c. 750–800
The Viking Age begins
Scandinavian maritime expansion develops across northern Europe. The societies involved are already interconnected through trade, migration and political relationships.
An investigation into Scandinavian ancestry, maritime migration and the genetic history of North Pembrokeshire — and what the evidence can, and cannot, tell us about Viking influence across the county.
Read the essay ↓Ask whether there is Viking DNA in Pembrokeshire and the instinctive answer is yes. The western coast of Wales stood directly on the maritime routes that connected Scandinavia with Ireland, the Irish Sea, the western coasts of Britain and the Atlantic. Vikings were active around the Irish Sea for centuries, and Pembrokeshire was not an isolated inland landscape but a peninsula surrounded by sea routes.
The harder question is what “Viking DNA” actually means. There is no single Viking gene, no Scandinavian marker that can be read from a modern person's DNA and labelled “Viking”, and no convincing scientific basis for saying that a particular percentage of people in North Pembrokeshire are descended from Vikings.
Modern population genetics tells a more interesting story. Scandinavian ancestry can sometimes be detected statistically by comparing modern populations with reference populations from Scandinavia. Ancient DNA can identify individuals who lived during the Viking Age and reveal their genetic relationships. Y-chromosome studies can investigate particular male lines, while mitochondrial DNA follows maternal lines. None of these methods, however, turns ancestry into a straightforward ethnic label.
This matters particularly in Pembrokeshire. The county has a distinctive historical geography. It lies at the western extremity of Wales, faces Ireland across the Irish Sea, contains Milford Haven — one of the finest natural harbours in Britain — and has a long history of movement between Britain and Ireland. North Pembrokeshire adds another dimension: the coast around Fishguard, Strumble Head, Newport and St Davids sits close to the maritime corridor leading north and south through the Irish Sea.
The evidence therefore needs to be assembled rather than reduced to a single DNA percentage. Archaeology tells us about objects, settlements and contacts. Historical sources tell us about raids, kingdoms and political relationships. Place-names preserve traces of language. Genetics reveals population relationships. Together, these sources allow us to ask a much more sophisticated question:
Not simply whether Vikings reached Pembrokeshire, but whether Scandinavian people became part of the population of the region — and if so, how much of that ancestry survives today.
One of the most important developments in Viking-Age research has been the realisation that the word “Viking” should not be treated as synonymous with “Scandinavian”. Viking activity involved people from many backgrounds, and Scandinavian populations themselves were genetically diverse.
The large ancient-DNA study published in Nature in 2020 analysed the genomes of more than 400 individuals associated with the Viking world. It demonstrated substantial genetic diversity within Scandinavia and found that Viking-age people were not genetically identical to modern Scandinavians.
The study also showed that individuals associated with Viking activity could have substantial ancestry from outside Scandinavia. In other words, Viking identity could be cultural, political, social or occupational as well as genealogical.
This is especially important when looking at the Irish Sea. A Scandinavian settler arriving in west Wales might have been born in Norway, Denmark, Ireland, the Isle of Man, western Scotland or another part of the Viking world. His children might have had a Scandinavian father and a local Welsh or Irish mother. Their descendants might then have married into local communities for generations.
After several centuries, a population can retain genetic traces of an earlier migration without retaining a recognisably Scandinavian culture.
Consequently, “Viking DNA” is best understood here as shorthand for ancestry ultimately associated with Scandinavian populations during the Viking Age. It is not evidence that a modern Pembrokeshire family is culturally or ethnically “Viking”.
Geography does not prove genetic ancestry. But geography determines opportunity — and Pembrokeshire occupied an important position within the western maritime world.
The Viking Age was fundamentally maritime. Norway, the Northern Isles, the Hebrides, Ireland, the Isle of Man, western Scotland, north Wales and the Bristol Channel were connected by sea much more efficiently than their modern road maps suggest.
