Population Genetics Of The British Isles

Map of Northwestern Europe, circa 10,000 BCE.

The genetic history of the British Isles is a very long one, with numerous groups of settlers leaving their mark on the area, some more so than others. Archaeological evidence suggests the first group of modern humans to settle in modern day Britain arrived approximately 11,500-12,000 years ago from continental Europe during the last ice age, when a land bridge known as “Doggerland” connected Britain and Ireland to the European mainland . However, earlier groups of pre Homo-Sapiens were likely in the area from around 800,000 years ago. The arrival of these early groups of settlers coincided with rapidly warming temperatures, as groups of hunter gatherers followed herds of reindeer and horses grazing the newly emerging grasslands, which formed as the ice retreated . The British isles have been continuously settled from this time period through to the present day.

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Waves of settlement

Farming groups, originating from the Anatolia region (Located in modern day Turkey) largely replaced this early group of settlers, with these Neolithic cultures first appearing in Great Britain around 6,000 years ago , with many also eventually making their way to Ireland, travelling across a land bridge from modern day western Scotland. Based on haplogroup analysis, it is likely that at least some of these settlers migrated from present day northern Spain, more specifically from areas in and around the Basque Country. These settlers also introduced farming into the isles. The resulting mix of Indigenous Western Hunter Gatherers and farming groups became what is known as the Early European Farmers (EEF). This megalithic culture was responsible for many of the ancient monuments found across the British isles, including Stonehenge.

However, between approximately 2,800-4,400 years ago, during the British Bronze Age, this group would themselves be largely replaced by further waves of migration from continental Europe, by a group known as the Bell Beakers. The beakers were themselves ethnically mixed, being a combination of Indo Europeans who migrated into Europe from the Pontic Caspian Steppe (Sometimes referred to as the “Yamnaya”[Russian for “pit grave”], although in practice the Indo Europeans were most likely a mixture of several different ethnic groups from this region) and local European hunter gatherer and farming groups, who they encountered during their migration west across the European continent, a journey which eventually led them into the British isles. The beakers were known for their distinctive pottery style, with the name beaker a reference to the types of pots made by these people , and they also introduced metalworking into the isles, including the use of copper and tin, which were subsequently used to make Bronze, leading to the gradual replacement of stone tools with metal ones over the following 1,000 years. Additionally, they are also believed to have introduced the horse into Britain, with their Steppe ancestors the first in the world to tame this animal. These Bronze Age settlers created a vast trade network which stretched across most of Europe, and several distinct beaker groups existed throughout the continent, with those settling in the British isles falling into the Western European beaker group. The presence of the beaker people in Western Europe also coincided with the disappearance of the megalithic peoples from these areas, with around 90% of the population living in the isles at this time replaced by the migrating beaker groups . Additionally, their arrival also coincides with the widespread introduction of the R1b paternal lineage into Western Europe, which today is the dominant male lineage in Western Europe, especially in the British isles, where it reaches its highest frequencies in modern day Ireland .

Source: https://www.haaretz.com/archaeology/2021-12-28/ty-article/genetic-study-detects-unknown-vast-migration-to-britain-3-000-years-ago/0000017f-e2ff-d568-ad7f-f3ff28960000

Within the British isles, the Bronze Age period saw a distinct ethnic makeup begin to take shape, with many small tribes emerging across the region. These new settlers were typically less pigmented then the previous EEF population, helping to explain the prevalence of lighter skin and eye colouring among the people who came to be known as the British and Irish. However, early in the first millennium BCE, considerable gene flow from mainland Western Europe, with genetic makeup most similar to individuals from present day France, was introduced into the isles, with these individuals likely originating from the continental (Alpined) Celts of central and western Europe who spread across the continent with the expansion of the Hallstatt civilisation, which originated in central Europe. Therefore, it was likely these groups who introduced Celtic culture into Britain, with the tribal groups which would go onto become the Celtic Britons in Britain and the Gaels in Ireland, would have been a hybrid of these settlers and the earlier Beaker population. This gene flow was significantly more prevalent in the southern part of Britain (England and Wales) compared to the north (Scotland), and in Ireland . These migrations also increased the amount of EEF ancestry in southern Europe compared to the north, and aligned with a broader trend of increased cultural exchange throughout central and western Europe during this middle to late Bronze Age period , while the bell beaker settlements from mainland Europe tended to come from further north and as such contained comparatively lower levels of EEF ancestry.

