Something is very wrong with models based on the so-called ‘Yamnaya admixture’ – and archaeologists are catching up (II)

A new article by Leo S. Klejn tries to improve the Northern Mesolithic Proto-Indo-European homeland model of the Russian school of thought: The Steppe hypothesis of Indo-European origins remains to be proven, Acta Archaeologica, 88:1, 193–204.

Abstract:

Recent genetic studies have claimed to reveal a massive migration of the bearers of the Yamnaya culture (Pit-grave culture) to the Central and Northern Europe. This migration has supposedly lead to the formation of the Corded Ware cultures and thereby to the dispersal of Indo-European languages in Europe. The article is a summary presentation of available archaeological, linguistic, genetic and cultural data that demonstrates many discrepancies in the suggested scenario for the transformations caused by the Yamnaya “invasion” some 5000 years ago.

Excerpts:

Both teams [Reich/Anthony, and Willerslev/Kristiansen] interpreted this resemblance in the same way: as evidence of mass migration of the Yamnaya culture from the steppes into the Central and Northern Europe, resulting in the formation of the Corded Ware cultures, and these are universally recognised as Indo-European. Since earlier in this part of Europe existed a different pool of genomes, geneticists presumed that the Yamnaya migration alone had brought the Indo-European languages into Europe. It is difficult to say to what extent the pre-convictions of the involved archaeologists influenced these conclusions, or whether the results of the genetic studies attracted archaeologists with such beliefs.

Mismatch of cultural manifestations

First, we might question the idea of the Yamnaya culture as a unity rather than a loose conglomerate of cultures. Merpert (1974) divided it into nine local groups but did not recognise them as separate cultures. However, in 1975 I suggested that Nerushay (Budzhak) monuments should be recognised as a distinct culture (Klejn 1975), although still as a part of the same broader steppe community.

This was accepted by other specialists (Ivanova 2012; 2013; 2014). Generally, in the western branch of this community, a mixture of the eastern rites of interment with local, Balkan ceramics can be observed. It should be noted that hitherto all genetic samples were taken from eastern material (in the vicinity of Samara in the Volga basin and Kalmykia), while the central thesis concerns the intrusion of the western branch of this community (Budzhak culture) into Europe.

yamnaya-corded-ware.connection
The spread of cultural-historical communities of the Yamnaya culture and the location of the Budzhak culture. GAC – Globular Amphora culture; CWC – Corded Ware culture. After Ivanova 2013.

Simultaneity of cultures

The Yamnaya culture (Chernykh & Orlovskaya 2004a; Heyd 2011; Frȋnculeasa et al. 2015) appears not to be the predecessor of the Corded Ware cultures but is contemporary with them. The Corded Ware cultures appeared also around the turn between the fourth and third millennium BC (Stöckli 2001; Furholt 2003). Their derivation from the Yamnaya seems, therefore, to be less probable. This is evidenced by the fact that the corded beakers or amphorae found in the Budzhak culture are not the prototypes of the corded beakers or amphorae found in more northern territories, but seem instead to be an outcome of contemporaneous contacts (Ivanova 2014; Klejn 2017c).

Discrepancies across the haplogroups

Even more remarkable is the variation in the distribution of types of Y chromosome. In the Yamnaya population, R1b is not just a single occurrence (there are about seven known occurrences) while in the Corded Ware population a different clade of R1b is found and R1a is predominant (several instances). Thus the postulate of unbroken succession finds no support!

yamna-into-corded-ware
Distribution of artefacts and customs of the Yamnaya culture in the area of the Corded Ware cultures. After Bátora 2006.

Paradoxical gradient

In the tables presented in the article by Reichs’ team (Haak et al. 2015) the genetic pool connecting the Yamnaya culture with the Corded Ware people is shown to be more intense in Northern Europe (Norway and Sweden) and decreases gradually from the North to the South (Fig. 6). It is weakest around the Danube, in Hungary, i. e. areas neighbouring the western branch of the Yamnaya culture! This is the reverse image to what the proposed hypothesis by the geneticists would lead us to expect. It is true that this gradient is traced back from the contemporary materials, but it was already present during the Bronze Age (Klejn 2015a).

