More Celts of hg. R1b, more Afanasievo ancestry, more maps

iron-age-early-celtic-expansion

Interesting recent developments:

Celts and hg. R1b

Gauls

Recent paper (behind paywall) Multi-scale archaeogenetic study of two French Iron Age communities: From internal social- to broad-scale population dynamics, by Fischer et al. J Archaeol Sci (2019).

In it, Fischer and colleagues update their previous data for the Y-DNA of Gauls from the Urville-Nacqueville necropolis, Normandy (ca. 300-100 BC), with 8 samples of hg. R, at least 5 of them R1b. They also report new data from the Gallic cemetery at Gurgy ‘Les Noisats’, Southern Paris Basin (ca. 120-80 BC), with 19 samples of hg. R, at least 13 of them R1b.

In both cases, it is likely that both communities belonged (each) to the same paternal lineages, hence the patrilocal residence rules and patrilineality described for Gallic groups, also supported by the different maternal gene pools.

The interesting data would be whether these individuals were of hg. R1b-L21, hence mainly local lineages later replaced or displaced to the west, or – a priori much more likely – of some R1b-U152 and/or R1b-DF27 subclades from Central Europe that became less and less prevalent as Celts expanded into more isolated regions south of the Pyrenees and into the British Isles. Such information is lacking in the paper, probably due to the poor coverage of the samples.

early-iron-age-europe-y-dna
Y-DNA haplogroups in Europe during the Early Iron Age. See full map.

Other Celts

As for early Celts, we already have:

Celtiberians from the Basque Country (one of hg. I2a) and likely Celtic genetic influence in north-east Iberia (all R1b), where Iberian languages spread later, showing that Celts expanded from some place in Central Europe, probably already with the Urnfield culture (ca. 1300 BC on).

Two Hallstatt samples from Bylany, Bohemia (ca. 836-780 BC), by Damgaard et al. Nature (2018), one of them of hg. R1b-U152.

mitterkirchen-grab-hu-i-8-hallstatt
Photo and diagram of burial HÜ-I/8, Mitterkirchen, Oberösterreich, Leskovar 1998.

Another Hallstatt HaC/D1 sample from Mittelkirchen, Austria (ca. 850-650/600), by Kiesslich et al. (2012), with predicted hg. G2a (see Athey’s haplogroup prediction).

One sample of early La Tène culture A from Putzenfeld am Dürrnberg, Hallein, Austria (ca 450–380 BC), by Kiesslich et al. (2012), with predicted hg. R1b (see Athey’s haplogroup prediction).

NOTE. For potential unreliability of haplogroup prediction with Whit Atheys’ haplogroup predictor, see e.g. Zhang et al. (2017).

kelten-dna-putzenfeld-duerrnberg-grab-376
Photo and diagram of Burial 376, Putzenfeld, Dürrnberg bei Hallein, Moser 2007.

Three Britons from Hinxton, South Cambridgeshire (ca. 170 BC – AD 80) from Schiffels et al. (2016), two of them of local hg. R1b-S461.

Indirectly, data of Vikings by Margaryan et al. (2019) from the British Isles and beyond show hg. R1b associated with modern British-like ancestry, also linked to early “Picts”, hence likely associated with Britons even after the Anglo-Saxon settlement. Supporting both (1) my recent prediction of hg. R1b-M167 expanding with Celts and (2) the reason for its presence among modern Scandinavians, is the finding of the first ancient sample of this subclade (VK166) among the Vikings of St John’s College Oxford, associated with the ‘St Brice’s Day Massacre’ (see Margaryan et al. 2019 supplementary materials).

The R1b-M167 sample shows 23.5% British-like ancestry, hence autosomally closer to other local samples (and related to the likely Picts from Orkney) than to some of his deceased partners at the site. Other samples with sizeable British-like ancestry include VK177 (32.6%, hg. R1b-U152), VK173 (33.3%, hg. I2a1b1a), or VK150 (25.6%, hg. I2a1b1a), while typical Germanic subclades like I1 or R1b-U106 – which may be associated with Anglo-Saxons, too – tend to show less.

late-iron-age-europe-y-dna
Y-DNA haplogroups in Europe during the Late Iron Age. See full map.

