Continental influx and pervasive matrilocality in Iron Age Britain

Abstract

Roman writers found the relative empowerment of Celtic women remarkable¹. In southern Britain, the Late Iron Age Durotriges tribe often buried women with substantial grave goods². Here we analyse 57 ancient genomes from Durotrigian burial sites and find an extended kin group centred around a single maternal lineage, with unrelated (presumably inward migrating) burials being predominantly male. Such a matrilocal pattern is undescribed in European prehistory, but when we compare mitochondrial haplotype variation among European archaeological sites spanning six millennia, British Iron Age cemeteries stand out as having marked reductions in diversity driven by the presence of dominant matrilines. Patterns of haplotype sharing reveal that British Iron Age populations form fine-grained geographical clusters with southern links extending across the channel to the continent. Indeed, whereas most of Britain shows majority genomic continuity from the Early Bronze Age to the Iron Age, this is markedly reduced in a southern coastal core region with persistent cross-channel cultural exchange³. This southern core has evidence of population influx in the Middle Bronze Age but also during the Iron Age. This is asynchronous with the rest of the island and points towards a staged, geographically granular absorption of continental influence, possibly including the acquisition of Celtic languages.

Full text

1136 | Nature | Vol 637 | 30 January 2025
Article
Continental influx and pervasive
matrilocality in Iron Age Britain
Lara M. Cassidy1 ✉, Miles Russell2, Martin Smith2, Gabrielle Delbarre2, Paul Cheetham2,
Harry Manley3, Valeria Mattiangeli1, Emily M. Breslin1, Iseult Jackson1, Maeve McCann1,
Harry Little1, Ciarán G. O’Connor1, Beth Heaslip1, Daniel Lawson4, Phillip Endicott5,6 ,7,8 &
Daniel G. Bradley1
Roman writers found the relative empowerment of Celtic women remarkable1.
In southern Britain, the Late Iron Age Durotriges tribe often buried women with
substantial grave goods2. Here we analyse 57 ancient genomes from Durotrigian burial
sites and nd an extended kin group centred around a single maternal lineage, with
unrelated (presumably inward migrating) burials being predominantly male. Such
a matrilocal pattern is undescribed in European prehistory, but when we compare
mitochondrial haplotype variation among European archaeological sites spanning
six millennia, British Iron Age cemeteries stand out as having marked reductions
in diversity driven by the presence of dominant matrilines. Patterns of haplotype
sharing reveal that British Iron Age populations form ne-grained geographical
clusters with southern links extending across the channel to the continent. Indeed,
whereas most of Britain shows majority genomic continuity from the Early Bronze
Age to the Iron Age, this is markedly reduced in a southern coastal core region with
persistent cross-channel cultural exchange3. This southern core has evidence of
population inux in the Middle Bronze Age but also during the Iron Age. This is
asynchronous with the rest of the island and points towards a staged, geographically
granular absorption of continental inuence, possibly including the acquisition of
Celtic languages.
The structure of a society is shaped by the residence patterns of its mar-
ried couples
4
. Matrilocality, whereby partners predominantly reside
with or near the wife’s parents, is relatively rare in modern ethnographic
databases5,6, whereas patrilocality is by far the most common system.
Furthermore, in most European Neolithic, Copper and Bronze Age
sites with sufficient genomic and archaeological data, evidence of
patrilocality and patriliny has been reported7–13.
Despite being on the cusp of the historical era, little is known about
the social structures of the Iron Age peoples of Britain. In the early
centuries , Ptolemy described the locations of various ethne on the
island with names of Celtic origin (Extended Data Fig.1), and Caesar
referred to civitates. These ambiguous terms are often translated as
‘tribes’, although the complexities of such group identities are not well
understood. Interestingly, two of the earliest recorded British rulers
were women, Cartimandua and Boudica, suggesting that both sexes
could reach the highest political status. From Cartimandua’s 30-year
reign of the Brigantes, a tribe covering much of northern England, we
learn that women could inherit property, divorce and lead armies to
great effect1. In the east of England, Boudica of the Iceni famously led an
uprising that destroyed three Roman towns and challenged the author-
ity of the imperial government
14
. Furthermore, Julius Caesar noted,
in the mid-first century , that British women could take multiple
husbands (De Bello Gallico). However, such social descriptions are seen
as suspect, biased towards what would have seemed exotic to a Medi-
terranean audience that was immersed in a deeply patriarchal world1.
The distributions of grave goods in multiple western European Celtic
cemeteries have been interpreted as supporting high female status15.
British archaeological evidence, however, is limited as Iron Age human
remains are rare, with individuals perhaps predominantly cremated,
excarnated or deposited in wetlands. The Durotriges tribe, who occu-
pied the central southern English coast around 100  to  100, were
one exception, depositing their dead in formal cemeteries of flexed
inhumations (Fig.1c and Supplementary Note1). Interestingly, it is
women who are more commonly associated with a greater number
and diversity of prestige items in these burials, hinting at high status
and perhaps a matrifocal society2.
The genomic variation of Iron Age Britons has been investigated
16–19
,
but with limited data from single cemeteries that could clarify social
customs relating to kinship and marriage. Genomic survey has con-
tributed to debates on the spread of Celtic languages (Supplementary
Note1.6), with the Middle to Late Bronze Age identified as a candidate
window for arrival based on the inference of large-scale migration to
the island during this period, followed by substantial genetic isola-
tion in the Iron Age17. However, the characterization of gene flow into
https://doi.org/10.1038/s41586-024-08409-6
Received: 7 May 2024
Accepted: 14 November 2024
Published online: 15 January 2025
Open access
Check for updates
1Department of Genetics, Trinity College Dublin, Dublin, Ireland. 2Department of Archaeology and Anthropology, Bournemouth University, Bournemouth, UK. 3Department of Life and Environmental
Sciences, Bournemouth University, Bournemouth, UK. 4School of Mathematics, University of Bristol, Bristol, UK. 5Institute of Genomics, University of Tartu, Tartu, Estonia. 6Department of
Linguistics, University of Hawai‘i at Mānoa, Mānoa, HI, USA. 7DFG Center for Advanced Studies, University of Tübingen, Tübingen, Germany. 8Éco-anthropologie, Musée de l’Homme, Paris, France.
✉e-mail: cassidl1@tcd.ie
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Nature | Vol 637 | 30 January 2025 | 1137
Britain requires further refinement through haplotypic analysis and
regional dissection. Here, we sequence 55 genomes from Durotrigian
and other cemeteries at Winterborne Kingston (WBK), Dorset, along
with two well-furnished female Durotrigian burials from Maiden New-
ton and Langton Herring2,20 (Supplementary Table2 and Supplemen-
tary Note1). These reveal a community characterized by female-line
descent. When combined with data from other British Iron Age sites,
our analyses find that matrilocality is widespread, reveal fine-scale
genealogical networks that align with geographical boundaries and
show a genomic footprint of Iron Age immigration on the south coast
that is reflective of both contemporary Roman writing and archaeo-
logical datasets.
Matrilocality in Durotrigian society
Excavations at WBK in coastal southern England have revealed consid-
erable evidence for settlement, spanning the later Bronze Age, around
1000 , to the post-Roman period, around  500, including several
small Durotrigian-type cemeteries from the later Iron Age20 (Fig.1b and
Supplementary Note1). Genomic data were retrieved for all 55 skeletal
samples taken from the site (Supplementary Table1), with 40 achieving
a coverage high enough for genotype imputation and robust identifica-
tion of genomic segments that were identical by descent (IBD) between
individuals21 (>0.3×; Methods and Supplementary Note3). This revealed
WBK to be the burial ground of a large kin group during the Durotrigian
period of the site’s usage (around 100  to  100; Fig.1b), with 30 of
40 individuals possessing at least one relative of approximately the
seventh degree or closer (Supplementary Table10; see Supplementary
Note4.3 for exact criteria). An additional four low-coverage members
of this kin group were identified through allele-matching analysis.
