Genetic History of the British Isles

Figure 3
Major events in the peopling of the British Isles

To facilitate further discussion, Figure 3 and Extended Data Figure 8 give an overview of the major population groups and movements of people within and into the UK at different times, based on archaeological, historical and linguistic evidence. For more detail see the Supplementary Note.

Our observation that samples in Orkney differ genetically from those in the rest of the UK has been noted before18–21 and is consistent with the historical settlement, and long-term control, of Orkney by Norse Vikings (Orkney was a part of Norway from 875 to 1472). Further, the estimated ancestry profiles of the Orkney clusters show substantial contributions from groups in Norway (Fig. 2). This consistency with history and archaeology provides external validation of our approach.



The observation (Fig. 2, Supplementary Table 4) that particular European groups (e.g. GER3, FRA12, FRA17) contribute substantially to the ancestry profiles of some, but not all, UK clusters strongly suggests that at least some of the structure we observe in the UK results from differential input of DNA to different parts of the UK: the absence in particular UK clusters of ancestry from specific European groups is best explained by the DNA from those European groups never reaching those UK clusters. A critical observation which follows is that groups which contribute significantly to the ancestry profiles of all UK clusters most probably represent, at least in part, migration events into the UK that are relatively old, since their DNA had time to spread throughout the UK. Conversely, groups that contribute to the ancestry profiles of only some UK groups most probably represent more recent migration events, with the resulting DNA not yet spread throughout the UK by internal migration. “Old” and “recent” here are relative terms – we can infer the order of some events in this way but not their absolute times. Although we refer to “migration events” we cannot distinguish between movements of reasonable numbers of people over a short time or on-going movements of smaller numbers over longer periods.

After the Saxon migrations, the language, place names, cereal crops, and pottery styles all changed from that of the existing (Romano-British) population to those of the Saxon migrants. There has been ongoing historical and archaeological controversy about the extent to which the Saxons replaced the existing Romano-British populations. Earlier genetic analyses, based on limited samples and specific loci, gave conflicting results. With genome-wide data we can resolve this debate. Two separate analyses (ancestry profiles and GLOBETROTTER) show clear evidence in modern England of the Saxon migration, but each limits the proportion of Saxon ancestry, clearly excluding the possibility of long-term Saxon replacement. We estimate the proportion of Saxon ancestry in C./S England as very likely to be under 50%, and most likely in the range 10%-40%.



A more general conclusion of our analyses is that while many of the historical migration events leave signals in our data, they have had a smaller effect on the genetic composition of UK populations than has sometimes been argued. In particular, we see no clear genetic evidence of the Danish Viking occupation and control of a large part of England, either in separate UK clusters in that region (cf. Orkney), or in estimated ancestry profiles, suggesting a relatively limited input of DNA from the Danish Vikings and subsequent mixing with nearby regions, and clear evidence for only a minority Norse contribution (about 25%) to the current Orkney population.

We saw no evidence of a general “Celtic” population in non-Saxon parts of the UK. Instead there were many distinct genetic clusters in these regions, some amongst the most different in our analyses. Further, the ancestry profile of Cornwall (perhaps expected to resemble other “Celtic” clusters) is quite different from that of the Welsh clusters, and much closer to that of Devon, and Cent./ S England. Nevertheless, the data suggest that the Welsh clusters represent populations that are more similar to the early post-ice-age settlers of Britain than those from elsewhere in the UK.

Eur J Hum Genet. 2012 Feb; 20(2):203-10.

To facilitate further discussion, Figure 3 and Extended Data Figure 8 give an overview of the major population groups and movements of people within and into the UK at different times, based on archaeological, historical and linguistic evidence. For more detail see the Supplementary Note.


Figure 3
Major events in the peopling of the British Isles
See Supplementary Note for further details. a, The routes taken by the first settlers after the last ice age. b, Britain during the period of Roman rule. c, The regions of ancient British, Irish and Saxon control. d, The migrations of Norse and Danish Vikings. The main regions of Norse Viking (light brown) and Danish Viking (light blue) settlement are shown.