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Migration to the British Isles during the Iron and Roman Ages

Comparatively, the Iron Age - circa 800 BC—43 AD - was a period of relatively little migration to or from Britain. One possible reason for this was the abundance of iron ore, the use of which was widespread during this era, as opposed to the Bronze Age, where the supply of copper ore - required to make bronze - was far less abundant, facilitating the need for greater migration and trade . Eventually, this period of relative tranquility was eventually interrupted with the arrival of the Romans in AD 43, who successfully invaded the island, ruling in modern day England and Wales, and even extending into the southern region of Scotland. However, despite remaining in Britain for several centuries and leaving behind a significant cultural legacy, studies have concluded that their genetic contribution was minimal ; although more recent findings have posed some challenge to the current general academic consensus on this matter. For example, research from Schiffels and Durbin (2014) , in their analysis of several pre-Roman era Celtic Briton and medieval era Anglo-Saxon skeletons, found no traces of west Asian or east Mediterranean ancestry in the former and negligible amounts in the later, unlike modern British samples which possess small yet significant amounts of genetic ancestry from these regions, pointing towards possible Roman-era genetic input into Britain from the Mediterranean area.

By contrast, the subsequent waves of Anglo Saxon migrations from the north Germanic tribes known as the Angles, Saxons and Jutes (From modern day northern Germany and southern Denmark), left a strong genetic mark on the island, especially in the south eastern parts of Britain. This is in addition to a strong cultural legacy in the way of language, politics, and daily customs, with the modern nation of England often differentiated from its so-called Celtic neighbours of Ireland, Scotland and Wales on the basis of this strong connection to “Anglo-Saxon” culture. However, it is most likely the modern “English” nation in its earliest incarnation during the era of Alfred the Great (871-886 AD) was a blend of influences from the existing Romano-British society and the later Anglo-Saxon input, as most contemporary historians agree the Anglo-Saxon migration into Britain would’ve likely occurred in multiple waves over a period of centuries (the Anglo Saxon migration and the beginnings of the English). Furthermore, studies based on archeological and genetic evidence have shown some native Britons adopted Anglo-Saxon customs, further suggesting a pattern of continued integration rather than one large scale invasion.

DNA mapping Britain

Source: The Irish DNA Atlas, Gilbert et.al. 2017

This contention is supported by findings from the first large scale genetic study of the British Isles, the Oxford University commissioned “People of the British Isles” research project. The study, which collected DNA samples from 2039 participants, each with all four grandparents born in a particular region of the British Isles, showed many interesting patterns in DNA distribution across the isles, many of which align with the geographical boundaries of Britain dating back to the end of the 6th century, following the initial Anglo-Saxon settlements . The results showed several distinct genetic clusters, including ones for Wales; Northern Ireland/South-Western Scotland, and Eastern Scotland, while the majority of England also forms a distinct genetic cluster, most likely due to the greater blend of Celtic and Germanic DNA, compared to other areas of Britain which are more predominantly Celtic in their genetic makeup . However, these findings simultaneously challenge the notion of a unified “Celtic” nation. Even the small region of Cornwall in the south west corner of England showed distinct regional variations in DNA, due to the region’s long standing resistance to the Anglo-Saxon kingdom of Wessex, while neighbouring Devonshire, which was incorporated into Wessex later than other areas of England, was also genetically distinct, being a cross between their Cornish neighbours and the remainder of England. As for the genetic contribution of the Anglo-Saxons to the British gene pool, this was estimated to vary between 10-40%, and was highest in eastern England, which is where Anglo-Saxon settlement was heaviest. The study also suggests a limited genetic signature from the Danish Vikings who invaded and settled England intermittently between 793 and 1066 AD . However, due to the previous aforementioned settlement of the Danish-German Angles in the same regions of northern and eastern areas of England, the same areas later conquered by the Danish Vikings and subsequently incorporated into the “Danelaw” territory during the Viking age, it was not possible for researchers to clearly distinguish one group from another. Further, evidence based on haplogroup analysis investigating paternal (Y-DNA) lineages shows the Nordic paternal lineage I1 is present in between 15-20% of sampled males in most of eastern England, as well as southern Scotland, areas which were commonly subject to Viking raids, suggesting at least some of the heavy Danish genetic influence in England likely came about during this era .

