Dear David, Nick, Iosif...let me tell you about Yamnaya

Lazaridis, Alpaslan-Roodenberg et al. recently claimed that the Yamnaya people of the Pontic-Caspian (PC) steppe carried "substantial" ancestry from what is now Armenia or surrounds.

However, this claim is essentially false.

Only one individual associated with the Yamnaya culture shows an unambiguous signal of such ancestry. This is a female usually labeled Ukraine_Yamnaya_Ozera_o:I1917. The "o" suffix indicates that she is an outlier from the main Yamnaya genetic cluster.

Unlike I1917, typical Yamnaya individuals carry a few per cent of ancient European farmer admixture. This ancestry is only very distantly Armenian-related via Neolithic Anatolia (see here).

It's difficult for me to understand how Lazaridis, Alpaslan-Roodenberg et al. missed this. I suspect that they relied too heavily on formal statistics and overinterpreted their results.

Formal statistics are a very useful tool in ancient DNA work. Unfortunately, they're also a relatively blunt tool that often has problems distinguishing between similar sources of gene flow.

There are arguably better methods for studying fine scale ancestry, such as Principal Component Analysis (PCA).

Below is a somewhat special PCA featuring a wide range of ancient populations that plausibly might be relevant to the genetic origins of the Yamnaya people. Unlike most PCA with ancient samples, this PCA doesn't rely on any sort of projection, so that all of the actors are interacting with each other and directly affecting the outcome.

Here's another version of the same plot with a less complicated labeling system. Note that I designed this PCA specifically to differentiate between European populations and those from the Armenian highlands, the Iranian plateau and surrounds.

And here's a close up of the part of the plot that shows the Yamnaya cluster. This cluster is made up of samples associated with the Afanasievo, Catacomb, Poltavka and Yamnaya cultures. All of the individuals in this part of the plot are closely related, which is why they're so tightly packed together. The differentiation between them is caused by admixture from different groups mostly from outside of the PC steppe.

The Yamnaya cluster can be broadly characterized as a population that formed along the genetic continuum between the Eneolithic groups of the Progress region and Neolithic foragers from the Dnieper River valley (Progress_Eneolithic and Ukraine_N, respectively). However, this cluster also shows a slight western shift that is increasingly more pronounced in the Corded Ware samples. This shift is due to the aforementioned admixture from early European farmers.

Indeed, the plot reveals two parallel clines extending west from the Progress samples. One of the clines is made up of the Yamnaya cluster and the Corded Ware samples, and pulls towards the ancient European farmers. The other cline includes Ukraine_Yamnaya_Ozera_o:I1917 and pulls towards samples from the Armenian highlands and surrounds.

Being aware of these two clines and knowing how they came about is important to understanding the genetic prehistory of the PC steppe and indeed of much of Eurasia.

At some point, probably during the late Eneolithic, a Progress-related group experienced gene flow from the west and became the Yamnaya and Corded Ware populations. Sporadically, admixture from the Armenian highlands and the Iranian plateau also entered the PC steppe, giving rise to people like the Steppe Maykop outliers and Ukraine_Yamnaya_Ozera_o:I1917.

Unfortunately, this sort of PCA doesn't offer output suitable for mixture modeling, basically because the recent genetic drift shared by many of the samples creates significant noise.

However, to check that my inferences based on the plot are correct I can create composites with specific ancestry proportions to see how they behave. In the plot below Mix1 is 80% Progress_Eneolithic and 20% Iran_Hajji_Firuz_N, Mix2 is 80% Progress_Eneolithic and 20% Armenia_EBA_Kura_Araxes, while Mix3 is 80% Progress_Eneolithic, 15% Ukraine_N and 5% Hungary_MN_Vinca (Middle Neolithic farmers from the Carpathian Basin).

Obviously, we can't get Yamnaya by mixing Progress_Eneolithic with any ancients from the Armenian highlands or the Iranian plateau. On the other hand, Mix3 works quite well, at least in the first two dimensions. In some of the other dimensions genetic drift specific to Ukraine_N pulls it away from the Yamnaya cluster, but this is to be expected.

By the way, the plots were created with the excellent Vahaduo Custom PCA tool freely available here. It's well worth trying the interactive 3D option using my PCA data. The relevant datasheet is available here.

See also...

Dear David, Nick, Iosif...let's set the record straight

The Caucasus is a semipermeable barrier to gene flow

The Kura-Araxes people deserve better

When discussing the Kura-Araxes culture and its people it's important to understand these key points:

- there is Eastern European steppe ancestry in Kura-Araxes samples, and if you're not seeing it then you're not looking hard enough

- Armenian Kura-Araxes samples are mainly a mixture between three different groups currently best represented in the ancient DNA record by ARM_Areni_C, IRN_Hajji_Firuz_C and RUS_Darkveti-Meshoko_En

- ergo, most of the steppe ancestry in the Kura-Araxes population of what is now Armenia must have been mediated via local Chalcolithic groups like ARM_Areni_C

- Kura-Araxes samples show Mesopotamian-related ancestry, and this mustn't be ignored.