Our observation that samples in Orkney differ genetically from those in the rest of the UK has been noted before18–21 and is consistent with the historical settlement, and long-term control, of Orkney by Norse Vikings (Orkney was a part of Norway from 875 to 1472). Further, the estimated ancestry profiles of the Orkney clusters show substantial contributions from groups in Norway (Fig. 2). This consistency with history and archaeology provides external validation of our approach.

Our approach is clearly powered to detect quite subtle levels of population structure. Not finding such structure in central and southern England is thus informative. While some structure may exist within this region, there must have been sufficient movement of people, and hence of their DNA, since the last major invasions of the UK to make it relatively homogeneous genetically. This does not require large-scale population movements; it could be achieved by relatively local migration over many generations. This region of Britain lacks major geographical and (for the most part since the Roman occupation) geo-political barriers to human movement.



Other UK clusters may well reflect historical events. For example, several genetic clusters in Fig. 1 match the geo-political boundaries in Fig. 3c, and may represent remnants of communities/kingdoms present after the Saxon migrations, while the cluster spanning Northern Ireland and Southern Scotland may reflect the ‘Ulster Plantations’. The Supplementary Note contains further observations relating to the genetic clustering.

Relative isolation has clearly been a major determinant of fine-scale population structure within the UK. To assess the role of a different possible cause, namely differential migration into different parts of the UK, we estimated European “ancestry profiles” for each of the UK genetic clusters (Fig. 2). Here we must use modern-day groupings, in Europe and the UK, as surrogates for the sources and results of major migration events. Population movements between these events and the present, involving either the source populations or recipient groups, will attenuate signals of the original migration. For this and other reasons, it is hard to provide definitive explanations for our observations. Nonetheless, genetic differences persist through many generations and where we can check our conclusions against historical evidence, there is good concordance. In what follows we focus on the most likely explanations for various observations. See Supplementary Note for a fuller discussion. For definiteness, we focus on the clustering in Fig. 1 and Extended Data Fig. 6b, although other levels are informative. Analysis of additional UK and European samples, particularly in regions where our data is sparse (e.g. central Wales and Scotland, Spain, the Netherlands) would improve our ability to infer historical events.



After the Saxon migrations, the language, place names, cereal crops, and pottery styles all changed from that of the existing (Romano-British) population to those of the Saxon migrants. There has been ongoing historical and archaeological controversy about the extent to which the Saxons replaced the existing Romano-British populations. Earlier genetic analyses, based on limited samples and specific loci, gave conflicting results. With genome-wide data we can resolve this debate. Two separate analyses (ancestry profiles and GLOBETROTTER) show clear evidence in modern England of the Saxon migration, but each limits the proportion of Saxon ancestry, clearly excluding the possibility of long-term Saxon replacement. We estimate the proportion of Saxon ancestry in C./S England as very likely to be under 50%, and most likely in the range 10%-40%.

A more general conclusion of our analyses is that while many of the historical migration events leave signals in our data, they have had a smaller effect on the genetic composition of UK populations than has sometimes been argued. In particular, we see no clear genetic evidence of the Danish Viking occupation and control of a large part of England, either in separate UK clusters in that region (cf. Orkney), or in estimated ancestry profiles, suggesting a relatively limited input of DNA from the Danish Vikings and subsequent mixing with nearby regions, and clear evidence for only a minority Norse contribution (about 25%) to the current Orkney population.

We saw no evidence of a general “Celtic” population in non-Saxon parts of the UK. Instead there were many distinct genetic clusters in these regions, some amongst the most different in our analyses. Further, the ancestry profile of Cornwall (perhaps expected to resemble other “Celtic” clusters) is quite different from that of the Welsh clusters, and much closer to that of Devon, and Cent./ S England. Nevertheless, the data suggest that the Welsh clusters represent populations that are more similar to the early post-ice-age settlers of Britain than those from elsewhere in the UK.

In summary, we have presented the first fine-scale dissection of subtle levels of genetic differentiation within a country, by utilising careful sampling, genomic data, and powerful statistical methods. The resulting genetic clusters, and the characterisation of their ancestry in terms of European groups, provide important and novel insights into the peopling of the British Isles.

Nature. 2015 Mar 19; 519(7543): 309–314.