Sedgeford featured in major ancient DNA publication

Individuals from Sedgeford’s early medieval cemetery have contributed to a large ancient DNA (aDNA) study on migration, which has been published in the journal Nature [1].

The study used ancient genetic data to look at links between migration from continental Europe and (material) cultural transition in early medieval England, following the departure of the Romans in the 5th century CE. The cultural shift was traditionally attributed to invasions of elites from continental Europe, largely based on later historical accounts. However, this argument, as well as the nature of migrations from Europe into England at the time, has been widely debated. The Max Planck Institute for Evolutionary Anthropology sequenced DNA from archaeological skeletal remains from 479 individuals. These were all dated to between 200 and 1300 CE and from north-west Europe (England, Ireland, the Netherlands, Germany, and Denmark). The sequenced data were combined with existing contemporary data. These and modern genomic data were used to identify shifts in genetic ancestry, and therefore potential migrations.

The Sedgeford Historical and Archaeological Research Project (SHARP) was delighted to be part of such significant research. Bone or tooth samples were selected from individuals in SHARP’s archive of skeletons. SHARP’s sampling strategy took into account the aims of the migration study as well as questions specific to the Sedgeford site. This was done in consultation and collaboration with lead authors of the study; Joscha Gretzinger, Dr Stephan Schiffels, and Professor Duncan. The petrous portion of the temporal bone was sampled where a skull was already fragmented and molars were used when a selected skull was complete, to minimise unnecessary destructive sampling. Of the 22 samples submitted, DNA was successfully analysed for 20. This included individuals who were each discovered as an articulated burial from the early medieval cemetery and one contemporary skull which was excavated from a pit deposit within the cemetery boundaries, disarticulated by later human activity on the site (pit 9000). Also included in the analysis was a sample from an individual Iron Age crouched burial, found nearby to the location of the cemetery.

The study concludes that aDNA supports the hypothesis that the transition to the early medieval period in England was associated with migration from continental Europe. The results demonstrate that in early medieval England, there was an increase in genetic ancestry from the continental North Sea area (referred to as Continental North European, or CNE, ancestry). Early medieval English individuals analysed in the study had on average 76% CNE ancestry, although this was variable within and between cemeteries. The ancestries of individuals in medieval northern Germany and Denmark were statistically indistinguishable from contemporary English individuals, with populations from Lower Saxony and England being almost identical genetically. This suggests that the majority of the people who brought CNE ancestry to England came from Lower Saxony, although it is difficult to be precise due to homogeneity in contemporary genetic profiles across the continental North Sea and western Baltic. There were higher amounts of CNE ancestry in eastern England, suggesting that immigrants initially arrived in the east. All the sampled early medieval individuals from Sedgeford had over 95% CNE ancestry. Such high levels of CNE ancestry suggest that these individuals were either immigrants, or direct descendants of immigrants.

The study also shows that the migration of individuals from continental Europe into England took place over a longer period than previously assumed, into the Middle Anglo-Saxon period. Sedgeford, with an approximate date of 650 – 850 CE, has contributed significantly to this conclusion. The high levels of CNE ancestry at the Sedgeford site suggests that individuals with CNE ancestry were arriving as late as the 8th century in eastern England, coinciding with later Scandinavian mobility. The distribution of the ancestry results, including at lower status sites such as Sedgeford, shows that the migration happened across society, and did not only involve elites. Analysis of genetic markers linked to maternal and paternal lineages (mtDNA and Y-chromosomes) suggests that both males and females migrated to England and mixed with the local population in similar amounts. This shows that the early medieval migration was not male-dominated, in contrast to earlier migrations such as in the Beaker period [2].

Ancestry linked to Scandinavian and French Iron Age populations, was also identified. It is unclear how and when this ancestry was brought to Britain, although it appears that French Iron Age populations may have migrated to southern England. This is reinforced by the Frankish and Merovingian influences on material culture in the south of England in the early medieval period.