Strikingly, more than two thirds (24/34) of the genetically identified
kin belong to a rare lineage of mitochondrial haplogroup U5b1 (Fig.1d)
that has not been observed previously in ancient sampling and that has a
frequency of only 3×10
−5
in modern data
22
(Supplementary Table7 and
Supplementary Note2.4). The predominance of this single matriline is
not skewed by an abundance of siblings, with only two pairs of sisters
(all adults) observed (Fig.1a). Additional downstream mutations distin-
guish four subclades in this haplogroup that are unique to WBK. Using
one of the faster estimates of the mitochondrial DNA (mtDNA) muta-
tion rate23 (4.72×10−7mutations per site per generation), we estimate
15 19
105
16182C
93G
15607G
15928T
iii
~3
4–5
≥5
31
18
195
06
22
30 16
13011T 14544A
151T
05
ii v
iv
i
i
14
31
4–6
36
~2
1
1
4–7 3–4
0–1
mtDNA
Y chromosome
0
None
5
700 BC 500 BC 300 BC AD 100 AD 500 F
Date
Weighted
relatedness
No date By sexEarly Iron Age
Durotrigian period
Late Iron Age Sub-Roman
a
b
d
29
101
103
106
21
192
08
Male
Female
Unknown
c
R-L21-S1051
R-L21-A9871
R-L21-Z2186
R-L21-BY7804
R-L21-CTS6919
R-DF27-Y14529
R-DF27-L617
R-DF27
xL617, xY14529
G-Z725-Z726
R-Z42
I-L460-Z105
U5b1 and
sublineages
K1a+195
U5a1a1
J2a1a1
H7b
H4a1a1a
J2a1a1d
≥5
34 40
2
3–4
≥5
3–4
2–3
~3
107
23
17
42
06
12
03
20
05
39
09
33
102
16
11
02
Middle Iron Age Roman
AD 300100 BC M
Fig. 1 | The W BK pedigre e. a, The best-fit ting pedig ree (for uncertai nties, see
Supplemen tary Note4). Sampled i ndividuals are ou tlined in black wi th WBK ID
number and a re coloured by mtDN A haplotype . The founding U5 b1+16189+
@16192 female is show n at the top, with her four d escendant s with denovo
mutation s underneat h. Further des cendants are co nnected w ith dashed line s.
Matings b etween des cendants of the fou nding female are show n in bold,
labelled i–v. Deduc ed relationsh ips not fitt ed on the pedig ree are shown wit h
light-grey lines , with the estim ated degree of re latedness . b, Weighted
relatedne ss of each genom e plotted versu s the point carb on-14 date estimate
(average 95% conf idence range: 20 2years). For each, the sum of th eir total
number of bio logical kin ship links (seventh de gree or less) is show n, inversely
weighted by t he degree of the re lationship. Ind ividuals are colo ured by mtDNA
haplotype; grey indicates singleton haplogroups . The Durotrigian period
(solid line) and the ra nge of dates of family m embers (dashed lin e) are
indicate d. The summed re latedness is al so shown in box plot s (Tukey) by
sex for individ uals in the latte r range; a signif icantdifferen ce between m ales (M)
andfemales (F) is ob served (Welch ’s t-test, two-taile d, P=0.029). The frequen cy
of the domina nt mtDNA linea ge for each groupis the pro portion of ea ch boxplot
body in colour, which was also significantly different (two-tailed Fisher’s exact
test, P=0.02). c, A flexed i nhumation excavate d at WBK, typi cal of the
Durotrig ian cultural zone (ph oto credit: Bour nemouth Univer sity). d, mtDNA
and Ychromosom e haplogroup fre quencies for indi viduals with at le ast one
genetic rel ative and suff icient Y chromo some coverage (Supplementar y Table 9).
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1138 | Nature | Vol 637 | 30 January 2025
Article
that at least 420 female births to lineage mothers would be required to
result in this level of within-clade diversity (Supplementary Note2.6),
implying a long-term association between this haplotype and WBK.
By contrast, we find that Y chromosome diversity is high (Fig.1d and
Supplementary Note2.8), and runs of homozygosity (ROH) indicate
that this was an outbreeding community (Supplementary Note5.5).
Theory, modelling and surveys of modern populations24,25 have dem-
onstrated that such patterns are generated by matrilocal customs (that
is, male-biased dispersal).
To confirm matrilocality at WBK, we carried out two types of simula-
tion (Supplementary Notes2.10 and 4.5). First, we modelled different
rates of male and female migration between demes in a population and
estimated the resulting uniparental haplotypediversity (h) (Methods
and Supplementary Note2.2). These simulations indicated an outward
female migration rate close to zero and a male rate between 0.15 and
1 per generation. Second, we simulated the distribution of autoso-
mal and Xchromosome kinship coefficients in a seven-generation
pedigree whose members practised alternately (1) patrilocality, (2)
matrilocality or (3) mixed residence. Again, the observed data are
consistent with matrilocality (Supplementary Note4.5). The earliest
incidence of the dominant mtDNA lineage is in two second-degree
relatives (346 to 51 calibrated (cal) ), with the last observation in the
Roman period (cal  31 to 212), when British Celtic societies under-
went radical changes (Fig.1b). Accordingly, the latest family member
was buried following a new funerary rite of extended inhumation
(WBK36; cal  82 to 316).
Marriage custom in an Iron Age community
We reconstructed the most parsimonious pedigree for the core kin
group, which further confirms matrilocal traditions at WBK coupled
with male mobility (Fig.1a and Supplementary Note4). We found only
one patrilineal relationship greater than the first degree (WBK02 and
WBK195), and we infer this to involve multiple partnerships with matri-
line women across generations. An adult woman (WBK31), her daughter
(WBK22) and her adult granddaughters (WBK15 and WBK19) are all
buried at the site, as well as an inferred matrilineal great-grandson
(WBK12) of WBK31 through a different male partner. There is also one
unusual case of a double relationship in our pedigree; from IBD seg-
ment length distributions, we can conclude that WBK17 is most likely
the son of stepchildren whose parents’ marriage produced the sisters
WBK34 and WBK40 (Supplementary Note4.8).
When we consider individuals dating to the Durotrigian period, we
find that males show significantly lower levels of genetic relatedness
with other individuals and are significantly overrepresented among
non-matrilineage individuals (Fig.1b). Six individuals, all male, show
no detectable genetic connection to the WBK kin group(that is,they
are not members of the dominant matrilineand have no identified
relatives), although they may still have been family members (for
example, inward-migrating spouses or fostered children). Four of
the six who were adult or adolescent at death were buried in typical
Durotrigian fashion, three with grave goods comprising locally manu-
factured ceramic vessels, implying their integration in the community.
When considering genetically related individuals, we find eight of
ten family members who do not belong to the dominant mitochon-
drial haplogroup are male. We infer two marriages between these
non-lineage men and lineage women, including the outlier WBK02
whose ancestry derives mainly from continental Europe (Extended
Data Figs.2 and 3).
We note that theco-burial of spouses is not typical of a society with
strict emphasis on matrilineal descent, in which men will frequently visit
or even reside with their matrilineal kin and are often buried alongside
them rather than with their wives
26
. Indeed, the integration of husbands
into their wives’ households can place strain on matrilineal systems in
which nephews inherit from their maternal uncles (the avunculate)
27,28
.
