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Origin and mobility of Iron Age Gaulish groups in present-day France revealed through archaeogenomics
Fischer Claire-Elise et al.
https://www.cell.com/iscience/pdf/S...m/retrieve/pii/S2589004222003649?showall=true
Highlights
• 49 low coverage genomes from 27 sites from France, dated to ≈ 1200-80 years cal BCE
• No major migration or population turnover between Bronze and Iron Age in France
• A gradual North/South genetic structuration of IA populations
Summary
The Iron Age period occupies an important place in French history, as the Gauls are regularly presented as the direct ancestors of the extant French population. We documented here the genomic diversity of Iron Age communities originating from six French regions. The 49 acquired genomes permitted us to highlight an absence of discontinuity between Bronze Age and Iron Age groups in France, lending support to a cultural transition linked to progressive local economic changes rather than to a massive influx of allochthone groups. Genomic analyses revealed strong genetic homogeneity among the regional groups associated with distinct archaeological cultures. This genomic homogenisation appears to be linked to individuals’ mobility between regions as well as gene flow with neighbouring groups from England and Spain. Thus, the results globally support a common genomic legacy for the Iron Age population of modern-day France that could be linked to recurrent gene flow between culturally differentiated communities.
Genomic and cultural diversity among the Gauls
As previously mentioned, the PCA performed on the French IA dataset highlighted a clear latitudinal distribution of individuals (Figure 1C). The genetic differentiation projected on the PC2 axis is positively correlated with the latitudinal position of the sites where were found the samples in France (r²=0.59, Pearson). This correlation even increases when adding IA individuals from Iberian Peninsula and England (Figure 3C, r2254 =0.628). However, the f3 statistic applied in the form f3(Mbuti, Ind1, Ind2) showed no clear grouping of individuals in relation to their region of origin (Figure S5). To better characterise the genomic variability perceived between French IA individuals, we ran an f3 statistic in the form f3(Mbuti, X, Ind), where X represents an ancestral component (WHG, Anatolia_N and Russia_EMBA_Yamnaya). The results clearly pointed out differences between regions of France with a greater affinity between IA_South and the Anatolia_N component, whereas IA groups from northern French (notably Normandy) regions present more affinity with the Steppe-legacy component (Figure S6 and Table S6). To more precisely quantify these gradual affinities, we performed a qpAdm analysis modelling the IA French groups with these three components as source populations (Table S7). The modelling results clearly confirm that a decreasing north to south gradient in the steppe-related component among IA French groups is inversely correlated with an increase in the early farmer component (Figure 3A and S8). The scarcity of data from Bronze Age periods did not allow us to compare these differential affinities at a fine regional scale for this period, but it is worth noting that the distribution of available data into two separated groups, North vs. South, permitted us to observe the same tendency (Figure 3B and S7). This steppe-related ancestry gradient is well established for Journal Pre-proof 7 modern-day European populations (Haak et al., 2015) and appears to be well established in French territory, at least since the BA period.
