Historical Genetics of the Cotenin Peninsula

This project is being carried out by Dr Richard Jones and Dr Turi King, in partnership with Prof Pierre Bauduin. It is a collaboration between the University of Leicester (UK) and the Centre de Recherches Archéologiques et Historiques Anciennes et Médiévales UMP6273 (CNRS/UCBN), Université de Caen Basse-Normandie (France). It unites two significant research strands: at Leicester, ‘The Impact of Diaspora on the Making of Britain’ funded by the Leverhulme Trust; and in Caen, ‘Diasporas, identitiés et transfers culturels dans les mondes normands médiévaux’.

Themes and questions

The first millennium AD witnessed significant movements of people across and between continental Europe, Scandinavia, Britain and Ireland. These led to territorial reorganization, the creation of new polities, and in some places, the emergence of unified states, as well as a raft of social, economic, cultural, and linguistic developments. Many of these folk migrations and periods of colonization and settlement are attested in the historical record and some can be traced through the archaeological record. Important questions remain, however, regarding the scale and timing of these diaspora.

Genetics offers a new way of approaching these issues in a period when both the historical and archaeological records are at best fragmentary. This science has already begun to offer important insights that would otherwise be difficult to determine from the written and physical evidence alone. This has been made possible through the multiplication of detailed local studies of the genetic make-up of modern populations which reveal significant variations in genetic signatures at local and regional scale. Put together, these offer a chance to assess similarities and divergences at a pan-European scale and account for these through known or previously unrecognised historical processes.

Our project targeted Normandy, a region which lacked a major study of historical genetics, and which couldn't furnish comparative data to be examined alongside existing datasets from Brittany, Britain, Ireland, the Low Countries, Frisia, and Scandinavia. This gap in our knowledge was all the more critical given Normandy’s unique yet shared history with its neighbouring territories. In particular, the Scandinavian take-over and colonization of parts of the duchy during the ninth and tenth centuries is poorly understood. Although historically attested, archaeological evidence for Viking settlement has proven elusive. Yet in certain parts of Normandy, notably in Seine-Maritime (Haute-Normandie) and Manche (Basse-Normandie), place-names of Norse or Danish origin appear to point to large-scale settlement, a scenario also seemingly reflected in the number of Scandinavian surnames which have survived in these areas.

Genetics offers an alternative way to gauge not just the scale of Scandinavian colonization in Normandy, but potentially to elucidate – through comparison with other datasets – the processes by which this occurred: it is not known, for example, whether Scandinavian settlers came directly to Normandy from their homelands or whether they settled indirectly from the English Danelaw or other Viking territories around the Irish Sea.

While the focus of this survey of modern DNA targeted the period of Viking settlement in Normandy, and in the Cotentin Peninsula more precisely, the programme had the additional potential to address a whole range of other historical questions pertinent to the specific region and the wider history of early medieval Europe including the ‘Germanic’ contribution to the region’s genetics following the settlement of Germanic tribes in the fifth century; and given its brief political annexation and geographic proximity to Brittany, the ‘Celtic’ contribution in western Normandy. Together with its Gallo-Roman heritage, the Cotentin offers an almost unique opportunity to examine some of the most important diaspora of the first millennium AD which led to the making of modern France and Europe.

Sample strategy

This programme focused specifically on this formative phase in the creation of Normandy where it formed part of the Viking DNA project. Since the Early Middle Ages there has been population growth and movement which has acted to blur the genetic signal of this earlier period. Two methods have been successfully developed elsewhere (on the Wirral Peninsula in north-west England, in Yorkshire and in Ireland) to sample individuals who are more likely to have deeper ancestry in a given area.

The first of these is surname-based sampling. Heritable surnames have been present in France since the early eleventh century and therefore men bearing old surnames from the region have been asked to take part. Surnames containing elements which might betray Scandinavian heritage were of particualr interest, such as Anquetil, Dutot, Equilbec, Gonfray, Ingouf, Lanfry, Osouf, Osmont, Quetel, Tougis, Tostain, and Raoult and their many variants. ‘Non-Scandinavian’ surnames are of interest too, particularly those found in the historical record which exhibit a strong regional association with the Cotentin peninsula.

The second method is geographic-based sampling. We were keen to make contact with individuals whose four grandparents were born and lived within an 50 kilometre radius of their current abode. Such family stability in a particular geographic location, going back over three generations, has been shown in other studies to be an effective way of tracing DNA markers back across much greater expanses of time. In England, it is often very difficult to find individuals who meet this criteria. In France, by contrast, familial ties to a particular commune or group of neighbouring communes over several generations remains common.  For this project all our donors met this criteria.

Analysis

We took samples from approximately 100 men who fulfil one or both of the sampling criteria. Because surnames are paternally inherited, only men have been asked to take part. This is a methodological issue rather than a historical one: we are aware that women played a significant role in the Scandinavian diaspora. Over and above our interest in surnames, men carry both the Y-Chromosome (past from father to son) and mitochondrial DNA (passed from mother to both sons and daughters). Consequently sampling males permits the collection and analysis of these two dimensions of human DNA to be most efficiently achieved.

This study used a model established by the Wellcome Trust-funded People of the British Isles project to analyse the results. DNA was extracted from the saliva and whole genome SNP typing carried out using the Affymetrix Genome-Wide Human SNP array. Whole genome SNP typing allows us to ascertain the DNA sequence that an individual carries at around 1 million sites simultaneously across the genome and examine genetic variability in and between populations. This is a method which provides a powerful way of understanding genetic ancestry and has been used very successfully in studies of the population genetics of modern populations in Europe. The 'old Normandy' population data-set underwent population genetic analysis alongside British, Norwegian, Danish and other European datasets.

It is not possible to identify individuals who took part in the study from our published research.