The author also uses questionable interpretations from selected articles to advance his (as of today) untenable positions regarding a Mesolithic origin of the reconstructible Proto-Indo-European language.

1. Glottochronology, for a PIE origin:

If based on the data of glottochronology (taking into account all disputes) the period of initial dispersal is to be dated to the 7th-5th millennium BC.

2. Doubts on the origin of R1b-L51 subclades expressed in Genetic differentiation between upland and lowland populations shapes the Y-chromosomal landscape of West Asia, by Balanovsky et al. (2017), Human Genetics 136, 4. 437-450:

The currently available dataset does not contradict the hypothesis that R-GG400 marks a link between the East European steppe dwellers and West Asians, though the route and even direction of this migration is disputable. It does, however, demonstrate that present-day West European R1b chromosomes do not originate from the Yamnaya populations analyzed in (Haak et al. 2015; Mathieson et al. 2015) and raises the question of their origin. A Bronze Age origin is more likely than a Neolithic one (Balaresque et al. 2010), but further ancient DNA studies may be necessary to identify this source.

Just yesterday I read the post The retraction paradox: Once you retract, you implicitly have to defend all the many things you haven’t yet retracted, by Andrew Gelman. While – in my opinion – the post does not live up to its title, it poses an interesting question, as to how ad logicam (fallacy fallacy) is often used today in research: One author proposes something that is later demonstrated to be wrong, so everything they wrote or write can be said ipso facto to be wrong…especially if they accept that it was wrong.

This is usual with amateur geneticists (those who don’t publish, and are therefore not subjected to criticism): if anyone is wrong (whether in Archaeology or Genetics), then they are wrong in everything else. It seems to me that Klejn’s theses against recent genetic results rest on the same assumption: The Yamna -> Corded Ware migration model is wrong, ergo the Yamna homeland model is wrong.

I guess this same fallacy is what a lot of angered geneticists (whether professional or amateurs) are going to use to dismiss Klejn’s criticism, trying to focus on what he clearly does not grasp – about genomic data of Yamna peoples and their expansion – to disregard his doubts on genetic interpretations entirely.

I have warned many times about how simplistic interpretations of genetic data would cause a general mistrust in the field, and that archaeologists won’t take the discipline seriously, no matter how many articles get published in famous research tabloids like Nature or Science…

Those who dismiss this warning lightly seem to forget the fate of other recent “scientific breakthroughs” which were initially so promising that Humanities appeared to matter no more, like glottochronology for Linguistics and, to some extent, that of radiocarbon analysis for Archaeology.
EDIT: see here a recent example of discusion on discrepancies between archaeological and 14C-based chronologies, whereby ‘scientific data’ obviously needs archaeological context for a meaningful interpretation

Featured image: The direction of the supposed migration of the bearers of the Yamnaya culture into the area of the Corded Ware cultures. After Haak et al. 2015.

NOTE: I obviously don’t agree with Klejn’s main model: he criticises the Proto-Indo-European steppe homeland, and more specifically the expansion of Yamna peoples with R1b-L23 subclades, which I support. But, probably because of his “pre-convictions” (as he puts it when describing proponents of the steppe hypotheses) about the Proto-Indo-European homeland in Northern Europe during the Mesolithic, he was one of the first renown archaeologists to criticise the obvious inconsistencies in the genetic model of migrations based exclusively on the “Yamnaya ancestral component” concept, and to provoke the necessary reaction from (until then) overconfident geneticists, and he deserves credit for that.

In my opinion, the Russian school’s “Northern European Mesolithic” homeland model – as I have said before – could be based on the appearance of EHG ancestry, or maybe on the expansion of haplogroup R1b with post-Swiderian cultures, but the timeframe proposed is too early for any reconstructible parent proto-language, even for Indo-Uralic.

Related:

Differences in ADMIXTURE between Khvalynsk/Yamna and Sredni Stog/Corded Ware

neolithic-steppe

Looking for differences among steppe cultures in Genomics is like looking for a needle in a haystack.

It means, after all, looking for differences among closely related cultures, such as between South-Western and North-Western Anatolian Neolithic cultures, or among Old European cultures (such as Vinča or Cucuteni–Trypillia), or between Iberian cultures after the arrival of steppe-related populations.