Oh, you don't believe it because you just read a big paper in Science claiming otherwise?

Well, the authors of that paper, Lazaridis, Alpaslan-Roodenberg et al., used distal mixture models to study the ancestry of their Kura-Araxes samples, and such models can miss important details.

Consider these three proximate mixture models for a relatively high quality and very homogenous Kura-Araxes sample set from the aforementioned paper. They were done with the qpAdm software

ARM_Kura-Araxes_Berkaber
ARM_Areni_C 0.239±0.068
IRN_Hajji_Firuz_C 0.379±0.068
RUS_Darkveti-Meshoko_En 0.382±0.054
P-value 0.285122 (Pass)
Full output

ARM_Kura-Araxes_Berkaber
IRN_Hajji_Firuz_C 0.569±0.051
RUS_Darkveti-Meshoko_En 0.363±0.058
RUS_Progress_En 0.068±0.020
P-value 0.20306 (Pass)
Full output

ARM_Kura-Araxes_Berkaber
IRN_Hajji_Firuz_C 0.531±0.060
RUS_Darkveti-Meshoko_En 0.469±0.060
P-value 0.0132579 (Fail)
Full output

Some caveats apply. For instance, the pass threshold (P-value ≥0.05) is arbitrary. But the point is that the models look much better with steppe-related and steppe reference populations (ARM_Areni_C and RUS_Progress_En, respectively).

Moreover, the unique and vital Darkveti-Meshoko population is represented by just one individual. I also have the genotypes of his brother and sister, but relatives aren't allowed in these sorts of tests.

Including a singleton in the analysis means that I can't use the inbreed: YES option, which apparently can be a bad thing. Nevertheless, these models do look very solid.

Indeed, I can also model ARM_Kura-Araxes_Berkaber as practically 100% RUS_Maykop_Novosvobodnaya, perhaps with some excess ARM_Areni_C-related input.

ARM_Kura-Araxes_Berkaber
ARM_Areni_C 0.094±0.087
RUS_Maykop_Novosvobodnaya 0.906±0.087
P-value 0.284259 (Pass)
Full ouput

This makes good sense, because RUS_Maykop_Novosvobodnaya can also be modeled solidly as a mixture between IRN_Hajji_Firuz_C, RUS_Darkveti-Meshoko_En and RUS_Progress_En.

RUS_Maykop_Novosvobodnaya
IRN_Hajji_Firuz_C 0.614±0.056
RUS_Darkveti-Meshoko_En 0.307±0.064
RUS_Progress_En 0.080±0.022
P-value 0.141468 (Pass)
Full output

I don't know whether the genetic relationship between ARM_Kura-Araxes_Berkaber and RUS_Maykop_Novosvobodnaya shown in my model is due to Maykop ancestry in the former. It might just be a coincidence in the sense that the same or similar processes led to the formation of both groups. Feel free to let me know your thoughts about that in the comments.

The fact that the Kura-Araxes people harbored steppe ancestry might be very important in the debate over the location of the so called Indo-Anatolian homeland. For instance, it's possible that the proto-Anatolian language spread from the North Caucasus into Anatolia via the Kura-Araxes culture.

But, admittedly, such a solution doesn't have strong support from historical linguistics data, which suggest that the Indo-Anatolian homeland was located in what is now Ukraine and that Anatolian speakers entered West Asia via the Balkans:

Indo-European cereal terminology suggests a Northwest Pontic homeland for the core Indo-European languages

See also...

R-V1636: Eneolithic steppe > Kura-Araxes?

Dear Iosif...Yamnaya

But Iosif, what about the Phrygians?

Dear Iosif #2

In my last blog post I made a mistake in my interpretation of this quote from Lazaridis, Alpaslan-Roodenberg et al., because it confused the crap out of me:

However, the complete lack of association of R-haplogroup descendants and EHG ancestry in either Armenia or Iran is consistent with either a massive dilution of EHG ancestry in these populations resulting in the dissociation of Y-chromosome lineages from autosomal ancestry over time, or with a scenario in which R-M269 was not associated with substantial EHG ancestry to begin with.

I thought they meant that they couldn't find any Eastern European hunter-gatherer (EHG) ancestry in samples from Armenia or Iran bearing Y-chromosome R1b-M269.

Of course, they did find EHG ancestry in these individuals, it's just that they couldn't establish an association specifically between this type of ancestry and Y-haplogroup R1b.