The definitive identification of genetic and biological sex for the Sedgeford sample of individuals has provided SHARP with an opportunity to review its estimations of sex made from osteological methods. In all cases where SHARP had estimated sex as either male, probable male, probable female, or female, this corresponded with the genetic data. The genetic data for several non-adult individuals, for which sex estimation by standard osteological methods is not possible, will prove extremely valuable to SHARP in its research plans for sex estimation of non-adults.

Another important result for SHARP was that the study also provides us with information about the genetic relationships between some of the individuals from Sedgeford. For a number of years, it has been suggested that three skeletons (S1016, S1018, and S1033) were victims of a single violent attack, based on palaeopathology, burial contexts and skeletal morphology. It is likely that two of these individuals, S1016 and S1018 were buried in the same grave cut. S1033 may have been buried slightly later, as the skeleton is placed at the foot of the burial of S1016. However, it is likely that this individual was buried at a similar time because the pattern of perimortem injuries closely matches those of S1016 and S1018, suggesting a single attack or closely linked series of attacks. The skeletal morphology of all three individuals is remarkably similar. All are males based on pelvic and cranial markers, as well as general robusticity and stature estimations. The morphological features of these individuals are also similar. This had led to the tentative suggestion that, based on osteological estimations, they may have been related [3]. Radiocarbon dates are also consistent with all three individuals having died at the same time.

These three individuals were selected to be part of the ancient DNA (aDNA) study in order to test the hypothesis of genetic relatedness amongst them. Not only has aDNA analysis corroborated the osteological sex assignment by showing that all three were male, but it has also shown that S1016 and S1018 were brothers, and that S1033 was the son of S1016. This was demonstrated using mtDNA haplogroups and LcMLkin. A further individual from the cemetery, found in Pit 9000, was determined to be a third-degree genetic relative (for example a maternal uncle or great-grandfather) of the brothers. Since he does not have the same Y-chromosome or mtDNA haplogroup, he is not a direct paternal line or maternal line ancestor of the trauma victims. This suggests a broader family tree, or ‘pedigree’, may be present in the cemetery population – the ancestry data, which shows little admixture with individuals without CNE ancestry, supports this. The hypothesis that many individuals in the cemetery were biologically related would be interesting to investigate with further aDNA analysis.

This study is significant because it both places Sedgeford in a key position in characterising the context of the cultural shift in early medieval England, and gives us a more intimate understanding of the lives and relationships of individuals buried at the cemetery. It is hoped that in the future, more skeletal individuals excavated from Boneyard and Reeddam can be included in aDNA analyses to extend our understandings of ancestry and genetic relatedness at the site. We are currently working towards this goal through further collaboration with Max Planck Institute for Evolutionary Anthropology. aDNA research is also providing further information about the lives of individuals buried at Sedgeford, beyond ancestry and relatedness. Research in collaboration with Dr Arthur Kocher has identified one of the individuals from Sedgeford as having suffered from Hepatitis B [4, 5]; SHARP is also part of an ongoing study that explores the presence of tick-borne pathogens within the early medieval population from Sedgeford.

Lucy Koster

Supervisor on the Human Remains Team at the Sedgeford Historical and Archaeological Research Project

PhD candidate at University of Aberdeen studying ‘Fragments of a Soul: integrating (and interrogating) aDNA and multi-isotope data to reconstruct the individual’

References:

[1] Gretzinger, J., et al. (in press). ‘The Anglo-Saxon migration and the formation of the Early English gene pool.’ Nature. In press.

[2] Armit, I., and Reich, D. (2021). ‘The return of the Beaker folk? Rethinking migration and population change in British prehistory.’ Antiquity 95(384):1464-1477 https://doi.org/10.15184/aqy.2021.129

[3] SHARP. (2014). Digging Sedgeford: A people’s archaeology. Suffolk: Poppyland Publishing.

[4] Salter, S. (2021). ‘SHARP contributes to study of ancient hepatitis’. SHARP Blog. 23 November 2021. [Blog]. Available at: https://www.sharp.org.uk/single-post/sharp-contributes-to-study-of-ancient-hepatitis

[5] Kocher, A., et al. (2021). ‘Ten millennia of hepatitis B virus evolution.’ Science 374(6564):182-188 https://doi.org/10.1126/science.abi5658