Gauls: variations mobility

[MOESAN]

a new survey:
Journal Pre-proof
Origin and mobility of Iron Age Gaulish groups in present-day France revealed
through archaeogenomics
Fischer Claire-Elise, Pemonge Marie-Hélène, Ducoussau Isaure, Arzelier Ana,
Rivollat Maïté, Santos Frederic, Barrand Emam Hélène, Bertaud Alexandre, Beylier
Alexandre, Ciesielski Elsa, Dedet Bernard, Desenne Sophie, Duday Henri, Chenal
Fanny, Gailledrat Eric, Goepfert Sébastien, Gorgé Olivier, Gorgues Alexis, Kuhnle
Gertrud, Lambach François, Lefort Anthony, Mauduit Amandine, Maziere Florent,
Oudry Sophie, Paresys Cécile, Pinard Estelle, Plouin Suzanne, Richard Isabelle,
Roth-Zehner Muriel, Roure Réjane, Thevenet Corinne, Thomas Yohann, Rottier
Stéphane, Deguilloux Marie-France, Pruvost Mélanie

[MOESAN]

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Origin and mobility of Iron Age Gaulish groups in present-day France revealed through1
archaeogenomics2
3
4
Fischer Claire-Elise*1,2, Pemonge Marie-Hélène2, Ducoussau Isaure2, Arzelier Ana2, Rivollat5
Maïté2,3,SantosFrederic2,BarrandEmamHélène4,5,BertaudAlexandre6,Beylier6
Alexandre7,8, Ciesielski Elsa8, Dedet Bernard8,Desenne Sophie9,10,Duday Henri2, Chenal7
Fanny5,9, Gailledrat Eric8, Goepfert Sébastien4,5, Gorgé Olivier11, GorguesAlexis6, Kuhnle8
Gertrud12, Lambach François2, Lefort Anthony9, Mauduit Amandine4, Maziere Florent8,9,9
Oudry Sophie9,13, Paresys Cécile9,14, Pinard Estelle9,10, Plouin Suzanne5, Richard Isabelle9,14,10
Roth-Zehner Muriel5,15, Roure Réjane8, Thevenet Corinne9,10,Thomas Yohann5,9, Rottier11
Stéphane2, Deguilloux Marie-France*2,16and Pruvost Mélanie*2,16,+
12
13
14
15
Summary16
The Iron Age period occupies an important place in French history,as the Gaulsare17
regularly presented as the direct ancestors of the extant French population. Wedocumented18
herethe genomic diversity ofIron Agecommunities originating from six French regions. The19
49acquired genomes permitted us to highlightan absence ofdiscontinuity between Bronze20
Age and Iron Age groups in France, lending support to a cultural transition linked to21
progressive local economic changes rather than to a massive influx of allochthone groups.22
Genomic analyses revealed strong genetic homogeneity amongthe regional groups associated23
with distinct archaeological cultures. This genomic homogenisation appearsto belinked to24
+Lead contact
*Correspondingauthors:claire-[email protected];marie-[email protected]-bordeaux.fr;
[email protected]-bordeaux.fr
1present address: Department of Archaeology, University of York, King’s Manor Exhibition Square, York,
YO1 7EP, UK
2UMR 5199 PACEA, CNRS, Université de Bordeaux, 33615 Pessac, France
3Department of Archaeogenetics, Max Planck Institue forEvolutionary Anthropology, Deutscher Platz 6,
04103 Leipzig, Germany
4ANTEA-Archéologie, Habsheim, France
5UMR7044Archimède,CNRS UniversitédeStrasbourg etUniversitédeHaute-Alsace,Strasbourg et
Mulhouse, France
6UMR-5607 Ausonius, Université Bordeaux Montaigne, Maison de l’Archéologie, 8 Esplanade des Antilles
33607 Pessac, France
7Service Archéologie Sète agglopôle mediterranée, 34110, Frontignan, France
8UMR 5140-ASM, Université Paul Valéry Montpellier 3, CNRS, Ministère de la Culture, Inrap, F34000
Montpellier, France
9INRAP, Institut National de Recherche Archéologiques Préventives, 75685 Paris cedex14, France
10UMR 8215 Trajectoires, CNRS, Université Paris 1 Pantheon Sorbonne, 92023 Nanterre, France
11Institut de Recherche Biomédicaledes Armées, Place Général Valérie André, 91220 Brétigny-sur-Orge,
France
12Landesamt für Denkmalpflege im Regierungspräsidium Stuttgart Referat 84.2–Operative Archäologie
Dienstsitz Freiburg Günterstalstraße 67, 79100 Freiburg i. Br.
13UMR-7268 ADES, CNRS, Université Aix-Marseille, EFS, 13015 Marseille, France
14UMR 7264 CEPAM, CNRS Université Nice Sophia Antipolis, 06357 Nice cedex4, France
15Archéologie Alsace, 11 rue Champollion 67600 Sélestat, France
16These authors contributed equally to this work