From a Scandinavian perspective, west Wales was not necessarily a remote corner of Europe. It was part of an interconnected Irish Sea zone in which merchants, settlers, raiders, slaves, pilgrims and political refugees could move between coastal communities.
The strongest case for Viking influence in North Pembrokeshire begins with its position on the Irish Sea, rather than with a single archaeological discovery.
North Pembrokeshire occupies a fascinating position in the history of the Irish Sea. The coast is close to Ireland, exposed to Atlantic traffic and divided into a series of natural harbours, bays and landing places. Modern infrastructure can make the landscape seem peripheral, but medieval maritime geography worked differently.
Fishguard is particularly significant in any discussion of maritime movement. Its harbour and coastal position place it within the wider network of western sea routes. St Davids, meanwhile, was one of the most important ecclesiastical centres in medieval Wales. Pilgrimage created movement across the Irish Sea, and religious traffic existed alongside commercial and political movement.
Yet there is an important distinction between “Vikings could have arrived here” and “Vikings settled here in large numbers”. The first proposition is historically very plausible. The second requires direct evidence.
The absence of a dramatic Viking settlement does not mean that Scandinavian people never reached Pembrokeshire. Conversely, the existence of Viking activity in the Irish Sea does not prove that a large Scandinavian population settled in North Pembrokeshire.
This distinction is at the centre of the genetic question. DNA can survive after cultural evidence has disappeared, but genetic evidence itself must be sampled and analysed. At present, the available population-genetic literature is much stronger for some other parts of Britain than it is for Pembrokeshire itself.
North Pembrokeshire therefore represents an excellent research problem rather than a solved case. The region's geography makes contact plausible; its position within the Irish Sea makes contact historically credible; but the modern scientific literature does not justify assigning the population a neat Scandinavian ancestry percentage.
“How much Scandinavian ancestry survived after the Viking Age had ceased to be a living culture?”
This is a population-history question, not a test of whether individual people are “really Viking”.
When trying to understand possible Scandinavian ancestry in Pembrokeshire, it is tempting to imagine a direct route from Norway to Wales. Historically, however, the story is likely to have been much more complicated.
The Irish Sea became a major Scandinavian sphere of activity from the ninth century onwards. Dublin emerged as a major Viking settlement and political centre. Scandinavian communities developed elsewhere in Ireland, the Isle of Man and western Britain.
People moved between these communities. Some were settlers; others were traders, soldiers, slaves, craftsmen or political migrants. A Scandinavian person living in Ireland could therefore become an ancestor of someone in Wales without ever travelling directly from Scandinavia to Wales.
This makes the phrase “Norse DNA” more useful than a simplistic idea of “Viking blood”. A Scandinavian genetic contribution could have passed through several generations and several locations before entering a Welsh population.
The Irish Sea should therefore be thought of as a population corridor. Pembrokeshire was one of its western-facing gateways.
That does not prove that North Pembrokeshire received a large Scandinavian settlement. It does, however, provide a historically credible mechanism through which Scandinavian ancestry could have reached the county.
Scandinavian maritime expansion develops across northern Europe. The societies involved are already interconnected through trade, migration and political relationships.
Scandinavian raiding and settlement expand through Ireland, the Isle of Man, western Britain and surrounding waters. The western coasts of Britain become part of a much larger maritime system.
Scandinavian political and commercial networks in Ireland create additional routes through which people can move between Ireland, Britain and the wider North Atlantic.
Scandinavian communities become increasingly integrated with local populations. The genetic consequences of migration therefore begin to differ from the cultural image of Viking warriors.
Even after Viking political activity declines, descendants of Scandinavian migrants can remain within local populations. Their ancestry may survive long after Scandinavian language and customs have disappeared.
Genome sequencing allows researchers to compare ancient individuals with modern populations and investigate migration at a resolution unavailable to earlier historians.
One of the most important studies of British population history is the People of the British Isles project. Using genome-wide data from geographically restricted British samples, researchers identified remarkably fine-scale population structure.