These differences between closely related regions, in all these cases and especially among steppe cultures, even when they are supported by Archaeology and anthropological models of migration (and compatible with linguistic models), are expected to be minimal.

Fortunately, we have phylogeography, which helps us point in the right direction when assessing potential migrations using genomic data.

User Tomenable recently pointed out a curious finding on Anthrogenica, from data available in Mathieson et al (2017): in ADMIXTURE results with K=12, a different ancestral component (in light green in the paper, see below) is traceable from the North Caspian steppe since the Neolithic. This is also partially distinguishable on K=10 and K=11, although not so clearly differentiating among later cultures.

NOTE: Read more on the controversy regarding the ideal number of ancestral populations, the absurd use of ADMIXTURE to solve language questions, and the meaning of cross-validation (CV) values

admixture-khvalynsk-yamna-sredni-stog-cwc
Unsupervised ADMIXTURE plot from k=10 to 12, on a dataset consisting of 1099 present-day individuals and 476 ancient individuals. We show newly reported ancient individuals and some previously published individuals for comparison.

Explanations for this finding might include, as the user points out, a greater contribution of CHG ancestry in the eastern steppe cultures (Khvalynsk/Yamna) compared to the North Pontic steppe (Sredni Stog/Corded Ware), which is probably one of the main genomic differences among both cultures, as I pointed out in the Indo-European demic diffusion model (see accounts on the origins of Khvalynsk and Sredni Stog populations and on contacts between Yamna and the Caucasus, and see below also my sketch of Eurasian genomic history).

Interesting is also the appearance of similar ancestral components later in Vučedol – which probably received admixture from Yamna settlers (see admixture components in West Yamna samples and in the Yamna settler from Bulgaria) – , and later still in the Balkans.

On the other hand, previous ancestral components in outliers from the Balkans seem to be more similar to Sredni Stog samples, giving still more strength to the hypothesis that this common (“steppe”) component expanded westward within the Pontic-Caspian steppe with the spread of Suvorovo-Novodanilovka chiefs.

Problems with this interpretation include:

1) The scarce samples available, the different cultures included, and the CV values of the K populations selected in ADMIXTURE.

2) The lack of data for comparison with Bell Beaker peoples (from Olalde et al. 2017).

3) The sample classified as Latvia_LN/CWC has this component. I have already said before that, given the differences with all other Corded Ware samples, this quite early sample might be an outlier, with Khvalynsk/Yamna population connected directly to the ancestors of this individual, possibly through exogamy (as it is clear from my sketch below). Whether or not this is an outlier among CWC populations in the Baltic, only future samples can tell.

4) Three later individuals from Corded Ware in Germany have the component, in a minimal amount. I would bet – judging by their position in the graphic – that this might be explained through the Esperstedt family. These individuals might have in turn got the contribution directly from the oldest member, who shows what seems (in PCA) like a recent admixture from contemporary steppe cultures (such as the Catacomb culture).

NOTE: See my graphics with interesting members of the Espersted family marked: ADMIXTURE and PCA (outlier).

qgraph-eurasia
Tentative sketch modelling the genetic history of Europe and West Eurasia from ancient populations up to the Neolithic, according to results in recent genetic papers and archaeological models of known migrations.

Again, needle in a haystack… And confirmation bias by me, indeed.

But interesting nonetheless.

EDIT (4 JAN 2017): A reader points out that the interpretation of Unsupervised ADMIXTURE should work backwards (i.e. different contributions into different modern populations), and not based solely on ancestral populations, which seems probably right. So again, confirmation bias (and potentially wrong direction fallacy) by me…

Related:

The new “Indo-European Corded Ware Theory” of David Anthony

allentoft-yamna-corded-ware

I recently wrote about the Indo-European Corded Ware Theory of Kristian Kristiansen and his workgroup, a sort of “Danish school”, whose aim is to prove a direct, long-lasting interaction between the North Pontic steppe and east European cultures during the Late Neolithic, which supposedly gave rise to a Late Indo-European-speaking Corded Ware culture. That is, a sort of renewed Kurgan model; or, more exactly, Kurgan models, since there is no single one preferred right now.

