Ireland are dominated by R-P312, which on the continent is found mainly west of the Rhine but at least in England there is also a significant presence of R-U106, which is found east of the Rhine and also in North Sea areas such as Denmark and Holland.[4][5][6]

Haplogroup I is a grouping of several quite distantly related lineages. These may be the only pre-Neolithic Y lineages left in Europe.[12] Looking at the three main clusters, according to Rootsi et al. (2004), with up-dated nomenclature according ISOGG:[11]-

Haplogroup R1a, a distant cousin of R1b, is most common from Eastern Europe to India. In Britain it is associated with probable Scandinavian immigration during periods of Viking settlement.[13]

Haplogroups E1b1b and J in Europe are regarded as markers of movements from southeastern Europe to northwestern and therefore as a potential markers of introduced technology such as farming.[14] At least in the case of E1b1b a more recent Roman era move from the Mediterranean area has been proposed by Bird (2007).

Uncommon Y haplogroups

Geneticists have found that seven men with a rare Yorkshire surname 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. 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.[15] 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."[16]

In the North Welsh 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.[14]

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. Haplogroup T is rare in Europe but phylogenetic network analysis of its Y-STR (short tandem repeat) haplotype shows that it is most closely related to an Egyptian T haplotype. 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.[17]

See also

Molecular Anthropology portal
Evolutionary biology portal

External links

References

Notes
  1. ^ Cavalli-Sforza (1997)
  2. ^ The People of The British Isles website
  3. ^ a b Sykes (2001)
  4. ^ a b Balaresque et al. (2010)
  5. ^ a b Myres (2010)
  6. ^ a b Cruciani et al. (2010)
  7. ^ O'Dushlaine et al. (2010a)
  8. ^ O'Dushlaine et al. (2010b)
  9. ^ Chiaroni et al. (2009)
  10. ^ ISOGG website
  11. ^ a b "ISOGG 2011 Y-DNA Haplogroup I". Isogg.org. http://www.isogg.org/tree/ISOGG_HapgrpI.html. Retrieved 2011-09-16. 
  12. ^ Rootsi et al. (2004)
  13. ^ Bowden et al. (2008)
  14. ^ a b Cruciani et al. (2007)
  15. ^ King et al. (2007)
  16. ^ http://www.thisislondon.co.uk/news/article-23367572-ancient-britons-come-mainly-from-spain.do
  17. ^ King et al. (2007b)

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