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individuals’mobility between regions as well as gene flow with neighbouring groups from25
England and Spain.Thus, the resultsgloballysupport a common genomic legacy for theIron26
Agepopulationof modern-day Francethat could be linked to recurrent gene flow between27
culturally differentiated communities.28
Introduction29
30
TheFrenchIronAgeholdsanimportantplaceinFrenchhistory,asGaulish31
communities are regularly presented to the general public as the direct ancestors of French32
populations. This major interest has led to an impressive number of archaeological studies33
describing Iron Age communities through their material culture andfunerary practices and34
questioning their cultural origins and affinities. Despitethis interest, questions concerning the35
cultural and biological processes underlyingthe emergence and expansion ofIron Age36
cultures remainintenselydebated. Thus, the transition between the Bronze Age(BA)and the37
Iron Age(IA)wasfirst linked to the rapidshiftfrom bronze to iron technologies between38
Hallstatt B3 and Hallstatt C (approximately800 BC).However, this clear cut-offdoes not39
appear toreflect the regional archaeological realitythat there was agradualtransition to the40
useofironinsteadofarapidsubstitution(Verger,2015).Moreover,thecultural41
transformations associated with the transition span over two centuriesencompassingthe late42
Bronze Age and the first phase of the Iron Age and appear to have followed different rhythms43
that varied byregion(Verger, 2015). Debates also concern the modes of emergence of the44
Late Iron Age cultureLa Tène, associated with groups generallyreferred to as‘Celts’ and45
spread over a large part of Europe, spanning from Bohemia to the Atlantic(Roure, 2020).46
Thus, some authors propose an advent of this cultural entity in Central Europe and Bohemia47
before its expansion through the migration of groupsbringing cultural developments from the48
northern Alpine area to the rest of Europe (Kruta, 2000; Brun, 2017).Otherauthors propose a49
multiregionalorigin of theLa Tèneculture through the evolution of a mosaic of cultural50
complexes ('multipolar genesisin networks'; Milcent, 2006) connected by common markers51
such as art without implying major migration.According to this view,the‘Celts’wouldbe52
defined as a multitude of related people with different cultural practices(Lejars and Gruel,53
2015).54
The great amount of archaeological data available for Iron Age groups from the55
French territory strikingly contrasts with the near absence of genomic data for the human56
groups concerned. In the archaeology of death, as well as in the study of ancient humangroup57
dynamics, palaeogenetic analyses have led to considerable advances. From the Palaeolithic to58
theBronzeAgeperiods,ancientDNA(aDNA)studieshaveprovidedarguments59
complementary to the archaeological evidence to reconstruct the dynamics of the groups at60
the Europeanmacroregionalscale (seeLiuet al., 2021 for a recent review), as well as61
discussions onthe social functioning of communities at the local scale (documenting,for62
example,residencerulesorfiliationsystems;e.g.Mittniketal.,2019).Despitethe63
considerable increase in palaeogenomic analyses over the last decade,someterritories or64
periods remain poorly documented. In that respect,theFrench territory remainedneglected in65
palaeogenomic studies in Europe until the very recent publication of three studies targeting66