The results showed that Welsh populations occupy a distinctive genetic position. In the study's modelling, Welsh clusters generally had less ancestry assigned to putative Viking or Anglo-Saxon sources than many populations elsewhere in Britain.
This is an important result because it argues against an exaggerated picture of Viking genetic replacement in Wales.
At the same time, it does not mean that Welsh people have no Scandinavian ancestry. Population genetics works with distributions, probabilities and reference populations. Small amounts of ancestry can be present without producing a dramatic regional signature.
Later work has also shown that the genetic legacy of Viking expansion was highly uneven. The strongest Norwegian-associated signals occur in regions with especially intense Norse settlement, such as Orkney and Shetland.
The lesson for Pembrokeshire is therefore one of scale: the county should not be expected to resemble a heavily Norse-settled region simply because it was exposed to Viking activity.
This is a historically plausible pathway, not a proven genealogical chain for the people of modern Pembrokeshire.
If Scandinavian settlers did contribute to the ancestry of people in Pembrokeshire, the genetic signal would probably not look like a simple block of Scandinavian DNA. Population histories are layered. A small number of migrants can have descendants who become widespread, while a much larger settlement can leave surprisingly little genetic evidence if later population movements dilute the signal.
Imagine a Scandinavian man arriving somewhere in the Irish Sea region around the tenth century. He may have settled in a community where Welsh, Irish, Norse and other people already lived. If he had children with a local woman, his descendants would inherit approximately half of his autosomal DNA in the first generation. But that proportion would be progressively diluted as descendants married into other populations.
After ten or twenty generations, descendants might retain only small fragments of the original Scandinavian ancestry. Some descendants would inherit none of those particular fragments at all. Others could inherit more. The same ancestor could therefore be genealogically significant without leaving a dramatic autosomal signature in every branch of a family.
The situation is even more complicated because Viking-Age migration was not necessarily one-directional. People moved between Scandinavia, Britain and Ireland. Some communities were already genetically mixed before they reached Wales. The Scandinavian component in a modern Pembrokeshire genome might therefore represent an ancient Norwegian-associated lineage, but it could also have arrived indirectly through an Irish, Manx, Scottish or northern English population.
Autosomal DNA is the most useful broad measure of ancestry. It comes from both parents and is reshuffled every generation. Genome-wide studies can compare thousands or millions of variants and identify patterns of shared ancestry between populations.
This is the kind of evidence behind modern estimates of Scandinavian ancestry in Britain. The major ancient-DNA research published in Nature in 2020 provided an enormous new reference dataset for understanding Viking-age populations and their movements.
Such studies demonstrate that Viking migration had measurable demographic consequences in Britain. But they also show that those consequences varied enormously from one region to another.
The Y chromosome offers another window because it is passed largely from father to son. This means that particular male lineages can sometimes be traced over many generations.
Researchers have investigated Y-chromosome lineages associated with Scandinavian populations, including branches of haplogroup R1a. A study published in the European Journal of Human Genetics examined hundreds of R1a1 Y chromosomes and found evidence that some western-European sub-lineages had histories compatible with dispersal associated with Viking movements.
Importantly, however, a Y-chromosome haplogroup is not itself a “Viking marker”. Haplogroups are much older than the Viking Age. A lineage found in Norway may also be found in Britain for reasons unrelated to Viking migration.
The same caution applies to a modern Pembrokeshire surname. A surname that sounds Scandinavian would not, by itself, prove Viking descent. Conversely, a family with a completely Welsh surname could contain Scandinavian ancestry that entered the family centuries before modern surnames became stable.
Mitochondrial DNA follows a different line: from mothers to their children, although only mothers normally transmit it onward. It can therefore preserve evidence of female migration.
This is particularly significant because popular discussions of Vikings often concentrate on male warriors. Genetic history suggests a more complicated picture. Women travelled too, and Viking communities could include people from populations outside Scandinavia.