David Anthony had remained more or less in the background after the controversial assessment of the so-called Yamnaya ancestral component by recent genetic papers, which posited that there was a genetic flow in the Late Neolithic suggesting a migration model that could be hypothetically simplified to Yamna -> Corded Ware -> Bell Beaker.

With his previous publications, especially The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World (and its revisions), Anthony had set up an impressive revised steppe theory that overcame some of the errors of Gimbutas’ Kurgan model.

Whereas Indo-European-speaking Corded Ware cultures (CWC) were still featured prominently in his model, the different languages supposedly spoken by these groups were explained through multiple cultural diffusion events, and actual migrations from Yamna peoples were only described into Early Bronze Age cultures of the Balkans, and into the Afanasevo culture.

More recently, he has offered (in collaboration with his wife, Dorcas R. Brown) a tentative original connection Yamna -> Corded Ware in the Lesser Poland region, in their paper Molecular archaeology and Indo-European linguistics: Impressions from new data. It seemed to be based merely on recent genetic finds, and on the fact that Corded Ware remains appear to be oldest in that region, according to radiocarbon analysis.

Now he seems to be more and more supportive of this hypothesis in his new essay, Archaeology and Language: Why Archaeologists Care About the Indo-European Problem, in European Archaeology as Anthropology: Essays in Memory of Bernard Wailes ed by P.J. Crabtree and P. Bogucki (2017).

The chapter is interesting to read, as always. Nevertheless, it commits to previous errors – driven by the wrong interpretation of recent genetic papers -, and deepens thus this untenable archaeological-linguistic model of migrations from the steppe, in a weird vicious circle of wrong feedback between archaeologists and geneticists that diregards what archaeologists have been saying in the last decade.

Instead of waiting for the current storm of genetic papers (and their misinformation) to pass, and see what remains, Anthony is now supporting a different model than the one that made him popular, risking the good name he has earned in Archaeology and in popular science texts – in spite of initial setbacks due to the prevailing criticisms of Indo-European migration models.

Some excerpts (emphasis mine):

indo-european-corded-ware-bell-beaker
Central and Eastern Europe ca. 3000–2500 BCE showing the early Yamnaya culture area 3300–2700 BCE and the Yamnaya migration up the Danube Valley with related/offshoot Makó and Vučedol sites; also the distribution of Corded Ware sites in northern Europe; and site areas sampled for aDNA in Haak et al. (2015). The oldest Corded Ware radiocarbon dates are from southern and central Poland. The Yamnaya cemeteries in the Danube Valley are after Heyd (2011), the shaded Globular Amphorae site area is after Harrison and Heyd (2007); the Corded Ware and Globular Amphorae sites in southern Poland are after Machnik (1999); and the blue dots were all Corded Ware sites with radiocarbon dates as of Furholt (2003).

A Yamnaya migration from the steppes up the Danube valley as far as Hungary was already accepted by many archaeologists (Fig. 2.2). Hundreds of Yamnaya-type kurgans and dozens of cemeteries have been recognized by archaeologists in the lower Danube valley, in Bulgaria and Romania; and in the middle Danube valley, in eastern Hungary, with radiocarbon dates that began about 3000–2800 BCE and extended to about 2700–2600 BCE (Ecsedy 1979; Sherratt 1986; Boyadziev 1995; Harrison and Heyd 2007; Heyd 2012; Frînculeasa et al. 2015). The migration stream that created these intrusive cemeteries now can be seen to have continued from eastern Hungary across the Carpathians into southern Poland, where the earliest material traits of the Corded Ware horizon appeared (Furholt 2003). Corded Ware sites appeared in Denmark by 2800–2700 BCE, probably within 100–200 years after the first Yamnaya migrants entered the lower Danube valley. This surprisingly rapid migration introduced genetic traits such as the R1a and R1b Y-chromosome haplogroups and a substantial element of ANE (Ancient North Eurasian) ancestry that remain characteristic of most northern and western Europeans today.