That is, males with Y-haplogroup R1b in Armenia, Iran and everywhere else generally show about the same level of EHG ancestry as their ethnic kin with other Y-haplogroups.

But so what? Why mention this when discussing the origins of R1b-M269, when it has absolutely no value in this context?

Y-haplogroups aren't linked directly to autosomal DNA, and Lazaridis, Alpaslan-Roodenberg et al. are obviously aware of this (hence their point about the potential massive dilution of EHG ancestry).

In regards to the origins of R1b-M269, and the provenance of West Asian R1b-M269, the really powerful observation is that R1b-M269 shows up rather late and suddenly in the West Asian ancient DNA record along with EHG and steppe ancestry.

That, and the fact that Eastern Europe is an ancient R1b hotbed (while West Asia a desert), means there's virtually no chance that R1b-M269 is native to West Asia. In other words, there was no R1b-M269 in West Asia until the steppe people brought it there from north of the Caucasus.

See also...

Dear Iosif...

Dear Iosif #3

But Iosif, what about the Phrygians?

Dear Iosif, about that ~2%

Dear Iosif...Yamnaya

Domestic horses were introduced into Anatolia and Transcaucasia during the Bronze Age (Guimaraes et al. 2020)

Over at Science Advances at this LINK. This is a very important paper because it basically eliminates West Asia as the source of the modern domestic horse lineage, which leaves the Pontic-Caspian steppe in Eastern Europe as the only viable option.

It also corroborates the linguistic theory that the Proto-Indo-European homeland was located on the Pontic-Caspian steppe. That's because the horse is a key animal in the Proto-Indo-European pantheon, and it appears in Indo-European mythology in intricate roles. This suggests that the speakers of Proto-Indo-European weren't just familiar with the horse but also managed to domesticate it. From the paper:

Abstract: Despite the important roles that horses have played in human history, particularly in the spread of languages and cultures, and correspondingly intensive research on this topic, the origin of domestic horses remains elusive. Several domestication centers have been hypothesized, but most of these have been invalidated through recent paleogenetic studies. Anatolia is a region with an extended history of horse exploitation that has been considered a candidate for the origins of domestic horses but has never been subject to detailed investigation. Our paleogenetic study of pre- and protohistoric horses in Anatolia and the Caucasus, based on a diachronic sample from the early Neolithic to the Iron Age (~8000 to ~1000 BCE) that encompasses the presumed transition from wild to domestic horses (4000 to 3000 BCE), shows the rapid and large-scale introduction of domestic horses at the end of the third millennium BCE. Thus, our results argue strongly against autochthonous independent domestication of horses in Anatolia.

Guimaraes et al., Ancient DNA shows domestic horses were introduced in the southern Caucasus and Anatolia during the Bronze Age, Science Advances 16 Sep 2020: Vol. 6, no. 38, eabb0030, DOI: 10.1126/sciadv.abb0030

See also...

Armenian Highland population prehistory

A new preprint at bioRxiv claims that some sort of large-scale population movement resulted in the spread of Sardinian-like ancestry into both the Armenian Highland and East Africa during or just after the Middle-Late Bronze Age. See Hovhannisyan et al. here.

In all seriousness, my suggestion is that the authors should familiarize themselves with the scientific concept of the sanity check and then try again.

For what it's worth, here's a brief outline of the population history of the Armenian Highland based on what I've learned about the topic from ancient DNA in recent years:

- overall, the Neolithic populations of the Armenian Highland were surely very similar to the Caucasus_lowlands_LN samples from what is now Azerbaijan from the recent Skourtanioti et al. paper (see here)

- Chalcolithic era migrations from the Pontic-Caspian steppe and/or the North Caucasus introduced steppe ancestry to the Armenian Highland, bringing at least some of its populations closer genetically to those of Eastern Europe (a somewhat outdated but still useful blog post about this subject is found here)

- population expansions during the Early Bronze Age associated with the Kura-Araxes cultural phenomenon, which may have originated in what is now Armenia, resulted in a resurgence of indigenous Caucasus hunter-gatherer (CHG) ancestry across the Caucasus, as well as its spread to many other parts of West Asia (see here)

- another significant pulse of Eastern European admixture affected the Armenian Highland during the Middle-Late Bronze Age and Early Iron Age (see here)

- it's not yet completely clear what happened in the Armenian Highland during the Iron Age in terms of significant genetic shifts, due to the lack of ancient human samples from the region dating to this period, but it's still possible that the speakers of proto-Armenian arrived there from the Balkans at this time

- the present-day Armenian gene pool is the result of the processes described above, as well as later events, such as those associated with the Urartian and Ottoman Empires.

Indeed, it's probably not a coincidence that present-day Armenians cluster more or less between the prehistoric populations from the Armenian Highland and surrounds in the Principal Component Analysis (PCA) below.

