Review article about Ancient Genomics, by Pontus Skoglund and Iain Mathieson

ancient-genomics-holocene-migrations

A preprint article by two of the most prolific researchers in Human Ancestry is out, and they request feedback: Ancient genomics: a new view into human prehistory and evolution, by Skoglund and Mathieson (2017). Right now, it is downloadable on Dropbox.

Abstract:

The first decade of ancient genomics has revolutionized the study of human prehistory and evolution. We review new insights based on ancient genomic data, including greatly increased resolution of the timing and structure of the out-of-Africa event, the diversification of present-day non-African populations, and the earliest expansions of those populations into Eurasia and America. Prehistoric genomes now document patterns of population continuity and change on every inhabited continent–in particular the effect of agricultural expansions in Africa, Europe and Oceania–and record a history of natural selection that shapes present-day phenotypic diversity. Despite these advances, much remains unknown, in particular about the genomic histories of Asia–the most populous continent, and Africa–the continent that contains the most genetic diversity. Ancient genomes from these and other regions, integrated with a growing understanding of the genomic basis of human phenotypic diversity, will be in focus during the next decade of research in the field.

The paper may be highly recommended as an introduction for anyone interested in the field of Human Ancestry in general.

However, its short summary of steppe ancestry expansion (where the Corded Ware culture predominates) is still reminiscent of the infamous “Yamnaya -> Corded Ware -> Bell Beaker” model set forth by the 2015 Nature articles on the subject, and Kristiansen’s Indo-European Corded Ware theory.

Here is an excerpt (emphasis mine):

The next substantial change is closely related to ancestry that by around 5000 BP extended over a region of more than 2000 miles of the Eurasian steppe, including in individuals associated with the Yamnaya Cultural Complex in far-eastern Europe (1; 38) and with the Afanasievo culture in the central Asian Altai mountains (1). This “steppe” ancestry is itself a mixture between ancestry that is related to Mesolithic hunter-gatherers of eastern Europe and ancestry that is related to both present-day populations (38) and Mesolithic hunter-gatherers (46) from the Caucasus mountains, and also to the populations of Neolithic (11), and Copper Age (56) Iran. Steppe ancestry appeared in southeastern Europe by 6000 BP (72), northeastern Europe around 5000 BP (47) and central Europe at the time of the Corded Ware Complex around 4600 BP (1; 38). These dates are reasonably tight constraints, because in each case there is no evidence of steppe ancestry in individuals immediately preceding these dates (47; 72). Gene flow on the steppe was extensive and bidirectional, as shown by the eastward flow of Anatolian Neolithic ancestry– reaching well into central Eurasia by the time of the Andronovo culture ~3500 BP (1)–and the westward flow of East Asian ancestry–found in individuals associated with the Iron Age Scythian culture close to the Black Sea ~2500 BP (143).

Copper and Bronze Age population movements (14; 78 Martiniano, 2017 #8761; 85; 112), as well as later movements in the Iron Age and Historical period (70; 119) further distributed steppe ancestry around Europe. Present-day western European populations can be modeled as mixtures of these three ancestry components (Mesolithic hunter-gatherer, Anatolian Neolithic and Steppe) (38; 57). In eastern Europe, further shifts in ancestry are the result of additional or distinct gene flow from Anatolia throughout the Neolithic and Bronze Age in the Aegean (42; 51; 55; 72; 87), and gene flow from Siberian-related populations in Finland and the Baltic region (38). East-west gene flow also brought new ancestry–related to populations from 265 Copper Age Iran–to the Levant during the Copper and Bronze ages (39; 56).

The geographic structure of these population transformations gave rise to population structure of present-day Europe. For example Anatolian Neolithic ancestry is highest in southern European populations like Sardinians, and lowest in northern European populations (38). Steppe ancestry is at high frequency in north-central Europeans and low in the south. Isolation-by-distance may have contributed to these patterns to some extent, but the contribution must have been small. In much of Europe, extreme population discontinuity was the norm.

Featured image: from the article, “Major Holocene population movements and expansions that have been demonstrated using ancient DNA.”

Related:

Holocene rise in mobility in at least three stages: Strong link between technological change and human mobility in Western Eurasia

estimating-mobility

New interesting article at PNAS: Estimating mobility using sparse data: Application to human genetic variation, by Loog et al (2017).

Download links and supplemental information.