For this reason, matrilocality is thought to be more stable when there
is less property for male kin to control. It is associated with societies in
which wealth is concentrated in the land, which is typically abundant
and extensively farmed and owned by women, and in which men are
often absent (for example, because of warfare)27,29,30.
Interestingly, at WBK we infer five marriages in which both part-
ners descend from the founding female (Fig.1a), including three in
which both members are direct descendants through the female line.
However, these partners have no recent relatedness, as indicated by a
lack of IBD sharing and lack of ROH in their offspring (Supplementary
Note5.5), and the matriline couples belong to different subclades. This
suggests that the people of WBK had a deep knowledge of their own
genealogies, which may have been used to guide marital arrangements
among a pool of related groups in the local region. These patterns
are consistent with modern matrilocal populations
31
who typically
show increased rates of local endogamy (for example, marriages of
individuals from nearby villages or within the same village), which
can allow men to retain influence in their natal group through geo-
graphical proximity.
Matrilocality across Iron Age Britain
To place the WBK community in context, we searched for reduced
mitochondrial diversity as a signature of matrilocal practice through
space and time in Europe (Supplementary Note2.2 and Supplementary
Table13). We considered 156 archaeological sites (first-degree relatives
removed) spanning from the Neolithic to the Iron Age and observed
six outlying communities with extremely low levels of diversity (Fig.2
and Extended Data Fig.1), all from the English Iron Age: Worlebury
(Somerset), Bottle Knap (Dorset), Gravelly Guy (Oxfordshire), Trethel-
lan Farm and Tregunnel (Cornwall) and Pocklington (Yorkshire). We
further observed that the 11 lowest diversity estimates come from Brit-
ish Iron Age populations, as well as one English Middle to Late Bronze
Age site. By contrast, Ychromosome diversity is high (Supplementary
Table18 and Supplementary Note2.9), and patterns of ROH imply that
these were relatively large outbreeding communities
17
(Supplementary
Note5.5). At Pocklington
17
, the second-largest British cemetery sample
in the dataset, 28 of 33 individuals belong to one of three dominant
mtDNA haplogroups, which, in a manner akin to WBK, can be divided
into subclades defined by private mutations. Here, the main period of
burial activity was between 400 and 50 , but the first observation
of a dominant matriline pre-dates this in the Early Iron Age (I11033;
717–395cal ; Supplementary Table 12).
These results provide strong evidence that longevous matrilocal
communities were widespread across the island through the Iron Age
and may even have their origins in the preceding Bronze Age period.
Analyses of Bell Beaker and Early Bronze Age cemeteries in Britain
and Germany have produced evidence of patrilocality and emphasis
on patrilineal descent12,13,32, which, if reflective of the broader social
organization of this period in Britain, raises the interesting possibility
of a patrilocal society transitioning to matrilocality. This is a relatively
rare occurrence in ethnographic surveys, although these may not be
indicative of conditions throughout most of human history4,33.
High mitochondrial diversity at a site may not solely reflect residence
patterns but can also indicate an overall lack of biological relatedness
among individuals; indeed, in Iron Age Britain, mtDNA diversity shows
a significant (P=5.85×10
−7
) inverse correlation with the normalized
number of relative pairs identified using refinedIBD21 (Fig.2). However,
no similar reduction in mtDNA diversity is apparent for other prehis-
toric periods, despite the presence of multiple sites with high levels of
biological relatedness (Fig.2), implying that matrilocal practices were
not widespread in Neolithic or Bronze Age Europe. By contrast, when
we consider Ychromosome diversity in British Iron Age populations,
no correlation with the number of relative pairs is identified (r=0.06,
P=0.77; Supplementary Note2.9).
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Nature | Vol 637 | 30 January 2025 | 1139
IBD segments reveal regional structure
We found 30 instances of genetic relatives (more than 24cM shared)
between sites (most of which were between 2km and 40km distant),
none of whom shared mtDNA haplotypes (Extended Data Fig.4, Sup-
plementary Note5.6 and Supplementary Table14). By contrast, 51% of
within-site pairs share their mtDNA. For example, Dibbles Farm and
Worlebury Hillfort on the Bristol Channel coast share eight relative
pairs (30–55cM IBD) and each site is dominated by a different matriline
(Fig.2 and Extended Data Fig.1), suggesting that the movement was
of male marriage partners. Similar patterns are seen in East Yorkshire,
the region of the distinctive Iron Age Arras Culture associated with the
Parisi tribe referenced by Ptolemy. We observe extreme levels of IBD
sharing among all sites east of the River Derwent boundary, implying
the existence of a cohesive social group in this territory (Extended Data
Fig.5). However, no shared mtDNA haplotype is observed between any
of these East Yorkshire sites.
To further characterize population structure in Iron Age Britain,
we carried out Leiden clustering (Methods) on a weighted network
graph of IBD sharing between archaeological sites (Fig.3a and Sup-
plementary Note5.7). Consensus clusters were identified across 100
independent runs. These show clear geographical patterning; for exam-
ple, subclusters in Scotland (greens), Yorkshire (blues), the Midlands
(aquas) and the southwest (purples) all emerge. WBK is placed within
a Dorset cluster (red), which maps onto the known distribution of later
Iron Age ‘Durotrigian style’ coinage34,35 (Fig.3c). Interestingly, several
clusters encompass both continental and coastal British sites, pointing
to cross-channel movements.
Patterns of IBD segment sharing also reveal differences in popula-
tion sizes across Britain and the continent (Extended Data Fig.6). The
south and east of England show markedly reduced levels of ROH and
within-region IBD sharing, indicative of higher population densities
and connectivity. These were very productive agricultural regions
where the first proto-towns (oppida) of southern Britain emerged in
the century before the Roman conquest of  43.
Iron Age migration into southern England
An increase in continental ancestry components has been described
for Iron Age genomes from the south of Britain (England and Wales)17
and has been interpreted as the result of large-scale movements into
the island during and before the Late Bronze Age (around 1000 to
875 ). This is detectable as a rise in Early European Farmer (EEF)
ancestry (Supplementary Note6.2). When we incorporate our data,
we find a previously undetectable significant (Welch’s t-test, two-tailed,
P=0.0005) increase in EEF ancestry between the Early and Late Iron
Age (from 39.7%±0.2% to 41.8%±0.5%), driven by genomes from
southern regions along the central and eastern English Channel coast,
including those from the Durotrigian territory (Fig.3d and Supplemen-
tary Table25). These regions emerged archaeologically as a core of
unprecedented continental influence during the Middle Bronze Age,
with cross-channel communities exhibiting parallel developments
0 1.0 0 1.0 0 1.0
0
0.5
1.0
Continental
Insular
Neolithic Copper and Bronze Age Iron Age
Normalized number of relative pairs
mtDNA haplotype diversity (h)
0
0.25
0.50
0.75
1.00
h value
Worlebury (n = 7)
Gravelly Guy (n = 9)
Trethellan Farm (n = 6)
Pocklington (n = 33)
WBK
Bottle Knap (n = 2)
Tregunnel (n = 2)
P = 0.001
r = –0.449
P = 0.230
r = –0.177
P = 0.115
r = –0.253
0.50 0.5 0.5
Fig. 2 | Reduc ed mitocho ndrial divers ity in Brit ish Iron Age co mmunities .