(…)

The oldest radiocarbon dates from Corded Ware sites occur in southern Poland (upper Vistula) and north-central Poland (Kujavia), and this was seen as the region where the early networking of amphorae styles from Globular Amphorae and axe types from Scandinavia began. The genetic evidence shows a somewhat different picture: the Corded Ware people were largely immigrants whose ancestors came from the steppes (probably immediately from eastern Hungary), but they quickly adopted local material traits in amphorae and axe types that obscured their foreign origins. Middle Neolithic northern European populations composed of admixed WHG/EEF survived but were largely excluded from Corded Ware cemeteries, and from marriage into the Corded Ware population. Even centuries after the initial migration the Corded Ware population at Esperstedt, dated 2500–2400 BCE, still exhibited 70–80% Yamnaya genes, although individual variations in the extent of local admixture were apparent. Intermarriage with the surviving local population was more frequent during the ensuing Bell Beaker period. However, the resurgence is more visible in mtDNA than in Y-DNA (Szécsényi-Nagy et al. 2015), suggesting that men of the older EEF heritage were disadvantaged more than women.

(…)

Settlements were more permanent before the Corded Ware migration, and remained so among the Globular Amphorae people, who continued to create more localized site-and-cemetery groups in the same landscape with the more mobile immigrants. Afterward, during the Bell Beaker period, when local genetic ancestry rebounded and the population became more admixed, settlements again were more permanent. The Corded Ware culture introduced both a large, steppe-derived population and an unusually mobile form of pastoral economy that was a regional economic anomaly, but nevertheless survived in varying forms for centuries before the regional economic pattern was re-established. A steppe language certainly accompanied this demographic and economic shift. As we have seen above, there are good independent reasons (loans with Uralic and South Caucasian) to think that PIE was spoken in the steppes. It is likely that the steppe language introduced between 3000–2500 BCE was a late (post-Anatolian) form of PIE and survived and evolved into the later northern IE languages.

So, to sum up the new developments of Anthony’s preferred model:

  1. Abandonment of the multiple cultural diffusion models from Yamna into Corded Ware, i.e. Pre-Germanic (in the Usatovo culture) and Pre-Balto-Slavic (in the Middle Dnieper culture).
  2. The only potential Yamna connection with Corded Ware in Archaeology must come from Yamna migrants in the Carpathian basin. Therefore, R1a must come from Hungarian settlements.
  3. Corded Ware cultures from Northern Europe, from roughly 2800 BC, must come from Yamna settlers of the Carpathian basin.
  4. Esperstedt is a great example of Yamnaya genes, and of the mobility (and lack of intermarriage) of Corded Ware peoples centuries, after their migration from Yamna settlers in Hungary.

My answers (obvious for anyone reading this blog, or my demic diffusion model):

  1. It is a pitty that cultural diffusion models are abandoned. They were the last hope to keep these IE-CWC/Kurgan hypotheses alive.
  2. The Carpathian Basin is obviously the only potential early connection between Corded Ware and Yamna. But no single R1a has been found in western migrants, and admixture (including ancestral components and PCA) from Early Yamna, West Yamna, Balkan EBA, and early Bell Beaker samples from Hungary make it very unlikely that such a connection existed.
  3. Corded Ware peoples formed and began their migration much earlier than Yamna settlers arrived in the Carpathian Basin. Compare e.g. the Late Neolithic sample from Latvia (dated ca. 2885 BC) with steppe ancestry attributed to Corded Ware, or the early appearance of east European cultures like Fatyanovo-Balanovo or Abashevo. Also, known Yamna migration routes don’t include these proposed population expansions.
  4. I have already written about the Esperstedt outlier, and why its definition as an outlier should have been clearly made to avoid this kind of misinterpretations…
yamna-bell-beaker
Yamna – East Bell Beaker migration ca. 3000-2300 BC, according to Heyd (2007)

With each new genetic paper it is less and less likely that many individuals of Y-DNA haplogroup R1a, and especially R1a-Z645 (if any at all), will appear associated with Yamna, either in the Pontic-Caspian steppe or in western settlements (at least clearly belonging to Yamna, Balkan EBA, or Bell Beaker cultures), which will make the life of this new Indo-European Corded Ware Theory model still shorter than could be a priori expected for any archaeological model.

