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 coasts.
The periods of the most important migrations are contested. 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 by colonists who significantly changed the population. Analysis of nuclear DNA from Mesolithic and Neolithic individuals suggests that the best model is of near-total replacement of the British Mesolithic population by seaborne neolithic Europeans whose ancestry came mostly from Anatolia (about 75%) and European hunter-gatherers (about 25%).
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 Gaelic influx, the period of Anglo-Saxon influx, the Viking era, the Norman invasion of 1066 and the era of the European wars of religion. There are also many potential eras of movement between different parts of the British Isles.
- 1 Analyses of nuclear DNA from ancient populations
- 2 Early studies of protein polymorphisms in modern populations
- 3 Y chromosomes and mitochondrial DNA from modern populations
- 4 Mitochondrial DNA
- 5 See also
- 6 References
- 7 Further reading
Analyses of nuclear DNA from ancient populations
Mesolithic Britons were closely related to other Mesolithic people throughout Western Europe. This population probably had blue eyes, lactose intolerance, dark curly or wavy hair, and, less certainly, dark to very dark skin..
Near-total population replacement by Neolithic farmers
Mesolithic Britons were closely related to other Mesolithic people throughout Europe, but Neolithic individuals are close to Iberian and Central European Middle Neolithic populations, modelled as having about 75% ancestry from Anatolian farmers with the rest coming from Western hunter-gatherers (WHG) in continental Europe. Some British Neolithic individuals had slightly (about 10%) more WHG genes, suggesting that some members of the WHG population in Britain did pass on their genes. Neolithic individuals from Wales have no detectable local admixture of Western hunter-gatherer genes, those from South East England and Scotland show the highest admixture of WHG genes, and those from South-West and Central England are intermediate. This suggests that farming was brought to the British Isles by sea from the west, by a population that was, or became in succeeding generations, relatively large.
Early studies of protein polymorphisms in modern populations
Luigi Luca Cavalli-Sforza used polymorphisms from proteins found within human blood (such as the ABO blood groups, Rhesus blood antigens, HLA loci, immunoglobulins, G6PD isoenzymes, amongst others). 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.
Y chromosomes and mitochondrial DNA from modern populations
With the advent of DNA analysis, modern populations were sampled for mitochondrial DNA to study the female line of descent, and Y chromosome DNA to study male descent. As opposed to large scale sampling within the autosomal DNA, 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.
A 2010 DNA study published in PLOS Biology showed that Neolithic farmers from the Middle East had a significant impact on the Y-DNA of European males, the majority of whom have paternal lineage tracing back to Middle-Eastern farmers during the Neolithic expansion. In contrast, the mtDNA of European females show the majority having maternal lineage tracing back to earlier hunter-gatherers predating the Neolithic expansion.
In 2007 Bryan Sykes produced an analysis of 6,000 samples from the OGAP project in his book Blood of the Isles. 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 paternal Y chromosome DNA evidence Oppenheimer reviewed the Weale and Capelli studies and suggested that correlations of gene frequency mean nothing without a knowledge of the genetic prehistory of the regions in question. His criticism of these studies is that they generated models based on the historical evidence of Gildas and Procopius, and then selected methodologies to test against these populations. Weale's transect spotlights that Belgium is further west in the genetic map than North Walsham, Asbourne and Friesland. In Oppenheimer's view, this is evidence that the Belgae and other continental people – and hence continental genetic markers indistinguishable from those ascribed to Anglo-Saxons – arrived earlier and were already strong in the 5th century in particular regions or areas.
Oppenheimer, basing his research on the Weale and Capelli studies, maintains that none of the invasions since the Romans have had a significant impact on the gene pool of the British Isles, and that the inhabitants from prehistoric times belong to an Iberian genetic grouping. He says that most people in Britain and Ireland are genetically similar to the Basque people of northern Spain and southwestern France, from 90% in Wales to 66% in East Anglia. Oppenheimer suggests that the division between the West and the East of England is not due to the Anglo-Saxon invasion but originates with two main routes of genetic flow – one up the Atlantic coast, the other from neighbouring areas of Continental Europe – which occurred just after the Last Glacial Maximum. He reports works on linguistics by Forster and Toth which suggest that the Indo-European languages began to fragment some 10,000 years ago, at the end of the last Ice Age. He claims that the Celtic languages split from Indo-European far earlier than previously suspected, some 6000 years ago. He claims that the English language split from the other Germanic languages before the Roman period, and became the English that was spoken by the Belgae tribes of what is now southern and eastern England, northeastern France, and Belgium prior to their conquest by the Romans, and long before the arrival of the Anglo-Saxons.
