The multiple maternal legacy of the Late Iron Age group of Urville-Nacqueville (France, Normandy) documents a long-standing genetic contact zone in northwestern France

Abstract

The compilation of archaeological and genetic data for ancient European human groups has provided persuasive evidence for a complex series of migrations, population replacements and admixture until the Bronze Age. If the Bronze-to-Iron Age transition has been well documented archaeologically, ancient DNA (aDNA) remains rare for the latter period and does not precisely reflect the genetic diversity of European Celtic groups. In order to document the evolution of European communities, we analysed 45 individuals from the Late Iron Age (La Tène) Urville-Nacqueville necropolis in northwestern France, a region recognized as a major cultural contact zone between groups from both sides of the Channel. The characterization of 37 HVS-I mitochondrial sequences and 40 haplogroups provided the largest maternal gene pool yet recovered for the European Iron Age. First, descriptive analyses allowed us to demonstrate the presence of substantial amounts of steppe-related mitochondrial ancestry in the community, which is consistent with the expansion of Bell Beaker groups bearing an important steppe legacy in northwestern Europe at approximately 2500 BC. Second, maternal genetic affinities highlighted with Bronze Age groups from Great Britain and the Iberian Peninsula regions tends to support the idea that the continuous cultural exchanges documented archaeologically across the Channel and along the Atlantic coast (during and after the Bronze Age period) were accompanied by significant gene flow. Lastly, our results suggest a maternal genetic continuity between Bronze Age and Iron Age groups that would argue in favour of a cultural transition linked to progressive local economic changes rather than to a massive influx of allochthone groups. The palaeogenetic data gathered for the Urville-Nacqueville group constitute an important step in the biological characterization of European Iron age groups. Clearly, more numerous and diachronic aDNA data are needed to fully understand the complex relationship between the cultural and biological evolution of groups from the period.

Multi-scale archaeogenetic study of two French Iron Age communities: From internal social- to broad-scale population dynamics

“…This is notably the case for circular buildings, the use of lignite as a raw material for the manufacture of bracelets or the position of some buried adults, which evokes the one encountered among the Durotriges group (a contemporary group based in Dorset; Lefort et al, 2015). Obviously, the interpretation of the UN site as a place of human circulation and gene flow along the Channel and the Atlantic coast (as already discussed in Fischer et al, 2018), could explain the higher maternal diversity measured for the community.…”

“…A higher success rate of HVS-1 sequence recovery could be observed for UN individuals when compared to GLN individuals (UN: 82.7%; GLN:57.5%, statistically significant; p value = 0.00846). The excellent conservation of mitochondrial DNA has already been highlighted for the UN necropolis (Fischer et al, 2018) and could be explained by its location on the edge of the Channel foreshore.…”

“…All aDNA analyses were conducted on individuals recovered from burials (i.e., not cremated) and targeted 51 individuals distributed throughout the entire necropolis. The sample included all individuals published in Fischer et al (Fischer et al, 2018) plus 6 newly analysed individuals (S1 Table ). To obtain a clear picture of the genetic diversity of sub-groups corresponding to distinct necropolis sectors or funerary practices, we targeted individuals from both outside (N=19) and inside the enclosure (N=32), as well as several individuals from the same small 8 groups of burials.…”

“…Mitochondrial lineages reported for the UN site combined those already published in Fischer et al (2018) and updated (some SNP profiles and HVS-I sequences could be completed), plus those obtained on 6 newly analysed individuals. In the end, 42 mitochondrial haplogroups (determined through SNP analysis) could be characterized over 51 targeted individuals (80.7% success rate), and 43 complete and authenticated HVS-1 sequences (mtDNA haplotypes) could be obtained (82.7% success rate) (S1 and S4a Tables).…”

The Funerary Architecture of the La Tène Period in North-western Gaul and Southern Britain

“…The Channel Islands and the Cotentin Peninsula show links with southern Britain and north-western Gaul, as seen in the burials of Urville-Nacqueville, Manche, which expose similarities to both Gallic and British funerary practices: cremation for the adults, inhumations in a folded position within wooden coffins for the children. A recent study of mitochondrial DNA haplotypes of individuals from Urville-Nacqueville cemetery exposed a wide diversity in the origins of women (Fischer et al 2018). These analyses revealed genetic sharing between the sample of individuals from this Iron Age site and ancient populations of the Bell Beaker period and the Bronze Age, and also those contemporary from the north of France, Spain, Great Britain, and regions of the Baltic and Central Europe.…”