Also, it seems that the Bell Beaker preprint paper by Olalde et al. (2017) will be published in Nature soon with more samples, so a swift rejection of this theory may be near. On the other hand, the first paper on this model by Anthony and Brown (like the first paper of Kristiansen and his workgroup) appeared just before Olalde et al. (2017) and Mathieson et al. (2017), and yet all samples against their pet theories have not deterred any of them to continue supporting them…

I would say it is a shame that some geneticists are misleading good archaeologists into so many different wrong models, but I guess it is only fair to blame authors for what they write, not whom or what they trusted to write…

I think there is much more to be said about the interaction among Neolithic cultures from the steppe (viz. Sredni Stog and Khvalynsk), than about the Yamna migration, and Anthony was in a better position to judge this. Right now, it seems that other researchers like Rassamakin or Ivanova are taking the lead in the research of Neolithic cultures from the steppe, while Heyd or Prescott are taking the lead in the explanation of Yamna -> Bell Beaker migrations and their connection with the expansion of Late Indo-European languages.

#EDIT (December 18 2017): Just to be clear, Anthony’s new Indo-European Corded Ware Theory model in Archaeology would be compatible with the development and expansion of a North-West Indo-European dialect of Late Indo-European in Linguistics (which is my main source of disagreement with other recent models). In fact, Anthony’s new model could explain the different nature of Balto-Slavic, being adopted by peoples of mainly R1a-Z645 subclades of Lesser Poland – from Yamna migrants of R1b-L23 subclades – , and later influencing Pre-Germanic brought by Bell Beakers to Scandinavia, so in that sense it could offer some light to certain controversial linguistic aspects. See Corded Ware Substrate Theory for more on Germanic and Balto-Slavic similarities based on a common, intermediate substrate.

What I am criticising with this post is that the model seems to rely heavily (in fact, almost solely) on what some geneticists (and especially amateurs, fanboys of specific haplogroups and/or admixture components) are selling about the ‘Yamnaya component’ (and thus the assumption of a common migration of peoples of R1a-Z645 and R1b-L23 subclades), something which is – to say the least – highly controversial today. Instead of departing from Archaeology (his field) to try and make sense of what others are saying, he seems to be abandoning his own migration models and adopting one compatible with genetic studies of 2015-2016 made by laymen in Indo-European studies, who based their conclusions on their own new methods, applied to a few scattered samples. These new IECWT proponents are thus in turn giving still more reasons for these geneticists to support wrong assumptions in future studies, by relying on any of these new potential archaeological scenarios. And so on and on it goes…

Related:

The concept of “Outlier” in Human Ancestry (II): Early Khvalynsk, Sredni Stog, West Yamna, Iron Age Bulgaria, Potapovka, Andronovo…

yamna-corded-ware-bell-beaker

I already wrote about the concept of outlier in Human Ancestry, so I am not going to repeat myself. This is just an update of “outliers” in recent studies, and their potential origins (here I will repeat some of the examples):

Early Khvalynsk: the three samples from the Samara region have quite different positions in PCA, from nearest to EHG (of Y-DNA haplogroup R1a) to nearest to ANE ancestry (of Y-DNA haplogroup Q). This could represent the initial consequences of the second wave of ANE ancestry – as found later in Yamna samples from a neighbouring region -, possibly brought then by Eurasian migrants related to haplogroup Q.
With only 3 samples, this is obviously just a tentative explanation of the finds. The samples can only be reasonably said to show an unstable time for the region in terms of admixture (i.e. probably migration), judging by the data on PCA.

Ukraine Eneolithic samples offer a curious example of how the concept of outlier can change radically: from the third version (May 30th) of the preprint paper of Mathieson et al. (2017), when the Ukraine Eneolithic sample with steppe ancestry (and clustering with central European samples) was the ‘outlier’, to the fourth version (September 19th), when two samples with steppe ancestry clustering close to Corded Ware samples were now the ‘normal’ ones (i.e. those representing Ukraine Eneolithic population), and the outlier was the one clustering closely with Ukraine Mesolithic samples…

pca-admixture-yamna
PCA and Admixture for south-eastern Europe. Image modified from Mathieson et al. (2017) – Third revision (May 30th), used in the 2nd edition of the Indo-European demic diffusion model.