A Scandinavian genetic contribution to Pembrokeshire could therefore have arrived through either male or female lines. Y-DNA alone would capture only a small fraction of the total ancestry.
Ancient DNA is perhaps the most exciting area for future Pembrokeshire research. Modern population genetics can identify patterns in living people, but it cannot always tell us exactly when an ancestry component entered a population.
Ancient genomes provide a temporal anchor. If human remains from a securely dated Viking-Age site in or near Pembrokeshire were sequenced, researchers could ask whether those individuals had Scandinavian, local Welsh, Irish or mixed ancestry.
An even more powerful study would compare such ancient individuals with modern people whose ancestry is concentrated in North Pembrokeshire. That could potentially establish whether a Viking-Age population contributed genetically to the later population.
At present, this is better described as an important research opportunity than as an established Pembrokeshire result.
Evidence must come before ancestry claims.
The most defensible conclusion is not that North Pembrokeshire is “Viking”, but that it occupied a maritime world in which Scandinavian migration was possible and historically significant.
There is strong evidence that Scandinavian populations affected the British Isles genetically. There is strong evidence for Norse settlement in parts of Britain and Ireland. There is strong evidence that the Irish Sea was a major zone of Viking activity.
There is considerably weaker evidence for a large, clearly identifiable Scandinavian population specifically in North Pembrokeshire.
No reliable percentage of modern North Pembrokeshire residents can currently be described as having “Viking DNA” on the basis of the published research located for this essay.
That statement should not be interpreted as evidence of absence. It means that the question has not been tested with the sort of geographically focused genomic study that would justify a numerical answer.
Genome-wide and ancient-DNA studies demonstrate that Viking-Age migration had measurable demographic effects in Britain and the wider North Atlantic world.
The archaeology and history of Ireland, the Isle of Man, western Britain and the North Atlantic make movement through the Irish Sea beyond serious doubt.
A dedicated modern and ancient genomic study would be required to provide a robust county-level or North-Pembrokeshire estimate.
The most useful way to understand Viking influence is not as a single invasion but as a network of connections stretching across the North Atlantic and Irish Sea.
Norway, Scotland, the Northern Isles, Ireland, the Isle of Man, Wales and England were linked by ships. People could move between these worlds repeatedly, carrying genes as well as languages, technologies, religious ideas, objects and political traditions.
North Pembrokeshire is particularly interesting because it sits at the intersection of several different population histories. It is unmistakably Welsh in its cultural and linguistic traditions, yet it faces a maritime world that historically connected Wales to Ireland and the North Atlantic.
Its geography also encourages us to think beyond modern political boundaries. A Viking-age traveller would not have recognised “Pembrokeshire” in the modern administrative sense. The relevant landscape was a collection of kingdoms, ecclesiastical territories, coastal settlements, islands and maritime routes.
The genetic population of the region was similarly not divided according to modern county lines. Any Scandinavian ancestry that entered the area may have spread across neighbouring communities. It may also have arrived from elsewhere in Britain or Ireland.
This is why a future study should not sample only people living immediately around Fishguard. A serious investigation would need a geographically broad sample covering North Pembrokeshire, St Davids, the Preseli region, the southern peninsula, the Milford Haven area and neighbouring Ceredigion and Carmarthenshire.
Ideally, the study would also include people with multiple generations of local ancestry. Modern mobility can obscure historical patterns. Someone born in Pembrokeshire today may have parents or grandparents from London, Liverpool, Ireland, Scotland or elsewhere in Wales.
Researchers would therefore need genealogical information alongside DNA data. This would not make the study a family history project. Rather, it would allow researchers to distinguish recent migration from older population structure.
Such research could potentially reveal whether North Pembrokeshire forms a genetic continuation of wider Welsh populations or whether its maritime position has left a measurable additional signal.
One possibility is that the Scandinavian contribution is extremely small. Another is that it is measurable but diluted. A third is that a particular male lineage has a stronger Scandinavian association than the population as a whole. All three scenarios are compatible with the broader history of Viking Britain.