I remember some commenter asking recently what would happen to the theory of Proto-Indo-European-speaking R1b-rich Yamnaya culture if Celts expanded with hg. R1a, because there were only one hg. R1b and one (possibly) G2a from Hallstatt. As it turns out, they were mostly R1b. However, the increasingly frequent obsession of searching for specific haplogroups and ancestry during the Iron Age and the Middle Ages is weird, even as a desperate attempt, because:

  1. it is evident that the more recent the ancient DNA samples are, the more they are going to resemble modern populations of the same area, so ancient DNA would become essentially useless;
  2. cultures from the early Iron Age onward (and even earlier) were based on increasingly complex sociopolitical systems everywhere, which is reflected in haplogroup and ancestry variability, e.g. among Balts, East Germanic peoples, Slavs (of hg. E1b-V13, I2a-L621), or Tocharians.

In fact, even the finding of hg. R1b among Celts of central and western Europe during the Iron Age is rather unenlightening, because more specific subclades and information on ancestry changes are needed to reach any meaningful conclusion as to migration vs. acculturation waves of expanding Celtic languages, which spread into areas that were mostly Indo-European-speaking since the Bell Beaker expansion.

Afanasevo ancestry in Asia

Wang and colleagues continue to publish interesting analyses, now in the preprint Inland-coastal bifurcation of southern East Asians revealed by Hmong-Mien genomic history, by Xia et al. bioRxiv (2019).

Interesting excerpt (emphasis mine):

Although the Devil’s Cave ancestry is generally the predominant East Asian lineage in North Asia and adjacent areas, there is an intriguing discrepancy between the eastern [Korean, Japanese, Tungusic (except northernmost Oroqen), and Mongolic (except westernmost Kalmyk) speakers] and the western part [West Xiōngnú (~2,150 BP), Tiānshān Hun (~1,500 BP), Turkic-speaking Karakhanid (~1,000 BP) and Tuva, and Kalmyk]. Whereas the East Asian ancestry of populations in the western part has entirely belonged to the Devil’s Cave lineage till now, populations in the eastern part have received the genomic influence from an Amis-related lineage (17.4–52.1%) posterior to the presence of the Devil’s Cave population roughly in the same region (~7,600 BP)12. Analogically, archaeological record has documented the transmission of wet-rice cultivation from coastal China (Shāndōng and/or Liáoníng Peninsula) to Northeast Asia, notably the Korean Peninsula (Mumun pottery period, since ~3,500 BP) and the Japanese archipelago (Yayoi period, since ~2,900 BP)2. Especially for Japanese, the Austronesian-related linguistic influence in Japanese may indicate a potential contact between the Proto-Japonic speakers and population(s) affiliating to the coastal lineage. Thus, our results imply that a southern-East-Asian-related lineage could be arguably associated with the dispersal of wet-rice agriculture in Northeast Asia at least to some extent.

afanasevo-namazga-devils-gate-xiongnu-huns-tianshan-admixture
Spatial and temporal distribution of ancestries in East Asians. Reference populations and corresponding hypothesized ancestral populations: (1) Devil’s Cave (~7,600 BP), the northern East Asian lineage; (2) Amis, the southern East Asian lineage (= AHM + AAA + AAN); (3) Hòabìnhian (~7,900 BP), a lineage related to Andamanese and indigenous hunter-gatherer of MSEA; (4) Kolyma (~9,800 BP), “Ancient Palaeo-Siberians”; (5) Afanasievo (~4,800 BP), steppe ancestry; (6) Namazga (~5,200 BP), the lineage of Chalcolithic Central Asian. Here, we report the best-fitting results of qpAdm based on following criteria: (1) a feasible p-value (&mt; 0.05), (2) feasible proportions of all the ancestral components (mean &mt; 0 and standard error < mean), and (3) with the highest p-value if meeting previous conditions.