This is one of the funny consequences of the wrong interpretation of the ‘yamnaya component’, that made geneticists believe at first that, out of two samples (!), the ‘outlier’ was the one with ‘yamnaya’ ancestry, because this component would have been brought by an eastern immigrant from early Khvalynsk…

This example offers yet another reason why precise anthropological context is necessary to offer the right interpretation of results. Within the Indo-European demic diffusion model – based mainly on Archaeology and Linguistics – , the sample with steppe ancestry was the most logical find in the region for a potential origin of the Corded Ware culture, and it was interpreted as such, well before the publication of the fourth version of Mathieson et al. (2017).

pca-south-east-europe
PCA of South-East European and other European samples. Image modified from Mathieson et al. (2017) – Fourth revision (September 19th), used in the 3rd edition of the Indo-European demic diffusion model.

West Yamna (to insist on the same question, the ‘yamnaya’ component): we have only four western Yamna samples, two of them showing Anatolian Neolithic ancestry (one of them, from Ukraine, with a strong ‘southern’ drift). On the other hand, Corded Ware migrants do not show this. So we could infer that their migrations were not coetaneous: whereas peoples of Corded Ware culture expanded ca. 3300 BC to the north – in the natural corridor to the Baltic that has been proposed for this culture in Archaeology for decades (and that is well represented by Ukraine Eneolithic samples) -, peoples of Yamna culture expanded to the west, replacing the Ukraine Eneolithic population (i.e. probably those of ‘Proto-Corded Ware culture’), and eventually mixing with Balkan populations of Anatolian Neolithic ancestry.

Potapovka, Andronovo, and Srubna: while Potapovka clusters closely to the steppe, and Andronovo (like Sintashta) clusters closely to Corded Ware (i.e. Ukraine Neolithic / Central-East European), both have certain ‘outliers’ in PCA: the former has one individual clustering closely to Corded Ware, and the latter to the steppe. Both ‘outliers’ fit well with the interpretation of the recent mixture of Corded Ware peoples with steppe populations, and they offer a different image for the evolution of populations of Potapovka and Sintashta-Petrovka, potentially influencing their language. The position of Srubna samples, nearer to Sintashta and Andronovo (but occupying the same territory as the previous Potapovka) offers the image of a late westward conquest from Corded Ware-related populations.

asia-early-bronze
Diachronic map of migrations ca. 2250-1750 BC

Iron Age Bulgaria: a sample of haplogroup R1a-z93, with more ‘yamnaya’ ancestry than any other previous sample from the Balkans. For some, it might mean continuity from an older time. However – as with the Corded Ware outlier from Esperstedt before it – it is more likely a recent migrant from the steppe. The most likely origin of this individual is therefore people from the steppe, i.e. either the Srubna culture or a related group. Its relatively close cluster in PCA to certain recent Slavic populations can be interpreted in light of the multiple back and forth migrations in the region: of steppe populations to the west (Srubna, Cimmerians, Scythians, Sarmatians,…), and of Slavic-speaking populations:

middle-bronze-age-middle-east
Diachronic map of Bronze Age migrations ca. 1750-1250 BC.

Well-defined outliers are, therefore, essential to understand a recent history of admixture. On the other hand, the very concept of “outlier” can be a dangerous tool – when the lack of enough samples makes their classification as as such unjustified -, leading to the wrong interpretations.

Related:

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:

Globular Amphora not linked to Pontic steppe migrants – more data against Kristiansen’s Kurgan model of Indo-European expansion

eneolithic-steppe-cultures

New open access article, Genome diversity in the Neolithic Globular Amphorae culture and the spread of Indo-European languages, by Tassi et al. (2017).

Abstract:

It is unclear whether Indo-European languages in Europe spread from the Pontic steppes in the late Neolithic, or from Anatolia in the Early Neolithic. Under the former hypothesis, people of the Globular Amphorae culture (GAC) would be descended from Eastern ancestors, likely representing the Yamnaya culture. However, nuclear (six individuals typed for 597 573 SNPs) and mitochondrial (11 complete sequences) DNA from the GAC appear closer to those of earlier Neolithic groups than to the DNA of all other populations related to the Pontic steppe migration. Explicit comparisons of alternative demographic models via approximate Bayesian computation confirmed this pattern. These results are not in contrast to Late Neolithic gene flow from the Pontic steppes into Central Europe. However, they add nuance to this model, showing that the eastern affinities of the GAC in the archaeological record reflect cultural influences from other groups from the East, rather than the movement of people.