Significance

Migratory activity is a critical factor in shaping processes of biological and cultural change through time. We introduce a method to estimate changes in underlying migratory activity that can be applied to genetic, morphological, or cultural data and is well-suited to samples that are sparsely distributed in space and through time. By applying this method to ancient genome data, we infer a number of changes in human mobility in Western Eurasia, including higher mobility in pre- than post-Last Glacial Maximum hunter–gatherers, and oscillations in Holocene mobility with peaks centering on the Neolithic transition and the beginnings of the Bronze Age and the Late Iron Age.

Abstract

Mobility is one of the most important processes shaping spatiotemporal patterns of variation in genetic, morphological, and cultural traits. However, current approaches for inferring past migration episodes in the fields of archaeology and population genetics lack either temporal resolution or formal quantification of the underlying mobility, are poorly suited to spatially and temporally sparsely sampled data, and permit only limited systematic comparison between different time periods or geographic regions. Here we present an estimator of past mobility that addresses these issues by explicitly linking trait differentiation in space and time. We demonstrate the efficacy of this estimator using spatiotemporally explicit simulations and apply it to a large set of ancient genomic data from Western Eurasia. We identify a sequence of changes in human mobility from the Late Pleistocene to the Iron Age. We find that mobility among European Holocene farmers was significantly higher than among European hunter–gatherers both pre- and postdating the Last Glacial Maximum. We also infer that this Holocene rise in mobility occurred in at least three distinct stages: the first centering on the well-known population expansion at the beginning of the Neolithic, and the second and third centering on the beginning of the Bronze Age and the late Iron Age, respectively. These findings suggest a strong link between technological change and human mobility in Holocene Western Eurasia and demonstrate the utility of this framework for exploring changes in mobility through space and time.

Featured image, from the article: Estimation of mobility through time from empirical data. (A) Relative mobility rate estimates in Western Eurasia over the last 14,000 y, using a 4,000-y sliding window (121 windows). The solid black line represents the mean α value from 10,000 date resampled iterations; the colored area represents the 95% confidence intervals of the jackknife distribution.

Iberian Peninsula: Discontinuity in mtDNA between hunter-gatherers and farmers, not so much during the Chalcolithic and EBA

iberia-mtdna

A new preprint paper at BioRxiv, The maternal genetic make-up of the Iberian Peninsula between the Neolithic and the Early Bronze Age, by Szécsényi-Nagy et al. (2017).

Abstract:

Agriculture first reached the Iberian Peninsula around 5700 BCE. However, little is known about the genetic structure and changes of prehistoric populations in different geographic areas of Iberia. In our study, we focused on the maternal genetic makeup of the Neolithic (~ 5500-3000 BCE), Chalcolithic (~ 3000-2200 BCE) and Early Bronze Age (~ 2200-1500 BCE). We report ancient mitochondrial DNA results of 213 individuals (151 HVS-I sequences) from the northeast, central, southeast and southwest regions and thus on the largest archaeogenetic dataset from the Peninsula to date. Similar to other parts of Europe, we observe a discontinuity between hunter-gatherers and the first farmers of the Neolithic. During the subsequent periods, we detect regional continuity of Early Neolithic lineages across Iberia, however the genetic contribution of hunter-gatherers is generally higher than in other parts of Europe and varies regionally. In contrast to ancient DNA findings from Central Europe, we do not observe a major turnover in the mtDNA record of the Iberian Late Chalcolithic and Early Bronze Age, suggesting that the population history of the Iberian Peninsula is distinct in character.