Trends in mtDNA haplo type diversi ty (h) for archaeolog ical sites wit h two or
more indivi duals after pru ning of first-deg ree pairs. Hap lotype diver sity is
calculate d as the probabilit y that two random ly selected h aplotypes ar e
different (M ethods). In the bot tom panels, the h valu e is plotted ag ainst the
normalize d number of relat ive pairs seen for ea ch site (1, all pairs are ge netic
relatives; 0, no pai rs are genetic rela tives; Suppleme ntary Note5. 3). The shaded
area repres ents the95% conf idence inter val around the f itted line .There is a
strong neg ative correlati on between m tDNA diversit y and the number of
relatives pre sent for Iron Age sit es (Pearson cor relation coef ficient, P=0.0 01,
r=−0.449), which is not ob served in prev ious period s of prehistory. Whe n each
period is further split into continental and insular (UK and Ireland) individuals
(diamonds and circles), we find that the only significant correlation observed
is for the Briti sh Iron Age (Pearson c orrelation coe fficien t, P=5.853×10−7,
r=−0.717). T he top panels show th e geographic al distributi on of these h values
for sites wit h evidence of bur ial guided by kin ship (at least one pair of g enetic
relatives pre sent). Of the tota l 156 sites con sidered, 13 sit es are less diver se than
WBK: 1 2 from Britain an d 1 from a Celtic La Tèn e period ceme tery (320–180 )
in Hungar y17. The sample s izes for the h value and no rmalized relati ve pair
estimat ion for all sites are pre sented in Suppl ementary Table13.
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1140 | Nature | Vol 637 | 30 January 2025
Article
in disposal of the dead, settlement architecture and material culture
over centuries, suggestive of high levels of population mobility
3
. Close
cross-channel relations persisted throughout the Iron Age, when much
of Britain seems to have developed a more regional and distinctively
insular cultural footprint.
When we split the genomic dataset into ‘channel core’ and ‘peripheral’
regions, we find that the rise of EEF ancestry during the Bronze Age
was not a unitary process. Rather, the major increase in the channel
core zone occurs across the Early to Middle Bronze Age, whereas a
centuries-long lag is observed in the peripheral regions. For example,
further regional division shows no increase in EEF ancestry in northern
England from the Early Bronze Age until the Early Iron Age (around
750–400 ; Extended Data Fig.7).
The impact of continental gene flow specific to the channel core
zone is visible in principal-components analysis (PCA) of modern and
ancient western Europeans (Extended Data Fig.2), as well as patterns
of haplotype copying from continental populations, characterized
using ChromoPainter
36
(Fig.3b). We used SOURCEFIND
37
to decom-
pose the ancestry of Iron Age genomes into contributions from Early
Bronze Age British and continental groups and further validated our
results using an alternative approach of non-negative least squares
38
(NNLS) with a different panel of surrogates (Methods and Supplemen-
tary Note6.3). Overall, we estimate an average contribution of 73%
(estimated by SOURCEFIND; NNLS estimate: 75%) from the British
Early Bronze Age (2500 to 1500cal ) to the English and Welsh Iron
Age population (800  to  50). Although this value is larger than
the estimate of a previous study
17
, which inferred a 50% long-term
replacement rate for the gene pool, it is in agreement with the reported
dilution of British- and Irish-specific R1b-L21 haplogroup Y chromo-
somes by one quarter17.
A sharp dip in Bronze Age continuity is seen along the channel
coast (Fig.3b and Extended Data Fig.8). This is centred on Hamp-
shire (SOURCEFIND estimate of 60%), a region traditionally associated
with Belgic tribes that Caesar mentioned as having migrated from
Gaul3. Both Hampshire and the neighbouring Durotrigian zone show
independent and significant increases in EEF ancestry between the
Early and Late Iron Age (Extended Data Fig.7). Notably, the Durotrig-
ian territory was home to a major port at Hengistbury Head, one of
the focal points of intensifying cross-channel networks as Roman
influence spread across Gaul39. With fewer samples for analysis, hap-
lotypic data provide less resolution on fine-grained temporal trends
but identify numerous genetic outliers in the Middle to Late Iron Age,
all from the channel core region, which are not discernible when EEF
ancestry alone is considered (Extended Data Fig.3; see Supplementary
Note6.3 for further discussion of genetic outliers). These outliers
include one of the most elaborate warrior burials known for Iron Age
England (North Bersted on the channel coast; around 50cal ), which
has been proposed, on the basis of isotopic signature and burial rite,
to belong to a stream of cross-channel migrants, fuelled by Caesar’s
conquest of Gaul40.
Trethellan Farm
Tregunnel
Harlyn Bay
RAF St Athan
Football Field
Bottle Knap
Winterborne Kingston
Maiden Newton
Langton Herring
Ham Hill
Cadbury Castle
Saxon Way
Amesbury Down
Lechlade Memorial Hall
Broom Quarry
North Bersted
Moulsecoomb
Isles sur Suippe
Buchères
Attichy-Bitry
Faux Vesigneul
Barbuise La Saulsotte
Velsen-Hoogoventerrein
Goxwiller
Urville-Nacqueville
Nordhouse
Drifeld Terrace
Slonk Hill
Rowbarrow
Kingsdown Camp
Battlesbury Bowl
Casterley Camp
East Kent Access Road
Greystones Farm
Cleevelands
Dibbles Farm
Worlebury
Highsted
Broxmouth
House of Binns
Law Road
High Pasture Cave
Applecross
Bu
Buckquoy Birsay
Knowe of Skea
Thame
Wattle Syke Dalton Parlours
Teversham Marshalls
Burstwick
Melton
Nunburnholme Wold
Pocklington
Town Pasture
East Coast Pipeline field 9
East Coast Pipeline field 16
Hinxton
Gravelly Guy
Yarnton
Over
Bradley Fen
Meare Lake Village West
Cliffs End Farm
Linton
Winnall Down
North Perrott Manor
Barton-Stacey Pipeline
New Buildings
Danebury
Suddern Farm
Trumpington Meadows
Carsington Pasture
Fin Cop
Dorset
South Coast
Yorkshire
Southwest
Continental
North
Scotland
South
Scotland
Hampshire
a
Southeast (2)
Southeast (1)
20
30
40
50
2500 2000 1500 1000 50
00
Date (cal BC)
EEF fraction (%)
Channel core
Peripheral
c
British
Bronze Age
ancestry
0
0.25
0.50
0.75
1.00
W
D
o
b
unn
i
D
urotr
ig
e
s
A
tre
b
ate
s
b
c
d
North Somerset
Midlands
Fig. 3 | IBD co mmunitie s in Iron Age Bri tain show f ine-grai ned
geograp hical struc ture and incl ude connec tions acro ss the Englis h
Channel. a, The clusters are b ased on the con sensus of 100 ru ns of the Leiden
algorithm on a we ighted graph o f IBD shared bet ween archaeo logical site s and
show geogra phical integr ity. Twelve major clusters (def ining nodes m arked
with symb ols) are labelled on th e basis of geogr aphical aff iliations, w ith further
substructure within clusters emphasized usin g different colour shades. The
cross-cha nnel clusters ar e highlighted w ith dashed line s joining neare st
geograph ical neighbo urs across the ch annel. b, An inter polated map show ing
the distri bution of Briti sh Bronze Age ance stry acros s Iron Age Britain , based
on average values generated using ChromoPainter NNLS38 and SOURCEFIND37
approache s. The lowest val ues are seen alon g the south-ce ntral coast. S ites
with les s than 75% contribut ion are marked in black . c, A close-up show ing most
of the sites f rom the Dorset c luster (red circles) plac ed within the re gional
distribu tion of Durotri ges coin find s. WBK is denot ed by ‘W’. The distr ibutions
are plotte d according to refs . 34,35. d, The EEF ance stry propor tion through
time for the cha nnel core region o f continenta l influenc e (blue; outlined w ith
dashed lin ein b) shows a Late Iron Age incre ase not obser ved in the sample
from the res t of England and Wales ( black). The chann el core zone is eas t of
longitud e −2.8° (western e dge of the Durotrig ian zone) and south of l atitude
51.5° (R iver Thames). The p eriod bet ween 1000 and 875  (g rey rectangl e) has
been previ ously assoc iated with an in crease in EEF anc estry in so uthern Brit ain17.