globular-amphora-pca-admixture
(a) Principal component analysis on genomic diversity in ancient and modern individuals. (b) K = 3,4 ADMIXTURE analysis based only on ancient variation. (a) Principal component analysis of 777 modern West Eurasian samples with 199 ancient samples. Only transversions considered in the PCA (to avoid confounding effects of post-mortem damage). We represented modern individuals as grey dots, and used coloured and labelled symbols to represent the ancient individuals. (b) Admixture plots at K = 3 and K = 4 of the analysis conducted only considering the ancient individuals. The full plot is shown in electronic supplementary material, figure S7. The ancient populations are sorted by a temporal scale from Pleistocene to Iron Age. The GAC samples of this study are displayed in the box on the right.

Excerpt, from the discussion:

In its classical formulation, the Kurgan hypothesis, i.e. a late Neolithic spread of proto-Indo-European languages from the Pontic steppes, regards the GAC people as largely descended from Late Neolithic ancestors from the East, most likely representing the Yamna culture; these populations then continued their Westward movement, giving rise to the later Corded Ware and Bell Beaker cultures. Gimbutas [23] suggested that the spread of Indo-European languages involved conflict, with eastern populations spreading their languages and customs to previously established European groups, which implies some degree of demographic change in the areas affected by the process. The genomic variation observed in GAC individuals from Kierzkowo, Poland, does not seem to agree with this view. Indeed, at the nuclear level, the GAC people show minor genetic affinities with the other populations related with the Kurgan Hypothesis, including the Yamna. On the contrary, they are similar to Early-Middle Neolithic populations, even geographically distant ones, from Iberia or Sweden. As already found for other Late Neolithic populations [18], in the GAC people’s genome there is a component related to those of much earlier hunting-gathering communities, probably a sign of admixture with them. At the nuclear level, there is a recognizable genealogical continuity from Yamna to Corded Ware. However, the view that the GAC people represented an intermediate phase in this large-scale migration finds no support in bi-dimensional representations of genome diversity (PCA and MDS), ADMIXTURE graphs, or in the set of estimated f3-statistics.

globular-amphora-hunter-gatherer-farmer-yamnaya
Scheme summarizing the five alternative models compared via ABC random forest. We generated by coalescent simulation mtDNA sequences under five models, differing as to the number of migration events considered. The coloured lines represent the ancient samples included in the analysis, namely Unetice (yellow line), Bell Beaker (purple line), Corded Ware (green line) and Globular Amphorae (red line) from Central Europe, Yamnaya (light blue line) and Srubnaya (brown line) from Eastern Europe. The arrows refer to the three waves of migration tested. Model NOMIG was the simplest one, in which the six populations did not have any genetic exchanges; models MIG1, MIG2 and MIG1, 2 differed from NOMIG in that they included the migration events number 1, 2 (from Eastern to Central Europe, respectively before and after the onset of the GAC), or both. Model MIG2, 3 represents a modification of MIG2 model also including a back migration from Central to Eastern Europe after the development of the Corded Ware culture.

Together with Globular Amphora culture samples from Mathieson et al. (2017), this suggests that Kristiansen’s Indo-European Corded Ware Theory is wrong, even in its latest revised models of 2017.

gimbutas-kurgan-indo-european
The background shading indicates the tree migratory waves proposed by Marija Gimbutas, and personally
checked by her in 1995. The symbols refer to the ancient populations considered in the ABC analysis

On the other hand, the article’s genetic finds have some interesting connections in terms of mtDNA phylogeography, but without a proper archaeological model it is difficult to explain them.

mtdna-yamnaya-gac-corded-ware-bell-beaker
Haplogroup frequencies were obtained for Early Neolithic (EN), Middle Neolithic (MN), Chalcolithic (CA), and Late Neolithic (LN). The color assigned to each haplogroup is represented on the lower right part of each plot. Haplogroup frequencies were plotted geographically using QGIS v2.14.

Text and images from the article under Creative Commons Attribution 4.0 license.

Discovered first via Bernard Sécher’s blog.

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