In this case, the study doesn’t compare Steppe_MLBA, though, so the findings of Afanasievo ancestry have to be taken with a pinch of salt. They are, however, compared to Namazga, so “Steppe ancestry” is there. Taking into account the limited amount of Yamnaya-like ancestry that could have reached the Tian Shan area with the Srubna-Andronovo horizon in the Iron Age (see here), and the amount of Yamnaya-like ancestry that appears in some of these populations, it seems unlikely that this amount of “Steppe ancestry” would emerge as based only on Steppe_MLBA, hence the most likely contacts of Turkic peoples with populations of both Afanasievo (first) and Corded Ware-derived ancestry (later) to the west of Lake Baikal.

(1) The simplification of ancestral components into A vs. B vs. C… (when many were already mixed), and (2) the simplistic selection of one OR the other in the preferred models (such as those published for Yamnaya or Corded Ware), both common strategies in population genomics pose evident problems when assessing the actual gene flow from some populations into others.

Also, it seems that when the “Steppe”-like contribution is small, both Yamnaya and Corded Ware ancestry will be good fits in admixed populations of Central Asia, due to the presence of peoples of EHG-like (viz. West Siberia HG) and/or CHG-like (viz. Namazga) ancestry in the area. Unless and until these problems are addressed, there is little that can be confidently said about the history of Yamnaya vs. Corded Ware admixture among Asian peoples.

Maps, maps, and more maps

As you have probably noticed if you follow this blog regularly, I have been experimenting with GIS software in the past month or so, trying to map haplogroups and ancestry components (see examples for Vikings, Corded Ware, and Yamnaya). My idea was to show the (pre)historical evolution of ancestry and haplogroups coupled with the atlas of prehistoric migrations, but I have to understand first what I can do with GIS statistical tools.

My latest exercise has been to map modern haplogroup distribution (now added to the main menu above) using data from the latest available reports. While there have been no great surprises – beyond the sometimes awful display of data by some papers – I think it is becoming clearer with each new publication how wrong it was for geneticists to target initially those populations considered “isolated” – hence subject to strong founder effects – to extrapolate language relationships. For example:

  • The mapping of R1b-M269, in particular basal subclades, corresponds nicely with the Indo-European expansions.
  • There is no clear relationship of R1b, not even R1b-DF27 (especially basal subclades), with Basques. There is no apparent relationship between the distribution of R1b-M269 and some mythical non-Indo-European “Old Europeans”, like Etruscans or Caucasian speakers, either.
  • Basal R1a-M417 shows an interesting distribution, as do maps of basal Z282 and Z93 subclades, despite the evident late bottlenecks and acculturation among Slavs.
  • The distribution of hg. N1a-VL29 (and other N1a-L392 subclades) is clearly dissociated from Uralic peoples, and their expansion in the whole Baltic Sea during the Iron Age doesn’t seem to be related to any specific linguistic expansion.
  • haplogroup-n1a-vl29
    Modern distribution of haplogroup N1a-VL29. See full map.
  • Even the most recent association in Post et al. (2019) with hg. N1a-Z1639 – due to the lack of relationship of Uralic with N1a-VL29 – seems like a stretch, seeing how it probably expanded from the Kola Peninsula and the East Urals, and neither the Lovozero Ware nor forest hunter-fishers of the Cis- and Trans-Urals regions were Uralic-speaking cultures.
  • The current prevalence of hg. R1b-M73 supports its likely expansion with Turkic-speaking peoples.
  • The distribution of haplogroup R1b-V88 in Africa doesn’t look like it was a mere founder effect in Chadic peoples – although they certainly underwent a bottleneck under it.
  • The distribution of R1a-M420 (xM198) and hg. R1b-M343 (possibly not fully depicted in the east) seem to be related to expansions close to the Caucasus, supporting once more their location in Eastern Europe / West Siberia during the Mesolithic.
  • The mapping of E1b-V13 and I-M170 (I haven’t yet divided it into subclades) are particularly relevant for the recent eastward expansion of early Slavic peoples.