This wind ow is populated mo stly by high-EEF sa mples from the ch annel core,
whereas da ta points direc tly precedin g this window are most ly from the
peripher al regions tha t retained a lower le vel of EEF ancestr y throughout th e
Middle Bronz e Age (Extended D ata Fig.7 and Supple mentary No te6.2).
Content courtesy of Springer Nature, terms of use apply. Rights reserved

Nature | Vol 637 | 30 January 2025 | 1141
Insular continuity
Regional continuity is strongest in Scotland, estimated at 92%, with
contributions preferentially coming from the Scottish Early Bronze
Age population (Extended Data Fig.8 and Supplementary Note6.3).
Large components of Early Bronze Age ancestry are also seen in
northern England (88%) and the southwest (78%). Outside of Britain,
a single Netherlands Late Iron Age genome also shows some evidence
of population continuity, deriving its ancestry almost entirely from
the Netherlands Bronze Age population in SOURCEFIND analysis. By
contrast, French populations show a diversity of components, mainly
from French and German sources, but with large minor components
of Czech Iron Age ancestry in the east and Spanish Bronze Age ances-
try in the south, highlighting France’s position as a crossroads in the
Celtic-speaking world. We note one French outlier from the coastal site
Urville-Nacqueville
41
, which faces Dorset across the English Channel
and contains Durotrigian-style flexed burials in shallow oval graves.
This individual has an estimated 72% contribution from the British
Bronze Age, implying that gene flow occurred in both directions across
the channel.
Conclusions
The diverse geography of Britain lends itself to regionality, which mani-
fests across archaeological periods
3
. In its Iron Age we characterize
fine-grained geographical genetic structure, shaped by natural ter-
ritorial boundaries such as rivers. The peripheral regions—including
Scotland, Cornwall, Wales and northern England—show signatures
of insularity. The southern channel core is an exception, showing
reduced genomic continuity with the British Early Bronze Age, sites
with cross-channel IBD affinities, indications of larger population
size and individuals with outlying ancestries. In this region, we see a
Middle to Late Iron Age spike in EEF ancestry, indicative of substantial
cross-channel movements that match textual and archaeological evi-
dence for an intensification of contact and exchange, driven, at least
latterly, by Roman expansion into Gaul.
The flow of genes across the channel through the Bronze and Iron
Ages provides a wide window for the arrival of Celtic languages. Sub-
stantial components of continental ancestry are present in the channel
core region by the Middle Bronze Age. However, it is probable thata
second surge of EEF ancestry in the Iron Age would have influenced any
version of insular Celtic alreadyspoken in the channel region, and we
note that the Celtic languages of southern Britain (Brittonic) and Gaul
share a number of innovations not seen in more peripheral branches,
such as the Goidelic languages of Irelandand Scotland
42
. Given the
strong signatures of Early Bronze Age continuity in most British regions,
any language introduction after this period would have probably been
driven by a demographic minority, potentially an elite.
It is possible that the pervasive matrilocal traditions of Iron Age
Britain were also introduced from the continent, but, notably, reduced
mtDNA diversity is pronounced in our peripheral populations (Fig.2
and Extended Data Fig.1). Matrilineal succession has previously been
proposed for continental Celtic societies, on the basis of the discovery
of a likely avuncular relationship between two ‘princely’ burials of the
Hallstatt elites in Central Europe
43
. Matrilineal institutions may also
have been present in the British Iron Age, given that social units based
on unilineal descent are common in large agricultural societies that
practise unilocal residence
4
. However, the burial of male spouses at
WBK suggests that, if matrilineal descent groups existed in this society,
they were limited in their function26. We note that in matrilocal socie-
ties with a weak avunculate, mother–daughter–sister relationships are
generally given more emphasis, with women tending to enjoy relatively
higher status and control over property27.
Both matrilocality and matriliny are predicted by cultural factors
that increase female involvement in subsistence labour and decrease
paternity certainty
28,29,44–46
. External warfare can encourage both of
these through male absence and has long been theorized to induce tran-
sitions to matrilocality through various mechanisms45,47,48, a hypothesis
recently strengthened through quantitative modelling
49
. Matrilocality
also predicts a history of migration into a new territory, which often is
accompanied by frontier warfare
4,45
. The British Iron Age was debatably
a time of high societal violence, indicated by the early proliferation of
hillforts, weapons, human remains displaying violence-related injuries
and instances of intergroup conflict recorded by Roman writers such as
Julius Caesar and Tacitus
50–53
. Importantly, although matrilocality does
not necessitate female political and social empowerment, it is strongly
associated with these
4,27,54–56
and resonates with Roman descriptions
of Celtic women
1
. Although classical depictions of conquered peoples
are often viewed with scepticism, we find here some truths in these
writers’ appraisal of Iron Age Britain.
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Methods
Data generation
We sampled 57 burials for DNA sequencing from three sites in
Dorset2,20,57–59—WBK (n=55), Langton Herring (n=1) and Maiden New-
ton (n=1). Petrous bones were preferentially sampled (n=46), along-
side tooth roots (n=10) and a single phalanx. Sample processing took
place in clean-room facilities dedicated to ancient DNA research at Trin-
ity College Dublin. DNA extraction was carried out following various
protocols
60–63
detailed in Supplementary Table4. DNA extracts were
treated with USER enzyme to reduce post-mortem deamination lesions,
and double-stranded libraries were created for Illumina sequencing
61,64
.
Library aliquots were amplified using Accuprime Pfx Supermix (Life
Technologies) with sample-specific index primers (Supplementary
Table5). Paired-end or single-end sequencing was carried out on MiSeq,
HiSeq 2500 and NovaSeq 6000 platforms (Supplementary Table5).
Sequence data processing
Exact P7 index matches were required for demultiplexing, with up to two
mismatches allowed in the P5 index for paired-end data. Adapters were
removed from single-end data with cutadapt
65
and from paired-end data
with AdapterRemoval66. Paired-end reads with an overlap of 11bp were
collapsed. Singleton reads and collapsed reads that required quality trim-
ming were discarded. Reads were mapped to GRCh37 with decoy contigs
(hs37d5) using BWAsoftware
67
with non-default parameters -l 16500,
-n 0.02 and -o 2. Reads were sorted with SAMtools
68
, polymerase chain
reaction duplicates were removed with Picard Tools v.2.0.1 and indels
were locally realigned using GATKsoftware (v.3.7.0)
69
. Reads with a map-
ping quality below 25 and a read length below 34bp were removed. Finally,
we ‘soft-clipped’ the data by reducing the Phred quality scores of the two
terminal base pairs at the 5 and 3 read ends to a score of 2. Comparative
ancient genomic sequence data were downloaded and realigned from
either unaligned FASTQ (when available) or BAM (aligned binary align-
ment map) files following the same pipeline (Supplementary Table12).