this key crossroad region in western Europe(Brunelet al., 2020; Rivollatet al., 2020;67
Seguin-Orlandoet al.,2021). Nevertheless, genetic and genomic data forIAperiod from68
French territory remain scarce,with mitochondrial data for 91 individuals and low-coverage69
genomes for 19 individuals(Fischeret al., 2018, 2019; Brunelet al., 2020).To date, the70
underrepresentationofIApopulationsinpalaeogenomicstudies,comparedwithprior71
periods, can be extended to the European scale, with a total of44 mitochondrial sequences72
3
from Germany, Spain and Italy(Knipperet al., 2014,Núñezet al., 2016,Serventiet al.,73
2018)and a total of 27 genomic data points from England(Martinianoet al., 2016; Schiffels74
et al., 2016), Bulgaria(Mathiesonet al., 2018), Croatia(Mathiesonet al., 2018), Spain75
(Olaldeet al., 2019), Hungary(Gambaet al., 2014), Montenegro(Allentoftet al., 2015),76
Estonia(Saaget al., 2019)and Germany(Furtwängleret al., 2020).77
Theseobservationsareparticularlyfrustratinggiventhatonlytheacquisitionof78
representative palaeogenomic data for French Iron Age groups and their comparison with79
archaeological data can allowto directly characterise the biological processes potentially80
involved in the cultural transformations documented betweentheBronze Age and Iron Age81
orbetween the Early and the LateIron Age periods. Furthermore, compellinggenomic data82
for these ancient communitiesprovidethe only way to test for correlation betweenthe83
cultural and biological diversitiesof groupsand question modes of exchanges between84
populations. Finally, genomic data obtained at the local scale can provide major insightsinto85
the social organisation of communities. For older periods, whethertheNeolithic or Bronze86
Age, palaeogenomic studies have revealed recurrent patrilocal residence rules, patrilineal87
filiation systems or differences in social level(see,for example,Lacanet al., 2011; Mittniket88
al., 2019). For the Iron Age, the indirect testimonies left by Greeks and Romans (suchasDe89
Bello Gallicofrom Julius Caesar, even if they must be considered with caution) mentioned a90
very hierarchical society characterised by a patrilineal system of filiation. Thus, obtaining91
genomic data for the Iron Age communitiesrepresentsa unique opportunity to compare92
biological, archaeological and textual data.93
The outstanding questionspresentedabove and the great potential of the combination94
of archaeological, textual and genomic datain an attempt toresolvethem motivated us to95
better document the genomic diversity of the Gaulish populations. For this purpose, we96
targeted 145individualsfrom 27 sitesspread over the extant French territory and distributed97
throughout theIAperiod to optimise our chanceof documentingthe gene pool of a98
representative set of French Iron Age individuals. Thewidechronological distribution of the99
dataset permitted us to addressquestions of origin and evolution of the groups, whereas the100
wide geographical distribution of the samplesallowedus to test forinterregionalgene flow.101
Notably, some archaeological evidence highlighted particularexchangenetworks with the102
groups fromthesurrounding areas, such as the example of the necropolis of Urville-103
Nacqueville,sharing clear archaeological features (roundhouses, Durotrigian burials,etc.)104
with contemporaneous groups from Britain(Lefortet al., 2015).Finally, wealso targeted105
sites associated with different funerary practices to better understand the biological identity106
and potential selection of the individuals buried.