iberian-mtdna-samples
Iberian mtDNA samples

Detailed conclusions of their work,

The present study, based on 213 new and 125 published mtDNA data of prehistoric Iberian individuals suggests a more complex mode of interaction between local hunter-gatherers and incoming early farmers during the Early and Middle Neolithic of the Iberian Peninsula, as compared to Central Europe. A characteristic of Iberian population dynamics is the proportion of autochthonous hunter-gatherer haplogroups, which increased in relation to the distance to the Mediterranean coast. In contrast, the early farmers in Central Europe showed comparatively little admixture of contemporaneous hunter-gatherer groups. Already during the first centuries of Neolithic transition in Iberia, we observe a mix of female DNA lineages of different origins. Earlier hunter-gatherer haplogroups were found together with a variety of new lineages, which ultimately derive from Near Eastern farming groups. On the other hand, some early Neolithic sites in northeast Iberia, especially the early group from the cave site of Els Trocs in the central Pyrenees, seem to exhibit affinities to Central European LBK communities. The diversity of female lineages in the Iberian communities continued even during the Chalcolithic, when populations became more homogeneous, indicating higher mobility and admixture across different geographic regions. Even though the sample size available for Early Bronze Age populations is still limited, especially with regards to El Argar groups, we observe no significant changes to the mitochondrial DNA pool until the end of our time transect (1500 BCE). The expansion of groups from the eastern steppe, which profoundly impacted Late Neolithic and EBA groups of Central and North Europe, cannot (yet) be seen in the contemporaneous population substrate of the Iberian Peninsula at the present level of genetic resolution. This highlights the distinct character of the Neolithic transition both in the Iberian Peninsula and elsewhere and emphasizes the need for further in depth archaeogenetic studies for reconstructing the close reciprocal relationship of genetic and cultural processes on the population level.

So it seems more and more likely that the North-West Indo-European invasion during the Copper Age (signaled by changes in Y-DNA lineages) was not, as in central Europe, accompanied by much mtDNA turnover. What that means – either a male-dominated invasion, or a longer internal evolution of invasive Y-DNA subclades – remains to bee seen, but I am still more inclined to see the former as the most likely interpretation, in spite of admixture results.

Related:

Featured images: from the article, licensed BY-NC-ND.

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/.

Neolithic and Bronze Age Basque-speaking Iberians resisted invaders from the steppe

gaul-asterix

Good clickbait, right? I have received reports about this new paper in Google Now the whole weekend, and their descriptions are getting worse each day.

The original title of the article published in PLOS Genetics (already known by its preprint in BioRxiv) was The population genomics of archaeological transition in west Iberia: Investigation of ancient substructure using imputation and haplotype-based methods, by Martiniano et al. (2017).

Maybe the title was not attractive enough, so they sent the following summary, entitled “Bronze Age Iberia received fewer Steppe invaders than the rest of Europe” (also in Phys.org. From their article, the only short reference to the linguistic situation of Iberia (as a trial to sum up potential consequences of the genetic data obtained):

Iberia is unusual in harbouring a surviving pre-Indo-European language, Euskera, and inscription evidence at the dawn of history suggests that pre-Indo-European speech prevailed over a majority of its eastern territory with Celtic-related language emerging in the west. Our results showing that predominantly Anatolian-derived ancestry in the Neolithic extended to the Atlantic edge strengthen the suggestion that Euskara is unlikely to be a Mesolithic remnant. Also our observed definite, but limited, Bronze Age influx resonates with the incomplete Indo-European linguistic conversion on the peninsula, although there are subsequent genetic changes in Iberia and defining a horizon for language shift is not yet possible. This contrasts with northern Europe which both lacks evidence for earlier language strata and experienced a more profound Bronze Age migration.

Judging from the article, more precise summaries of potential consequences would have been “Proto-Basque and Proto-Iberian peoples derived from Neolithic farmers, not Mesolithic or Palaeolithic hunter-gatherers”, or “incomplete Indo-European linguistic conversion of the Iberian Peninsula” – both aspects, by the way, are already known. That would have been quite unromantic, though.

Their carefully selected title has been unsurprisingly distorted at least as “Ancient DNA Reveals Why the Iberian Peninsula Is So Unique“, and “Ancient Iberians resisted Steppe invasions better than the rest of Europe 6,000 years ago“.

So I thought, what the hell, let’s go with the tide. Using the published dataset, I have also helped reconstruct the original phenotype of Bronze Age Iberians, and this is how our Iberian ancestors probably looked like:

Typical Iberian village during the Steppe invasion, according to my phenotype study of Martiniano et al. (2017). Notice typical invaders to the right.

And, by the way, they spoke Basque, the oldest language. Period.

Now, for those new to the article, we already knew that there is less “steppe admixture” in Iberian samples from southern Portugal after the time of east Bell Beaker expansion.

portugal-bronze-age-admixture
(A) PCA estimated from the CHROMOPAINTER coancestry matrix of 67 ancient samples ranging from the Paleolithic to the Anglo-Saxon period. The samples belonging to each one of the 19 populations identified with fineSTRUCTURE are connected by a dashed line. Samples are placed geographically in 3 panels (with random jitter for visual purposes): (B) Hunter-gatherers; (C) Neolithic Farmers (including Ötzi) and (D) Copper Age to Anglo-Saxon samples. The Portuguese Bronze Age samples (D, labelled in red) formed a distinct population (Portuguese_BronzeAge), while the Middle and Late Neolithic samples from Portugal clustered with Spanish, Irish and Scandinavian Neolithic farmers, which are termed “Atlantic_Neolithic” (C, in green).