Y-DNA has also helped researchers to paint a more detailed picture of the Anglo-Saxon influence on the genetics of the British. According to a study of 313 males from several towns across central England and northern Wales, when the Y-DNA haplotypes of those surveyed were compared with individuals from north-western continental Europe, between 50-100% of sampled males from central England shared haplotypes in common with the men from continental Europe, while the majority of Welsh males possessed haplotypes more commonly found predominantly in the British isles. These findings suggest a substantial migration of Anglo-Saxon Y chromosomes into Central England, which did not extend into North Wales, findings consistent with historical accounts. Furthermore, a 2022 study by Gretzinger et.al., point to a large genetic contribution from north Germanic groups into eastern England during the medieval period, with medieval individuals from this area deriving 76% of their ancestry, on average, from these continental European groups. Today, this figure is around 50% among individuals with long family histories in the area. Interestingly, the study also detected a significant contribution - up to 40% in areas of southern England - from groups with genetics most aligned with those of individuals from Iron Age northern France , which aligns with the findings of Patterson et al. discussed above, and corroborated by the People of the British isles study. However, the authors also hypothesise that this similarity could be, at least in part, a result of a genetic contribution from the Normans, a mixed Franco-Norse people who - led by William the Conqueror - successfully invaded England in 1066 , where they went on to form a ruling class which would last for centuries.

DNA mapping Ireland

Regarding the impacts of migration from continental Europe into Ireland, a similar study to the PoBI project, “The Irish DNA Atlas”, was conducted in 2017 . Their research used a combined dataset of 2,103 Irish and British individuals. The British individuals were sourced from the PoBI study, while the 536 selected Irish individuals were collected from multiple sources including the PoBI study, Trinity database, and directly from The Irish DNA Atlas project. From this large database, researchers were able to identify distinct genetic clusters within the island of Ireland, which generally align well with historical geographic boundaries. Seven of these are aligned with traditional Gaelic Irish populations, while three are indicative of mixed Irish-British ancestry . All three of the later make up the Northern Irish clusters, consistent with the region’s history of British occupation, beginning with the Ulster plantation in the 16th and 17th centuries, although it should be noted that there is a long history of people movements between this area and south western Scotland, with the Scots or Scoti having originated from this area, while the ancient Gallowglass civilisation also spanned areas of modern day Northern Ireland and western Scotland.

Another key finding of the study was a significant portion of Norwegian ancestry across all ten Irish clusters, which appeared in higher concentrations than in any of the British clusters, with the exception of those from the Orkney Islands, a former Norwegian settlement located in the North Sea . In most areas of Ireland, the average amount of Norwegian ancestry varied from around 10-15% , a finding consistent with Ireland’s documented history of Viking invasions and the establishment of Norse settlements across the island, with the city of Dublin at one point being a large Viking settlement and trading port. This is also another subtle distinction with the English whose history with the Vikings is more closely tied to the Danish Vikings, both historically and genetically. However, modern Ireland as a whole display a closer genetic affinity with continental Western Europeans, while the English are closely tied to modern day Scandinavians . The subtle differences between sampled English and Irish groups are probably due to a combination of factors including Ireland’s relative geographical isolation which gives it a more distinct genetic profile which still possesses strong components from ancient north western Europe, and England’s strong ties to other North Sea populations through historical migrations (i.e. Anglo-Saxons and Vikings), and trade. For example, the Irish DNA Atlas study also discovered strong genetic input into Ireland from modern day northwestern France and western Germany, with the latter explained by ancient Bell Beaker migrations, while the former is likely a combination of this and the genetic similarity between the Irish and the Breton people who live in modern day Brittany but are allegedly descended from native Britons who reportedly migrated into France following the Anglo-Saxon settlement of Britain. An additional potential factor could have been been the Norman occupation of Ireland from the 12th century, which in a country with a relatively small population, such as Ireland, would have had the potential to create some degree of genetic bottleneck.

The British isles today

In the modern era, this history of significant migration has continued, and since the 19th century, has encompassed groups from all across the world, including the oldest Chinese population in Europe, dating to the 19th century . Similarly, the “native” British population has itself been shaped by numerous migrations, forged through major historical developments, including changes in climate, technological advancements, political conflicts and changing economic circumstances.

See also

• English ethnicity
• Scottish ethnicity
• Irish ethnicity

Explore more about the Population genetics of the British Isles

• Scientists Are Mapping the DNA of Every Living Thing in the British Isles on the MyHeritage blog
• Perspectives on Combining Genealogy and Genetics webinar by Gilad Japhet at Legacy Family Tree Webinars
• Examining Migration & Researching Migrants in the British Isles webinar at Legacy Family Tree Webinars
• Challenges with Irish Genetic Genealogy webinar at Legacy Family Tree Webinars

References

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