The evidence available today does not allow us to choose confidently between them.
Pembrokeshire should not be described as a region of Viking genetic settlement on the basis of the evidence currently available.
What can be said with much greater confidence is that Pembrokeshire existed within a maritime world heavily transformed by Scandinavian expansion.
The Viking Age connected Scandinavia with Ireland, Scotland, the Isle of Man, England and Wales. The Irish Sea was not a barrier separating these societies. It was a route through which people moved.
North Pembrokeshire's position makes Scandinavian contact historically plausible. Fishguard, St Davids and the wider northern coastline belonged to a maritime environment in which travellers could arrive from Ireland or from communities influenced by the Norse world.
But plausibility is not the same as genetic measurement. The modern genetic evidence indicates that Welsh populations generally retain a distinctive genetic profile with comparatively limited Scandinavian influence when compared with the strongest Norse regions of Britain.
That finding is actually more interesting than the simplistic claim that “Pembrokeshire has Viking DNA”. It suggests that the history of the region may be one of contact and exchange without large-scale population replacement.
Vikings could have visited without settling in large numbers. Small numbers of settlers could have arrived without transforming the regional gene pool. Individual Scandinavian families could have integrated into Welsh communities and disappeared culturally while leaving descendants.
The genetic legacy of such people, if it exists in measurable quantities, would therefore be fragmented across thousands of modern family trees.
The most compelling next step would be a dedicated genomic study of western Wales. Modern DNA sampling could be combined with ancient DNA, archaeology, medieval history and genealogical reconstruction. Researchers could then compare North Pembrokeshire with South Pembrokeshire, Ceredigion, Carmarthenshire, north-west Wales, Ireland and known Norse populations.
Such a project could finally answer the question that broad British studies cannot answer:
Did the Viking Age leave a detectable Scandinavian genetic footprint in Pembrokeshire — and is that footprint strongest along the western coast?
Until that research is done, the responsible conclusion is neither “there were no Vikings here” nor “the people of Pembrokeshire are descended from Vikings”. The evidence sits between those extremes.
Pembrokeshire was part of the Viking world in the sense that its sea lanes, neighbouring populations and political history were connected to the Scandinavian expansion. Whether that connection became a substantial genetic inheritance is a question that remains open.
Margaryan et al., Nature (2020). One of the
largest ancient-DNA investigations of Viking-age
individuals, analysing more than 400 genomes and
examining migration and genetic diversity across the
Viking world.
Read the Nature paper →
Leslie et al. and related work on fine-scale genetic
structure across Britain. The research demonstrates
substantial regional genetic structure and provides
important evidence concerning Welsh populations and
putative Scandinavian ancestry.
Read the Genetics review and discussion →
A study of R1a1 sub-lineages examined 619 Y chromosomes,
including 163 from the British Isles, and investigated
lineages associated with Viking-era Scandinavian
dispersal.
Read the study →
Leslie et al. examined more than 2,500 British and Irish
individuals and found strong regional variation in
Norwegian ancestry, with the highest levels in the
Northern Isles and substantially lower levels elsewhere.
Read the study →
Goodacre et al. investigated Scandinavian ancestry in
the Wirral and West Lancashire using Y-chromosome and
population-genetic approaches. The study is useful as a
comparison because it demonstrates how Viking ancestry
can be investigated in a region with strong historical
evidence for Scandinavian settlement.
Read the study →
The BBC's Blood of the Vikings series explored
the genetic and archaeological legacy of Scandinavian
migration in Britain. The programme is useful historical
context for the public discussion of Viking DNA, although
it should not be treated as a modern scientific study
specifically measuring Viking ancestry in Pembrokeshire.
BBC Programme Index →
Research into Viking-Age populations in Norway provides
another reference point for understanding the genetic
diversity of Scandinavian populations before and during
the period of expansion.
Read the research →