However, there is also a clear a discontinuity in Neolithic Y-DNA haplogroups (to R1b-P312 haplogroups). That means obviously a male-driven invasion, from the North-West Indo-European-speaking Bell Beaker culture – which in turn did not have much “steppe admixture” compared to other north-eastern cultures, like the Corded Ware culture, probably unrelated to Indo-European languages.

portugal-bronze-age-haplogroup
Summary of the samples sequenced in the present study.

As always, trying to equate steppe or Yamna admixture with invasion or language is plainly wrong. Doing it with few samples, and with the wrong assumptions of what “steppe admixture” means, well…

Proto-Basque and Proto-Iberian no doubt survived the Indo-European Bell Beaker migrations, but if Y-DNA lineages were replaced already by the Bronze Age in southern Portugal, there is little reason to support an increased “resistance” of Iberians to Bell Beaker invaders compared to other marginal regions of Europe (relative to the core Yamna expansion in eastern and central Europe).

As you know, Aquitanian (the likely ancestor of Basque) and Iberian were just two of the many non-Indo-European languages spoken in Europe at the dawn of historical records, so to speak about Iberia as radically different than Italy, Greece, Northern Britain, Scandinavia, or Eastern Europe, is reminiscent of the racism (or, more exactly, xenophobia) that is hidden behind romantic views certain people have of their genetic ancestry.

Some groups formed by a majority of R1b-DF27 lineages, now prevalent in Iberia, spoke probably Iberian languages during the Iron Age in north and eastern Iberia, before their acculturation during the expansion of Celtic-speaking peoples, and later during the expansion of Rome, when most of them eventually spoke Latin. In Mediaeval times, these lineages probably expanded Romance languages southward during the Reconquista.

Before speaking Iberian languages, R1b-DF27 lineages (or older R1b-P312) were probably Indo-European speakers who expanded with the Bell Beaker culture from the lower Danube – in turn created by the interaction of Yamna with Proto-Bell Beaker cultures, and adopted probably the native Proto-Basque and Proto-Iberian languages (or possibly the ancestor of both) near the Pyrenees, either by acculturation, or because some elite invaders expanded successfully (their Y-DNA haplogroup) over the general population, for generations.

Maybe some kind of genetic bottleneck happened, that expanded previously not widespread lineages, as with N1c subclades in Finland.

There is nothing wrong with hypothetic models of ancient genetic prehistory: there are still too many potential scenarios for the expansion of haplogroup R1b-DF27 in Iberia. But, please, stop supporting romantic pictures of ethnolinguistic continuity for modern populations. It’s embarrassing.


Featured image from Wikipedia, and Pinterest, with copyright from Albert Uderzo and publisher company Hachette.

Images from the article, licensed CC-by-sa, as all articles from PLOS.

Heyd, Mallory, and Prescott were right about Bell Beakers

yamna-migration

Sometimes it is fun to read certain “old” papers. I have recently re-read some important papers that predicted what we are seeing now in aDNA analysis with surprising accuracy:

Harrison & Heyd (2007): “We predict that future stable isotope and ancientDNA analyses of Beaker skeletal material will support our view that immigration played an important role in the Europe-wide Bell Beaker phenomenon”. – Duh, obvious, right? Wrong. Read the whole paper. It was already becoming a classic in the study of the Bell Beaker culture before the latest research on Bell Beaker aDNA, and it will be still more important from now on. There are different models for the Bell Beaker origin and expansion, and this was only one of them: we had the Dutch model, the radiocarbon date-based attempts to locate Bell Beakers in Iberia or North Africa,… I tried to highlight the best sentences from Heyd’s article to include them in my article, and I just couldn’t stop highlighting almost everything. It is surprising that 10 years ago Volker Heyd was predicting so much from such a limited amount of material, and with conflicting reports coming from everywhere, from palaeogenetics to radiocarbon dating. Not that today their chronology of Le Petit – Chasseur is accepted by all, but their general Bell Beaker and Yamna model has been clearly established as the most likely one with support from aDNA.