All in all, modern haplogroup distribution might have been used to ascertain prehistoric language movements even in the 2000s. It was the obsession with (and the wrong assumptions about) the “purity” of certain populations – say, Basques or Finns – what caused many of the interpretation problems and circular reasoning we are still seeing today.

I have also updated maps of Y-chromosome haplogroups reported for ancient samples in Europe and/or West Eurasia for the Early Eneolithic, Early Chalcolithic, Late Chalcolithic, Early Bronze Age, Middle Bronze Age, Late Bronze Age, Early Iron Age, Late Iron Age, Antiquity, and Middle Ages.

Haplogroup inference

I have also tried Yleaf v.2 – which seems like an improvement over the infamous v.1 – to test some samples that hobbyists and/or geneticists have reported differently in the past. I have posted the results in this ancient DNA haplogroup page. It doesn’t mean that the inferences I obtain are the correct ones, but now you have yet another source to compare.

Not many surprises here, either:

  • M15-1 and M012, two Proto-Tocharians from Shirenzigou, are of hg. R1b-PH155, not R1b-M269.
  • I0124, the Samara HG, is of hg. R1b-P297, but uncertain for both R1b-M73 and R1b-M269.
  • I0122, the Khvalynsk chieftain, is of hg. R1b-V1636.
  • I2181, the Smyadovo outlier of poor coverage, is possibly of hg. R, and could be of hg. R1b-M269, but could also be even non-P.
  • I6561 from Alexandria is probably of hg. R1a-M417, likely R1a-Z645, maybe R1a-Z93, but can’t be known beyond that, which is more in line with the TMRCA of R1a subclades and the radiocarbon date of the sample.
  • I2181, the Yamnaya individual (supposedly Pre-R1b-L51) at Lopatino II is R1b-M269, negative for R1b-L51. Nothing beyond that.

You can ask me to try mapping more data or to test the haplogroup of more samples, provided you give me a proper link to the relevant data, they are interesting for the subject of this blog…and I have the time to do it.

Related

First Iberian R1b-DF27 sample, probably from incoming East Bell Beakers

bronze_age_iberia

I had some more time to read the paper by Valdiosera et al. (2018) and its supplementary material.

One of the main issues since the publication of Olalde et al. (2018) (and its hundreds of Bell Beaker samples) was the lack of a clear Y-DNA R1b-DF27 subclades among East Bell Beaker migrants, which left us wondering when the subclade entered the Iberian Peninsula, since it could have (theoretically) happened from the Chalcolithic to the Iron Age.

My prediction was that this lineage found today widespread among the Iberian population crossed the Pyrenees quite early, during the Chalcolithic, with migrating East Bell Beakers expanding North-West Indo-European dialects, and that it spread slowly afterwards.

The first ancient sample clearly identified as of R1b-DF27 subclade is found in this paper, at the Late Bronze Age site Cueva de los Lagos. Although it is unidentified and has no radiocarbon date, the site as a whole is associated with the Cogotas culture and its Bouquique ceramic decoration.

iberia-y-dna-mtdna
Y-DNA and mtDNA haplogroups, from the paper. Sequencing statistics and contamination rates for newly generated sequence data.

It was found in the northern part of the Cogotas culture territory (which lies mainly between Castille and Aragon, in North-Central Spain), shows evident steppe admixture, and it has become obvious with the latest papers (including this one) that R1b-M269 lineages intruded south of the Pyrenees associated with East Bell Beaker migrations.

The Proto-Cogotas culture is associated with a Bell Beaker substrate influenced by either El Argar or Atlantic Bronze, and the specific type of ceramics found at this Cogotas culture site are probably from the mid-2nd millennium, which is too early for the Celtic expansion.

iberia-steppe-admixture
Supervised ADMIXTURE results.