[MOESAN]

The Iron Age genomic dataset from France111
112
A total of 145individuals were targeted for palaeogenomic analyses(TableS1). DNA113
was extracted, andDNA libraries were built with a partial uracil-DNA glycosylase treatment,114
allowing for the assessment ofpostmortemdeamination patterns (2% to 29%) expected for115
ancient DNA data. Initial screening via shotgun sequencing of 1 to 2 million reads was used116
to select libraries with an amount of endogenous DNA above 15%, leading to the exclusion117
of 92individuals. For the remaining individualswhopassed these quality criteria, we118
sequenced the libraries to an average depth of 0.178X(Table S2). Wefound overall119
negligiblelevel ofcontaminationin our datasetby testing for heterozygosity of polymorphic120
sites on the X chromosome in males (TableS3). The dataset resulting from these successive121Journal Pre-proof
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quality selections encompasses low-coverage genomes for 49 individuals originating from 27122
sites,datingfrom the BronzeAge (N= 2) and the Iron Age periods (N=47).We compiled123
theIAdata with 18 low-coverage genomes already published forIAgroups from France124
(Brunelet al., 2020),leading to a total of 65 low-coverage genomes distributed in 6125
geographical areas: Alsace (N=20), Champagne (N=5), Normandy (N=3), North (N=126
10), South (N=18) and ParisBasin (N=9)(see Figure1A,STAR Methods andTables S1127
andS3). TheIAdataset isunbalanced in terms of the chronological distribution of the128
individuals, with 11 individuals dated to the Early Iron Age and 54 dated to the Late Iron Age129
period(Figure1B). This can be partly explained by the funerary treatment and the use of130
cremation (see,for example,Dedet, 2004 forsouthernFrance).The fewhumansremains131
(fromsouthern ornorth-westernFrance) available for genomic analyses represent deceased132
who escaped cremation and benefited fromnon-ordinaryfunerary practices.Therefore, the133
corpus available for genomic analysismaynotberepresentative of the entire population134
living at the time.For instance, forsouthernFrance, genetically analysedindividuals135
correspond to severed heads (seeSTAR Methods. site of Le Cailar) or toneonatesburied in136
settlements(seeSTAR Methods. site Le Plan de la Tour). The dataset is also unbalanced in137
termsof regional representativeness,with the Normandy region providing the lowest number138
of genomes due to the low DNA conservation in the coastal Urville-Nacqueville necropolis139
targeted(Table S1). Finally, among the 65 individuals, if 33weremales and 32werefemales,140
the sex ratio within each regionwasunbalanced, with notably more females in Alsace and141
more males in the South (Table S2). Withthis framein mind, we analysed our data with142
published ancientindividuals(n = 5225)genotyped on the 1240k panel(Mathiesonet al.,143
2015)as well withmodern (n = 6461) individuals from a panel of modern-day worldwide144
populations genotyped on the Affymetrix Human Origins (HO) panel.From thepresent145
study’sdataset,65individuals with more than 20,000 SNPs on the 1240k panel were used for146
the downstream genome-wide analyses (see STAR Methods andTable S2).Wefound no147
first-degree relatives among IA individuals from present-day France allowing us to keep the148
full datasetfordownstream analyses (see STAR Methods, Table S3and Figure S4).149
150
We first explored our data qualitatively usingprincipal component analysis (PCA)by151
projecting the ancient genomes onto the genetic variation ofanHO set of west Eurasians152
(Figure 1C andS1). French IA individuals fall within the genomic variability ofthemodern-153
dayFrenchpopulation. IA samples from Spain and Great Britain also fall within modern-day154
populations from the same region, highlighting a certain degree of continuity from the Iron155
Age to modern-day populations inwesternEurope, confirming previous results based on156
mitochondrial DNA(Fischeret al., 2018). The PCA alsoshowsa clinal distribution of our IA157
French samples according to their latitudinal position:the northernsamples arecloser to the158
extantGreatBritain population,and thesouthern samples are closerto the Spanishpopulation159
(FigureS1). These observations are fully consistent with genomic studies conducted on160
modern Europeans andhighlightageographically and genomicintermediate positionof the161
Frenchgroupsbetweennorth-westernandsouth-westernEuropeanpopulations(Novembreet162
al., 2008).163
164
165
To test further the genomic variability of thenewIA genomes, wegrouped the166
individuals among differentchrono-culturalgroups,i.e.,according to their region of origin167
and, when possible, to theirdating(Earlyvs.Late Iron Age):EIA_Alsace (from 800 BC to168
450 BC),LIA_Alsace (from 450 BC to 50 BC), IA_Champagne, IA_Normandy, IA_North,169
IA_Paris_Basin and IA_South. We then carriedoutaqpWaveanalysis iterated over all170
individuals in the pool, testing for significant evidence of heterogeneity relative to the171

5
remaining chrono-cultural group (seeSTAR Methods and Figure 2). Individuals were172
considered genomic outliersfrom the chronological-cultural group from which they originate173
when theqpWavep value was <0.05(Fernandeset al., 2020). This resulted in the174
identification of six individuals as outliers: BES1248, PECH3 and PEY163 stand as outliers175
fromtheIA_Southgroup,CROI11fromtheEIA_Alsacegroup,COL239fromthe176
LIA_Alsacegroup and GDF1341 from theIA_Paris_Basin group. The analyses at the177
regional level were consequently conducted separately on these individuals and their chrono-178
cultural groups. Theoutlier status of these special individuals will be further discussed.179
18

[Angela]

I just this minute finished reading it. There are so many caveats, starting with low coverage genomes and the lack of balance in terms of numbers between the early and late Iron Age that I have some hesitancy in accepting it.

"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."

https://www.cell.com/action/showPdf?pii=S2589-0042%2822%2900364-9

In my case, thanks to Lazaridis for the heads up.

[MOESAN]

Yes, too small samples and personally I'm not sure of the close cultural assignation of the southern France pop's of the time. "Gaul" in some way, but "Celt"? What seems sure independently of this survey is that internal moves occurred in Gaul during Iron and modified the most western parts of the territory. THis survey seems looking at things from far and high.