Uniparental markers
A detailed description of uniparental marker analysis is found in Supple-
mentary Note2. In brief, for mitochondrial haplotype calling, unfiltered
read data aligned to GRCh37 were realigned to the Cambridge Reference
Sequence for human mtDNA and subjected to the same downstream
filters as described for GRCh37 alignments. Variants were called using
BCFtools (v1.10.2)70, and the resulting VCF (variant call format) file was
inputted into HaploGrep2 (ref. 71) to assign haplogroups based on
Phylotree (Build 17)72. To estimate contamination, we calculated the
fraction of minor alleles at HaploGrep-identified single-nucleotide
variant sites present in the sample (Supplementary Table7). Haplotype
diversity (h) for archaeological sites was calculated as the probability
that two randomly selected haplotypes were different
73,74
(Supple-
mentary Table13). For Ychromosome haplotype calling, we relaxed
several filters in our read processing pipeline: (1) we did not require an
exact P7 index match; (2) we included singletons and collapsed reads
that required quality trimming; (3) we filtered for a mapping quality
above 20 and read length above 30bp; and (4) we did not carry out
soft-clipping. We used the Pileup tool from GATK (v.3.7.0)69 to extract
base calls for positions in the International Society of Genetic Geneal-
ogy (ISOGG)database of Ychromosomal markers (version 15.73, 11 July
2020) and The Big Tree database (https://www.ytree.net/). Base calls
below a quality of 30 were removed. The allelic state for each male
sample at relevant markers was then assessed (Supplementary Table9).
Haplogroups used for within-site estimates of Ychromosome diversity
in Britain are presented in Supplementary Table18.
Pseudo-haploid analysis
We used pseudo-haploid genotypes for PCA and quantification of EEF
ancestry. We used the Pileup tool from GATKsoftware (v.3.7.0)
69
to
extract base calls over single-nucleotide polymorphism (SNP) sites in
the 1,240k panel
75
for relevant genomes and selected one base call at
random (base quality >30) for each site to generate pseudo-haploid
genotypes. We merged 1,240k genotypes for 534 Iron Age individu-
als
17–19,41,61,76–80
with a dataset of 5,326 modern individuals from western
Europe
38,81
and, using approximately 266,000 sites common to both
datasets, projected ancient genomes onto a PCA plot of modern vari-
ation using smartpca (version 16000) from EIGENSOFT82. We quanti-
fied EEF ancestry in British Iron Age genomes following a previously
described procedure
17
. In brief, the qpAdm tool
83
, implemented in the
ADMIXTOOLS2 R package, was used to model British Bronze and Iron
Age genomes as a mixture of western hunter-gatherer, EEF and steppe
pastoralist ancestries (Supplementary Tables12 and 1 5). Whole-genome
sequence data, rather than targeted SNP capture, were used for source
and reference outgroup populations. Source populations61,76,79,84–87
were a set of Mesolithic individuals from northwest Europe (n=13),
Yamnaya pastoralists (n=6) and Early Neolithic Europeans from cen-
tral and southeastern Europe (n=9). Reference populations79,84,88–90
were a set of Mesolithic individuals from Latvia and Romania (n=6),
Afanasievo pastoralists (n=4), Anatolian Neolithic farmers (n=11) and
10 modern-day Mbuti individuals from the Congo region of Africa
91
.
Further information on PCA and qpAdm analyses is provided in Sup-
plementary Note6.
GLIMPSE imputation
We carried out genotype imputation on a dataset of 2,054 ancient
individuals, including 42 individuals from the current study using
GLIMPSEsoftware
92
(Supplementary Table12). This included both
whole-genome sequence (>0.1×) and targeted SNP capture (more than
300,000 calls across the 1,240k panel) datasets. After imputation,
we further filtered for low-coverage individuals by extracting 1,240k
panel positions and removing individuals for whom more than 40% of
those positions had a genotype probability below 0.99. Stricter down-
stream filters were subsequently applied depending on the downstream
analysis. To avoid any potential batch effects, we imputed each sample
individually with GLIMPSE using the 1000 Genomes Project haplotype
reference panel93. We used reference datasets and pipelines available
on the software’s webpage (https://odelaneau.github.io/GLIMPSE/
glimpse1/).
IBD segment identification
Four datasets of GLIMPSE-imputed diploid genotypes (genotype prob-
ability >0.99) were subjected to IBD segment identification (Supple-
mentary Table12). To identify segments, each of the four datasets was
subjected to further phasing and imputation using Beagle5 (ref. 94),
followed by refinedIBD analysis (Supplementary Note3). Different sets
of variant sites were used as input into both Beagle5 and refinedIBD to
test performance and maximize IBD segment retrieval. This resulted in
21 runs of refinedIBD in total, all carried out with default parameters.
The outputted IBD segments were subsequently subjected to different
merges and filters depending on the downstream application. Patterns
of IBD segment sharing were characterized within (ROH) and between
genomes, as well as within and between archaeological sites (Supple-
mentary Note5). We created a weighted graph of average IBD sharing
between Iron Age sites in northwest Europe and performed hierarchical
community detection using the Leiden algorithm95 implemented in the
R package leidenAlg (v1.1.1)96. We ran the leiden.community function
100 times with different seeds and constructed a consensus tree from
the output using the maximum clade credibility function available in
the R package phangorn (v2.11.1)97.
Pedigree construction
To reconstruct familial relationships at WBK, we used a combination of
data types, including (1) uniparental markers; (2) autosomal coefficients
of relatedness that were calculated using both allele-frequency-based
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Article
methods and IBD segment sharing; (3) IBD1 and IBD2 segment numbers
and lengths for genomes with more than 0.3× coverage, which were
compared with distributions simulated using ped-sim
98
; (4) longest
observed IBD segments within the genome; and (5) Xchromosome
IBD segment sharing. We determined the most likely genealogical
relationships for pairs of relatives of first- to fourth-degree relatives
(Supplementary Note4), allowing us to construct the most parsimoni-
ous pedigree for the WBK kin group.
Generating ancestry profiles with ChromoPainter
We used a dataset of 697 individuals17–19,41,76 –78,99–106 from the European
Bronze Age to medieval period for ChromoPainter
36
analysis (Sup-
plementary Table12). This dataset had been previously subjected to
Beagle5 imputation and phasing. We extracted 1,240k SNP sites and
rephased these using SHAPEIT2 (v2.r837)
107
. Two separate panels of sur-
rogate individuals were then selected and ChromoPainter was used to
generate co-ancestry matrices summarizing the amount of haplotypic
donations between pairs of surrogates following recommended guide-
lines. One panel (n=332) was then subjected to fineSTRUCTURE cluster-
ing using a previously described maximum concordance tree-building
method
38
. This panel was used to paint a set of British Iron Age genomes,
whose ancestry was then decomposed into contributions from the
identified fineSTRUCTURE clusters (n=17) using NNLS regression. The
second panel (n=307) was grouped into populations based on archaeo-
logical era and geographical location, rather than fineSTRUCTURE
cluster, and contained only targeted SNP capture data. This panel was
used to paint a larger set of British Middle to Late Bronze and Iron Age
genomes, as well as Iron Age genomes from France and the Netherlands.
Target populations included both whole-genome sequence and SNP
capture data. Ancestry profiles were then generated using SOURCE-
FIND37. SOURCEFIND was run using 50,000 burn-in iterations followed
by 200,000 sample iterations, thinning every 5,000 iterations. We set
the expected number of surrogates used to form the target as two, with
a total number of four surrogates allowed to form the target in each
iteration. We carried out 50 independent runs of the above procedure
and extracted the estimates with the highest posterior probability in
each run. The average of these 50 estimates (weighted by posterior
probability) was then calculated for each individual. This provided
us with a set of ancestry proportions for each genome. We observed a
strong correlation between SOURCEFIND and NNLS results with respect
to British Bronze Age haplotype contributions. Further details can be
found in Supplementary Note6.3.