Nevertheless, due to the quite likely late date of the sample (in the centuries around 1500 BC), there is still a possibility that incoming R1b-DF27 lineages were not among the early R1b-M269 lineages found in the Iberian Chalcolithic, and were associated with later migrations from Central Europe, potentially linked to the expansion of the Urnfield culture, and thus nearer to an Italo-Celtic community.

bronze-age-tollense
Diachronic map of migrations in Europe ca. 1250-750 BC.

In any of these scenarios, a Pre-Celtic expansion of North-West Indo-European in Iberia (possibly associated with Lusitanian) is still the best explanation for the origin and expansion of (at least some) modern Iberian R1b-DF27 lineages, including those found among the Basque-speaking population.

This implies that the ‘indigenous’ Neolithic lineages of Iberia (like I2 and G2a2) were replaced with subsequent internal gene flows and founder effects, such as those that evidently happened (probably quite recently) among Basques, even though indigenous languages show an obvious continuity.

I would say this is the last nail in the coffin for autochthonous Y-DNA continuity theories for Spain and France (i.e. for the traditional Vasconic-Uralic hypothesis), but we know that data is never enough for any die hard continuist…so let’s just say another nail in the coffin for endless autochthonous continuity theories.

EDIT (18 & 26 MAR 2018): Genetiker has published Y-SNP calls for both R1b samples, showing this one is R1b1a1a2a1a2a-BY15964 (see modern members of this subclade in ytree), and that the other one is R1b1a1a2a~L23.

Related:

Analysis of R1b-DF27 haplogroups in modern populations adds new information that contrasts with ‘steppe admixture’ results

R1b-DF27-iberia

New open access article published in Scientific Reports, Analysis of the R1b-DF27 haplogroup shows that a large fraction of Iberian Y-chromosome lineages originated recently in situ, by Solé-Morata et al. (2017).

Abstract

Haplogroup R1b-M269 comprises most Western European Y chromosomes; of its main branches, R1b-DF27 is by far the least known, and it appears to be highly prevalent only in Iberia. We have genotyped 1072 R1b-DF27 chromosomes for six additional SNPs and 17 Y-STRs in population samples from Spain, Portugal and France in order to further characterize this lineage and, in particular, to ascertain the time and place where it originated, as well as its subsequent dynamics. We found that R1b-DF27 is present in frequencies ~40% in Iberian populations and up to 70% in Basques, but it drops quickly to 6–20% in France. Overall, the age of R1b-DF27 is estimated at ~4,200 years ago, at the transition between the Neolithic and the Bronze Age, when the Y chromosome landscape of W Europe was thoroughly remodeled. In spite of its high frequency in Basques, Y-STR internal diversity of R1b-DF27 is lower there, and results in more recent age estimates; NE Iberia is the most likely place of origin of DF27. Subhaplogroup frequencies within R1b-DF27 are geographically structured, and show domains that are reminiscent of the pre-Roman Celtic/Iberian division, or of the medieval Christian kingdoms.

Some people like to say that Y-DNA haplogroup analysis, or phylogeography in general, is of no use anymore (especially modern phylogeography), and they are content to see how ‘steppe admixture’ was (or even is) distributed in Europe to draw conclusions about ancient languages and their expansion. With each new paper, we are seeing the advantages of analysing ancient and modern haplogroups in ascertaining population movements.

Quite recently there was a suggestion based on steppe admixture that Basque-speaking Iberians resisted the invasion from the steppe. Observing the results of this article (dates of expansion and demographic data) we see a clear expansion of Y-DNA haplogroups precisely by the time of Bell Beaker expansion from the east. Y-DNA haplogroups of ancient samples from Portugal point exactly to the same conclusion.

The situation of R1b-DF27 in Basques, as I have pointed out elsewhere, is probably then similar to the genetic drift of Finns, mainly of N1c lineages, speaking today a Uralic language that expaned with Corded Ware and R1a subclades.

The recent article on Mycenaean and Minoan genetics also showed that, when it comes to Europe, most of the demographic patterns we see in admixture are reminiscent of the previous situation, only rarely can we see a clear change in admixture (which would mean an important, sudden replacement of the previous population).