Bryan Sykes, a former geneticist at Oxford University, came to fairly similar conclusions as Oppenheimer, which he set forth in his 2006 book called Blood of the Isles: Exploring the Genetic Roots of our Tribal History, published in the United States and Canada as Saxons, Vikings and Celts: The Genetic Roots of Britain and Ireland. By 2010 several major Y DNA studies presented more complete data, showing that nearly all of the Y DNA subclades in Britain arrived more recently through Celtic and Germanic migrations from Central and Northern Europe during the Bronze Age, with some of the Mesolithic ancestry (I-M253) arriving from Scandinavia.
In 2012, from a highly enlarged whole-genome mitochondrial database published, the authors concluded that the most archaic maternal 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. They argued that this population came from a contracted European population refugium on the Anatolian Plateau which spread to three refugia, Franco-Cantabria, the Italian Peninsula and the East European Plain. From these three areas the lineages would then have repopulated Europe.
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 mass Anglo-Saxon immigration from the European continent, affecting up to 100% of the male genepool in Central 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. There is also evidence to suggest that a continental contingent, of ultimate steppe origins, might have occupied Britain at even earlier dates, such as the discovery that ~90% of the Neolithic gene pool of early Bronze Age Britain was replaced by 1,200 BC by a population descended from the lower Rhine area.
A study into the Norwegian Viking ancestry of British people found that there is evidence of particular concentrations in certain areas; especially the North Sea islands of Shetland and Orkney, but also to a lesser extent 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.
In Ireland, population genetic studies, including surname studies, have been undertaken by a team under Dan Bradley. 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.
Since 2010, 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 neighbouring countries. This has not yet led to any new theories concerning migrations.
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.
Two new genetic studies have recently been published on the Irish both showing that there is a large Northwestern French component to the Irish (called Celtic in this study) and a West Norwegian admixture event timed to the Viking era.
In 2007, 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 popularised "clan names" of Sykes, and in some cases also of Oppenheimer:-
- Haplogroup H (mtDNA) Helena (Sykes), Helina (Oppenheimer)
- Haplogroup I (mtDNA) Isha
- Haplogroup J (mtDNA) Jasmine
- Haplogroup T (mtDNA) Tara
- Haplogroup V (mtDNA) Velda (Sykes), Vera (Oppenheimer)
- Haplogroup W (mtDNA) Wanda
- Haplogroup X (mtDNA) Xenia
- Haplogroup U (mtDNA) Europa (Oppenheimer)
...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 7,300 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 chromosome DNA
In 2007, Sykes produced an analysis of 6,000 samples from the OGAP project in his book Blood of the Isles. 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 popularise the concept by giving them "clan names". The following gives their normal scientific names.
- Haplogroup R1b (Y-DNA). Oisin (Sykes), Ruisko (Oppenheimer). Oppenheimer attempted to divide this in 16 clusters.
- 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
- Haplogroup R1a (Y-DNA). Sigurd (Sykes), Rostov (Oppenheimer)
- Haplogroup E1b1b (Y-DNA). Eshu (Sykes)
- Haplogroup J (Y-DNA). Re (Sykes)
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 Britain and Ireland 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; R1 is now the most common haplotype in Europe. The second most common R1b subclade in England is R1b-S21 ("Germanic"), which is most common in North Sea areas such as eastern England, the Netherlands and Denmark. Ireland is dominated by R1b-L21 ("Celtic"), which is also found in north western France, the north coast of Spain, and western Norway on continental Europe. But R1B L21 is also common and dominates certain parts of England more so than other lineages.
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. Looking at the three main clusters, according to Rootsi et al., with up-dated nomenclature according to ISOGG:-
- 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, with frequency as high in Eastern England as it is 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, 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. However, there is no conclusive evidence that it came with Vikings, and similarities could have arisen from similar pre-Viking settlement patterns. Current Scandinavians belong to a range of haplogroups.
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 found most often 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%.
Uncommon Y haplogroups
Geneticists have found that seven men with the surname Revis, which originates in Yorkshire, carry a genetic signature previously found only in people of West African origin. All of the men belonged to Haplogroup A1a (M31), a subclade of Haplogroup A which geneticists believe originated in Eastern or Southern Africa. The men are not regarded as phenotypically African and there are no documents, anecdotal evidence or oral traditions suggesting that the Revis family has African ancestry. It has been conjectured that the presence of this haplogroup may date from the Roman era, when both Africans and Romans of African descent are known to have settled in Britain. According to Bryan Sykes, "although the Romans ruled from AD 43 until 410, they left a tiny genetic footprint." The genetics of some visibly white (European) people in England suggests that they are "descended from north African, Middle Eastern and Roman clans".
Geneticists have shown that former American president Thomas Jefferson, who might have been of Welsh descent, along with two other British men of the 85 British men with the surname Jefferson, carry the rare Y chromosome marker T. This 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.
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- A study headed by Dr Bradley was published in the American Journal of Human Genetics. Geneticists find Celtic links to Spain and Portugal
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- Malmström et al. 2009
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