Data visualization
The R package ggplot2 was used for figure generation (https://ggplot2.
tidyverse.org). Maps were generated using the R packages maps
(10.32614/CRAN.package.maps) and mapdata (10.32614/CRAN.pack-
age.mapdata). For Extended Data Fig.4, the retired rgeos package and
raster package were used, with data from the public Database of Global
Administrative Areas.
Reporting summary
Further information on research design is available in theNature Port-
folio Reporting Summary linked to this article.
Data availability
Aligned sequence reads are available through the European Nucleotide
Archive under accession number PRJEB81465. Other relevant data
are available from the corresponding authors on reasonable request.
Code availability
This study made use of publicly available software, referenced through-
out the main text and Supplementary Information.
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Acknowledgements The Durotriges Project is the cumulative product of a large team of
Bournemouth University staff, students and volunteers, and we acknowledge the input of all
involved since 2009. Special thanks must go to our hosts, R. Hill and family, for generously
permitting and facilitating all aspects of archaeological ieldwork. This work was funded by
Science Foundation Ireland/Health Research Board/Wellcome Trust Biomedical Research
Partnership Investigator Award no. 205072 to D.G.B., ‘Ancient Genomics and the Atlantic
Burden’, and aTaighde Éireann – Research Ireland Laureate Award (IRCLA/2022/126) to
L.M.C., ‘Ancient Isle’. We thank E. Kenny and the team at Trinseq (Trinity College Dublin) for
sequencing support.
Author contributions This study was designed by L.M.C., D.G.B. and P.E. L.M.C., V.M., E.M.B., I.J.,
M.M., H.L., C.G.O’C. and B.H. performed laboratory work. L.M.C. processed and analysed the data,
with contributions from D.L. M.R., G.D., M.S., P.C. and H.M. gave access to samples, provided
archaeological and osteological context, and aided in the interpretation of results. L.M.C. and
D.G.B. co-wrote the manuscript with considerable input from P.E., M.R., M.S., P.C. and D.L.
Competing interests The authors declare no competing interests.
Additional information
Supplementary information The online version contains supplementary material available at
https://doi.org/10.1038/s41586-024-08409-6.
Correspondence and requests for materials should be addressed to Lara M. Cassidy.
Peer review information Nature thanks the anonymous reviewers for their contribution to the
peer review of this work.
Reprints and permissions information is available at http://www.nature.com/reprints.
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Article
Extende d Data Fig. 1 | Mi tochondri al haplogrou p frequenc ies at Briti sh
Iron Age sites. Only sites wi th a sample size of si x or higher are cons idered and
first-deg ree relative pair s are removed. Of the 2 3 sites consid ered, 11 have a
h value of 1 (no haplot ype represe nted more than on ce). These are marked
as black poin ts on the map and are c omposed almo st entirely of gen etically
unrelated in dividuals. Pi e charts show hap logroup freque ncies for the
remaining 1 2 sites. Hapl ogroups with a c ount above one are emp hasised wit h a
black outlin e in the pie chart s. Dotted li nes are used to spl it haplogroups i nto
downstre am subclades ba sed on additio nal mutation s. Iron Age tribe n ames
recorded by cla ssical writ ers and their appr oximate geogra phic location s are
shown. Th e haplotype s of all British Iro n Age samples us ed in this analysi s are
given in Supplementary Table12.
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Extende d Data Fig. 2 | Pr ojection P CA of Iron Age Br itish and Eu ropean
genomes. The bot tom panel shows me dian position s of modern Europ ean
populatio ns (grey text w ith first thre e letters of co untry), Iron Age contin ental
populatio ns (black circle s with firs t three letter s of country) and Iron A ge
British and coastal French populations (coloured circles). Iron Age continental
French genome s have been split int o northern (nFr) and sout hern (sFr)
populatio ns. The map prov ides a colour key for Brit ish and coast al French Iron
Age populati ons (Supplement ary Table12). Sites with d ata for more than one
individual a re shown as large circ les with two let ter identif iers. The m edian
values for the se multi-indivi dual sites are plot ted in the top PCA p anel. The grey
box delimit s the area within t wo standard dev iations of the me an value for the
British Iro n Age population al ong PC1 and PC2 . Outlying in dividuals that f all
beyond this are a are plotted usi ng their two-le tter site ID. Two outliers f rom the
current stu dy are plotted us ing their full ID s (WBK02 and WBK 30). Two data
points from Urv ille-Nacqueville41 on the Normandy coast are also highlighted
(brown). One of the se (UN19) places fur ther away from French p opulations, in
agreement with SOURCEFIND results.
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Article
Extende d Data Fig. 3 | SOU RCEFIND an cestry pro files for a rchaeolog ical
sites and outlying individuals. Surrogate and ta rget individual s are listed
with their p opulation IDs i n Supplement ary Table12. Raw value s are available in
Supplemen tary Table17. The top rows show averaged pro files for Bronz e and
Iron Age archae ological sit es in Britain, Fran ce and the Nethe rlands. Briti sh site
profile s are outlined in bla ck if the site cont ains one or more indi vidual outlier s
(those poss essing a level of Br itish EarlyBronze Ag e ancestrytwo s tandard
deviation s below the popula tion mean). The bot tom row shows ance stry
profile s for these outly ing genomes. We no te thatall Middle and La te Iron Age
outliers de rive from the chan nel core region . We identify two pr eviously
reported17 EEF o utliers from Mar getts Pit and Cl iffs End Farm in Midd le-Late
Bronze Age Kent, w ho possess l ittle to no Briti sh Early Bronze Age a ncestry.
(BA: Bronze Age , EIA: Early Iro n Age, MIA: Midd le Iron Age, LIA: L ate Iron Age).
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Extende d Data Fig. 4 | Rel atives ident ified w ithin and bet ween sites i n Iron
Age Brita in based on I BD sharing . Genetic rela tives are def ined as individ uals
who share ≥ 24cM ac ross at least th ree IBD segm ents that are 4cM or lo nger
(Supplement ary Note5.2). a,This sh ows the frequen cy of relative pairs
identif ied within arc haeologica l sites, where a valu e of one indicate s thatall
pairs are relat ives and a value of zero in dicates no pair s are relatives. b, Th is
shows archae ological site s that are linked by gene tic relatives(Supple mentary
Table14; common colours deno te a set of linked site s). Most pairs of
relativesare ide ntified b etween neig hbouring site s (2–40km), but several
long-dist ance relative pair s are alsoidentif ied. An indiv idual from Winte rborne
Kingsto n (WBK01) has two relat ives at Carsing ton Pasture Cave in th e midlands
(red). Three Sco ttish sample s from norther n coastal site s also show a
relationship (green).
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Extende d Data Fig. 5 | An I BD enclave in Eas t Yorkshire. The n ormalised
amounts of I BD sharing (cM) bet ween 12 site s in northern E ngland. Each p anel
shows pairw ise values for a spe cific site (marke d with an X) and the ot her 11.
Sites high lighted in redtext are a ll located wes t of the River Der went
(highligh ted in white) and show exce ssive IBD shari ng with one anoth er. The
Roman burials of Driffield Terrace18 show low amount s of IBD sharing w ith sites
across the re gion, likely due to th e individuals bu ried there bei ng non-local in
origin.