Equating the so-called steppe admixture with Indo-European languages is wrong. Period.

The following are excerpts from the article (emphasis is mine):

Dates and expansions

The average STR variance of DF27 and each subhaplogroup is presented in Suppl. Table 2. As expected, internal diversity was higher in the deeper, older branches of the phylogeny. If the same diversity was divided by population, the most salient finding is that native Basques (Table 2) have a lower diversity than other populations, which contrasts with the fact that DF27 is notably more frequent in Basques than elsewhere in Iberia (Suppl. Table 1). Diversity can also be measured as pairwise differences distributions (Fig. 5). The distribution of mean pairwise differences within Z195 sits practically on top of that of DF27; L176.2 and Z220 have similar distributions, as M167 and Z278 have as well; finally, M153 shows the lowest pairwise distribution values. This pattern is likely to reflect the respective ages of the haplogroups, which we have estimated by a modified, weighted version of the ρ statistic (see Methods).

Z195 seems to have appeared almost simultaneously within DF27, since its estimated age is actually older (4570 ± 140 ya). Of the two branches stemming from Z195, L176.2 seems to be slightly younger than Z220 (2960 ± 230 ya vs. 3320 ± 200 ya), although the confidence intervals slightly overlap. M167 is clearly younger, at 2600 ± 250 ya, a similar age to that of Z278 (2740 ± 270 ya). Finally, M153 is estimated to have appeared just 1930 ± 470 ya.

Haplogroup ages can also be estimated within each population, although they should be interpreted with caution (see Discussion). For the whole of DF27, (Table 3), the highest estimate was in Aragon (4530 ± 700 ya), and the lowest in France (3430 ± 520 ya); it was 3930 ± 310 ya in Basques. Z195 was apparently oldest in Catalonia (4580 ± 240 ya), and with France (3450 ± 269 ya) and the Basques (3260 ± 198 ya) having lower estimates. On the contrary, in the Z220 branch, the oldest estimates appear in North-Central Spain (3720 ± 313 ya for Z220, 3420 ± 349 ya for Z278). The Basques always produce lower estimates, even for M153, which is almost absent elsewhere.

R1b-DF27-tree
Simplified phylogenetic tree of the R1b-M269 haplogroup. SNPs in italics were not analyzed in this manuscript.

Demography

The median value for Tstart has been estimated at 103 generations (Table 4), with a 95% highest probability density (HPD) range of 50–287 generations; effective population size increased from 131 (95% HPD: 100–370) to 72,811 (95% HPD: 52,522–95,334). Considering patrilineal generation times of 30–35 years, our results indicate that R1b-DF27 started its expansion ~3,000–3,500 ya, shortly after its TMRCA.

As a reference, we applied the same analysis to the whole of R1b-S116, as well as to other common haplogroups such as G2a, I2, and J2a. Interestingly, all four haplogroups showed clear evidence of an expansion (p > 0.99 in all cases), all of them starting at the same time, ~50 generations ago (Table 4), and with similar estimated initial and final populations. Thus, these four haplogroups point to a common population expansion, even though I2 (TMRCA, weighted ρ, 7,800 ya) and J2a (TMRCA, 5,500 ya) are older than R1b-DF27. It is worth noting that the expansion of these haplogroups happened after the TMRCA of R1b-DF27.

R1b-DF27-PCA
Principal component analysis of STR haplotypes. (a) Colored by subhaplogroup, (b) colored by population. Larger squares represent subhaplogroup or population centroids.