– Mallory in Celtic from the West 2 (2013), as the last of many to propose Bell Beaker as the vector of spread of Late Indo-European languages, but the first to relate it to North-West Indo-European: “The spread of Indo-European languages from Alpine Europe may have begun with the Beaker culture, presuming here a non-Iberian Beaker homeland (Rhineland, Central European) for that part of the Beaker phenomenon that was associated with an Indo-European language. While it is possible that IE language(s) spread with the Beaker phenomenon, it is questionable that this was associated with Proto-Celtic rather than earlier forms of Late Indo-European, at least part of which might be subsumed under the heading NW Indo-European. This is because the time depth of the dispersal of the Beakers is so great and the earliest attested Celtic languages are so similar (…)”. You might think that it is related to the Atlantic Indo-European theory favoured by Cunnliffe and Koch in the book… Wrong, he specifically dismisses a Neolithic spread of Indo-European, and a Calcholithic spread of Celtic languages as too early. You might also think that to publish that in 2013 has no merit, given the data. Wrong again. Just look at the trend among renown archaeologists – like Anthony (with Haak) and Kristiansen (with Allentoft) – trying to hop on the bandwagon of Corded Ware-driven Indo-European dispersal based on the “steppe admixture” proportion of recent genetic papers, and you realize he is going against the grain here.

Prescott and Walderhaug 1995 (as referred to in Prescott 2012): “The Bell Beaker period is the most, perhaps the only, reasonable candidate for the spread and final entrenchment of a common Indo-European language throughout Scandinavia (and not just Corded Ware core areas of southern and eastern Scandinavia), and particularly Norway”. Duh again? Not so fast. While Bell Beaker had been proposed before as a vector of Indo-European languages in Europe, the association with Germanic was far more controversial. Only the unifying Dagger Period was more clearly established as of Pre-Germanic nature, but it could be interpreted as of Corded Ware, Úněticean, or even early Neolithic origin, or a mix of them. Bell Beaker groups were never good candidates, if only because of the desire by some researchers to offer a romanticized (either more unifying or ancient) picture of a Germanic Northern Scandinavian homeland, explained as a culturally and genetically homogeneous group.

Their papers seem to state the obvious now that the latest aDNA samples are proving them correct, but it was far from clear years ago: remember the native European Basque-R1b – Uralic-N1c harmony disrupted by invasive Eurasian Indo-European-speaking warriors carrying R1a lineages from Yamna to Corded Ware? Well that is still a thing for some. And even today the most popular interpretation of the spread of Indo-European-speakers in Europe is based on the defined “steppe ancestry” proportion found in Corded Ware individuals, and a supposedly Yamna community formed by R1b-R1a lineages, which is obviously reminiscent of the identification of R1a lineages with Proto-Indo-Europeans based on the initial analysis of haplogroups in modern populations.

It is sad to imagine how much we would have improved in our knowledge, had we read their work with interest when it was necessary, and not now that we have most of the aDNA clues. Still sadder is to see people rely on genetic studies alone to derive today what are likely the wrong conclusions. Again.

I will end with a mea culpa. I hadn’t read those works; but even if I had, I would have stayed with the simpler, R1a-Corded Ware model of Indo-European dispersion. That oversimplification will remain in the different editions of our Grammar of Modern Indo-European as a permanent reminder. Simpler seems always better, and Cavalli-Sforza had famously asserted that ancient population movements could be solved with the study of the structure of modern populations. I think he was right, that we can in fact ascertain ancient population movements by studying modern populations if we include anthropological disciplines, but it is such a complex task – and geneticists have not shown a good grasp in (or interest for) Anthropology -, that it is nowadays clearly wrong to rely on modern population samples to derive conclusions about ancient populations, and we are better off studying ancient DNA samples in their context.

We were Back-to-the-Future-wrong, overestimating our potential in some aspects – like the results of researching modern DNA -, and underestimating it in others – like the potential changes that ancient DNA investigation could bring for anthropological disciplines. Just as we are wrong today in trusting the potential of admixture analysis to be self-explanatory, without a need for wide anthropological investigation (or even able to revolutionize archaeological and linguistic theories).

I hope to keep a more critical view of publications – especially the most popular ones – from now on.