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Extende d Data Fig. 6 | IB D sharing wi thin genome s, sites and r egions. Fo r
each mea sure, we calculate th e average total amou nt of IBD shared (cM),
represen ted using a colou r scale. For with in genome (i.e. run s of homozygosi ty)
and within si te comparison s we also show the average si ze of shared IBD
segmen ts. Within re gion sharing is c alculated as th e average amount of IBD
shared (cM) bet ween sites wit hin a geographic re gion, defin ed based on
present-day district divisions (see Supplementary Note5.4, Supplementary
Table12). It is a more robust me asure of relative p opulation size s than within
site and wit hin genome IBD sha ring, as thes e latter can be c onfounded by
kinship an d cultural pract ices such as con sanguineo us marriage. We se e lowest
values for wit hin region IBD sh aring in France and th e southeast of E ngland. For
within geno me IBD sharing , we take the populat ion average of the tot al length
of runs of hom ozygosity for ea ch archaeolog ical site. If the aver age total leng th
is above 3cM we plot th e site in the botto m panel. In Brit ain, sites wit h reduced
runs of homoz ygosity (top panel) a re concentrate d in south centra l and
southea stern region s indicative of large r population size s. Within site IB D
sharing (average le ngth shared be tween indivi duals in a site) is plotte d in a
similar fashion.
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Article
Extende d Data Fig. 7 | Ea rly European Farm er (EEF) Anc estry thro ugh time
in British regions. The perce ntage of EEF ance stry is show n on the y axis,
estimate d with qpAdm followi ng the approach of Pa tterson etal.(202 2)17. The
map shows the lo cation of Bronz e and Iron Age sites u sed for analysis. N o
genomes p ost-dating AD 25 0 were included. S amples are group ed by
geography, with t he “channel core” zo ne south of the Ri ver Thames sub divided
into wester n (dark red), central (red) and e astern (yellow) re gions. On the
right-hand side, E EF ancestry i s plotted agai nst the date est imate for each
genome and a rol ling average line is show n (window size: 500 ye ars, step size:
50 years). On the lef t-hand side, boxplots ( Tukey’s method) show the sprea d of
values for dif ferent 500-year t ime bins for each re gion. Thes e bins are
demarcate d with grey dash ed lines on the roll ing average plot. Tim e bin date
ranges are lab elled with res pect to the app roximate archaeo logical per iod they
centre on (EBA : Earlier Bronze A ge, MBA: Middle Bro nze Age, LBA: Lat er Bronze
Age, EIA: E arlier Iron Age, LI A: Later Iron A ge). Significant c hanges (Welch’s
t-test, two-t ailed; p<0.05) betwe en bins (n>4) are highlighte d with arrows.
The peri od between 10 00-875 BC is high lighted with a g rey rectang le in the
rolling average plo ts. This pe riod has been p reviously ass ociated with a
populatio n-wide increas e in EEF ancestr y in southern B ritain17.
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Extende d Data Fig. 8 | SOU RCEFIND An cestry P rofile s for western Iro n Age
populations. Surrogat e and target indiv iduals are liste d with their pop ulation
IDs in Supple mentary Table12 . Individual an cestry prof iles for the French si te
of Urville -Nacqueville are a lso shown41, t wo of which (white outlin e) are below
the coverage thre shold to which the re mainder of the dat aset was subj ect. They
are included h ere to demonstr ate that the indiv idual (UN19) with high leve ls of
British E arly Bronze Ageances try is likely an out lier at the site, in ag reement
with the proj ection PCA a nalysis (Exten ded Data Fig.2). Note th atthe French
Iron Age sampl es used as asurrog atepopulation are 1 240k SNP cap ture data,
while French tar getpopulations o n the map are whole geno meshotgun
sequence data.
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Corresponding author(s): Lara M Cassidy
Last updated by author(s): 21/10/2024
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Data collection Sequencing data was generated on Illumina platforms. This data was coanalysed with publicly available sequence data downloaded from ENA
using wget (GNU).
Data analysis Details on what each software was used for can be found in the methods section. Software names and versions are provided in a list below.
FASTQC v0.11.5
cutadapt v1.9.1
AdapterRemoval v2.3.1
BWA v0.7.5a-r405
SAMtools v1.7
GATK v3.7.0
Picard Tools v2.0.1
BCFtools v1.10.2
Haplogrep2 v2.2.9
smartpca v16000 (EIGENSOFT)
ADMIXTOOLS2 v2.0.4
GLIMPSE1 v1.1.0
Beagle5 v05May22.33a
refinedIBD v17Jan20.102
leidenAlg v1.1.1
phangorn v2.11.1
SHAPEIT2 v2.r837
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ChromoPainter v2
SOURCEFIND v2
fineSTRUCTURE v2
ped-sim
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Reporting on sex and gender Samples were defined as male or female based on read coverage across the sex chromosomes. No sex chromosome
aneuploidies were observed. Comparisons were made between the male and female populations buried at Winterborne
Kingston to draw inferences about kinship and marriage customs. When discussing these customs and other cultural
phenomena we use the terms men and women.
Reporting on race, ethnicity, or
other socially relevant
groupings
We do not bin samples by the socially constructed categories of race or ethnicity. We group samples by geographical region
or genetic cluster (defined based on haplotypic data).
Population characteristics All human samples are archaeological in nature. An osteological assessment of age-at-death, pathologies and trauma was
carried out.
Recruitment N/A
Ethics oversight N/A
Note that full information on the approval of the study protocol must also be provided in the manuscript.
Field-specific reporting
Please select the one below that is the best fit for your research. If you are not sure, read the appropriate sections before making your selection.
Life sciences Behavioural & social sciences Ecological, evolutionary & environmental sciences
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Life sciences study design
All studies must disclose on these points even when the disclosure is negative.
Sample size We exhaustively sampled all burials excavated at Winterborne Kingston. These were analysed with all publicly available data from the Iron Age
of northwestern Europe.
Data exclusions Data was excluded from certain analyses based on:
1. genomic coverage and genotype missingness
2. temporal range
3. geographic range
4. outlying genetic ancestry
Rationale for these exclusions is given in detail in the Methods section and Supplementary Information.
Replication N/A
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Randomization N/A
Blinding N/A
Reporting for specific materials, systems and methods
We require information from authors about some types of materials, experimental systems and methods used in many studies. Here, indicate whether each material,
system or method listed is relevant to your study. If you are not sure if a list item applies to your research, read the appropriate section before selecting a response.
Materials & experimental systems
n/a Involved in the study
Antibodies
Eukaryotic cell lines
Palaeontology and archaeology
Animals and other organisms
Clinical data
Dual use research of concern
Plants
Methods
n/a Involved in the study
ChIP-seq
Flow cytometry
MRI-based neuroimaging
Palaeontology and Archaeology
Specimen provenance All samples were obtained from the Department of Archaeology and Anthropology, Bournemouth University, United Kingdom. This
museum collection is curated by Gabrielle Delbarre, a co-author on this study, who provided the necessary permissions to sample
these specimens for ancient DNA and radiocarbon dating.
Specimen deposition Residues from aDNA sampling have been returned to the collection at Bournemouth University.
Dating methods New dates were generated at CIRAM, Bordeaux, France and Chronocentre, QUB, UK. Details of each laboratory's protocol are
available from their websites. Dates were calibrated using CALIB 8.2 and the IntCal20 curve.
Tick this box to confirm that the raw and calibrated dates are available in the paper or in Supplementary Information.
Ethics oversight Ethical approval was obtained from the School of Natural Sciences Research Ethics Committee, Trinity College Dublin. All samples are
over 1400 years old and thus have no close genetic relationships to living persons. These specimens do not come from a sensitive
context that has special social or political significance to some people alive today. We followed established ethical guidelines within
the field of ancient DNA. This includes drawing up a detailed research plan prior to initiating the project, minimizing damage to
human remains while sampling and depositing sequence data to a publicly accessible online repository.
Note that full information on the approval of the study protocol must also be provided in the manuscript.
Novel plant genotypes N/A
Seed stocks N/A
Authentication N/A
Plants
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