Sum up and discussion

We have characterized the geographical distribution and phylogenetic structure of haplogroup R1b-DF27 in W. Europe, particularly in Iberia, where it reaches its highest frequencies (40–70%). The age of this haplogroup appears clear: with independent samples (our samples vs. the 1000 genome project dataset) and independent methods (variation in 15 STRs vs. whole Y-chromosome sequences), the age of R1b-DF27 is firmly grounded around 4000–4500 ya, which coincides with the population upheaval in W. Europe at the transition between the Neolithic and the Bronze Age. Before this period, R1b-M269 was rare in the ancient DNA record, and during it the current frequencies were rapidly reached. It is also one of the haplogroups (along with its daughter clades, R1b-U106 and R1b-S116) with a sequence structure that shows signs of a population explosion or burst. STR diversity in our dataset is much more compatible with population growth than with stationarity, as shown by the ABC results, but, contrary to other haplogroups such as the whole of R1b-S116, G2a, I2 or J2a, the start of this growth is closer to the TMRCA of the haplogroup. Although the median time for the start of the expansion is older in R1b-DF27 than in other haplogroups, and could suggest the action of a different demographic process, all HPD intervals broadly overlap, and thus, a common demographic history may have affected the whole of the Y chromosome diversity in Iberia. The HPD intervals encompass a broad timeframe, and could reflect the post-Neolithic population expansions from the Bronze Age to the Roman Empire.

While when R1b-DF27 appeared seems clear, where it originated may be more difficult to pinpoint. If we extrapolated directly from haplogroup frequencies, then R1b-DF27 would have originated in the Basque Country; however, for R1b-DF27 and most of its subhaplogroups, internal diversity measures and age estimates are lower in Basques than in any other population. Then, the high frequencies of R1b-DF27 among Basques could be better explained by drift rather than by a local origin (except for the case of M153; see below), which could also have decreased the internal diversity of R1b-DF27 among Basques. An origin of R1b-DF27 outside the Iberian Peninsula could also be contemplated, and could mirror the external origin of R1b-M269, even if it reaches there its highest frequencies. However, the search for an external origin would be limited to France and Great Britain; R1b-DF27 seems to be rare or absent elsewhere: Y-STR data are available only for France, and point to a lower diversity and more recent ages than in Iberia (Table 3). Unlike in Basques, drift in a traditionally closed population seems an unlikely explanation for this pattern, and therefore, it does not seem probable that R1b-DF27 originated in France. Then, a local origin in Iberia seems the most plausible hypothesis. Within Iberia, Aragon shows the highest diversity and age estimates for R1b-DF27, Z195, and the L176.2 branch, although, given the small sample size, any conclusion should be taken cautiously. On the contrary, Z220 and Z278 are estimated to be older in North Central Spain (N Castile, Cantabria and Asturias). Finally, M153 is almost restricted to the Basque Country: it is rarely present at frequencies >1% elsewhere in Spain (although see the cases of Alacant, Andalusia and Madrid, Suppl. Table 1), and it was found at higher frequencies (10–17%) in several Basque regions; a local origin seems plausible, but, given the scarcity of M153 chromosomes outside of the Basque Country, the diversity and age values cannot be compared.

Within its range, R1b-DF27 shows same geographical differentiation: Western Iberia (particularly, Asturias and Portugal), with low frequencies of R1b-Z195 derived chromosomes and relatively high values of R1b-DF27* (xZ195); North Central Spain is characterized by relatively high frequencies of the Z220 branch compared to the L176.2 branch; the latter is more abundant in Eastern Iberia. Taken together, these observations seem to match the East-West patterning that has occurred at least twice in the history of Iberia: i) in pre-Roman times, with Celtic-speaking peoples occupying the center and west of the Iberian Peninsula, while the non-Indoeuropean eponymous Iberians settled the Mediterranean coast and hinterland; and ii) in the Middle Ages, when Christian kingdoms in the North expanded gradually southwards and occupied territories held by Muslim fiefs.

DF27-iberia-france
Contour maps of the derived allele frequencies of the SNPs analyzed in this manuscript. Population abbreviations as in Table 1. Maps were drawn with SURFER v. 12 (Golden Software, Golden CO, USA).

I wouldn’t trust the absence of R1b-DF27 outside France as a proof that its origin must be in Western Europe – especially since we have ancient DNA, and that assertion might prove quite wrong – but aside from that the article seems solid in its analysis of modern populations.

Related:

Text and figures from the article, licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.