To see a more detailed and interactive version of the plot, copy paste the data from the text file here into the relevant field at the Vahaduo Globabl25 PCA Views here.

Citation...

Hovhannisyan et al., AN ADMIXTURE SIGNAL IN ARMENIANS AROUND THE END OF THE BRONZE AGE REVEALS WIDESPREAD POPULATION MOVEMENT ACROSS THE MIDDLE EAST, bioRxiv, Posted June 24, 2020, doi: https://doi.org/10.1101/2020.06.24.168781

See also...

Armenian confirmation bias

Perhaps a hint of things to come

Understanding the Eneolithic steppe

Early chariot riders of Transcaucasia came from...

I'm finding it increasingly difficult nowadays to fully appreciate all of the ancient DNA samples that are accumulating in my dataset. But it's not entirely my fault.

Among the hundreds of ancient samples published last year there was a couple of Middle Bronze Age (MBA) individuals from what is now Armenia labeled "Lchashen Metsamor" (see here). I wasn't planning to do much with these samples because, even after reading the Nature paper that they came with a couple times over, I didn't have a clue what they were about. But after some digging around, I now know that their people, those associated with the Lchashen Metsamor archeological culture, were among the earliest in Transcaucasia, and indeed the Near East, to use the revolutionary spoked-wheel horse chariot. How awesome is that?

The invention of the spoked-wheel chariot is generally credited to the Middle Bronze Age Sintashta culture of the Trans-Ural steppe in Central Asia, and its rapid spread is often associated with the early expansions of Indo-European languages deep into Asia. On the other hand, some have argued that this type of chariot was first developed in the Near East, and directly derived from solid-wheeled wagons pulled by donkeys.

It's now obvious, thanks to ancient DNA, that the Sintashta people were by and large migrants to Central Asia from somewhere in Eastern Europe, and that they didn't harbor any recent ancestry from the Near East. So if chariot technology spread into the steppes from the Near East, then it did so without any accompanying gene flow, which is possible but not entirely convincing. This begs the question of whether the Lchashen Metsamor population was of Sintashta-related origin, because if it was, then this would corroborate the consensus that spoked-wheel chariots were introduced into Transcaucasia from the steppes to the north.

Below is a Principal Component Analysis (PCA) of West Eurasian genetic variation. It does suggest that the Lchashen Metsamor pair (labeled Armenia_MBA_Lchashen), as well as most of the other currently available samples from what is now Armenia dating to the Middle to Late Bronze Age (MLBA), harbor some steppe ancestry. That's because they appear to form a cline between samples associated with the Sintashta and Kura-Araxes cultures. Of course, the Kura-Araxes culture was a major Early Bronze Age (EBA) archeological phenomenon centered on Transcaucasia and surrounds, so its population can be reasonably assumed to have formed the genetic base of most subsequent populations in the region. The relevant PCA datasheet is available here.

To investigate the possibility of Sintashta-related admixture in Lchashen Metsamor with formal methods, I ran a series of mixture models with the qpAdm software. Here are the three statistically most sound outcomes that I was able to come up with for Lchashen Metsamor:

Armenia_MBA_Lchashen
CWC_Kuyavia 0.183±0.036
Kura-Araxes_Kaps 0.817±0.036
chisq 13.941
tail prob 0.378021
Full output

Armenia_MBA_Lchashen
Balkans_BA_I2163 0.193±0.045
Kura-Araxes_Kaps 0.807±0.045
chisq 14.780
tail prob 0.321267
Full output

Armenia_MBA_Lchashen
Kura-Araxes_Kaps 0.788±0.043
Sintashta_MLBA 0.212±0.043
chisq 14.871
tail prob 0.315451
Full output

I sorted the output by "tail prob", but the fact that Sintashta_MLBA is in third place isn't a problem because the stats in all of these models are basically identical. Indeed, CWC_Kuyavia (Corded Ware culture samples from present-day Kuyavia, North-Central Poland) and Balkans_BA_I2163 (a Bronze Age singleton from what is now Bulgaria) are both very similar and probably closely related to each other and to the Sintashta samples.

Interestingly, and, I'd say, importantly, ancients from the steppe that are closest to Lchashen Metsamor in both space and time, but not particularly closely related to the Sintashta people, don't work too well as a mixture source in such models.

Armenia_MBA_Lchashen
Kubano-Tersk 0.184±0.046
Kura-Araxes_Kaps 0.816±0.046
chisq 22.179
tail prob 0.0526526
Full output

A couple of months ago I suggested that populations associated with the Early to Middle Bronze Age (EMBA) Catacomb culture were the vector for the spread of steppe ancestry into what is now Armenia during the MLBA (see here). After taking a closer look at the Lchashen Metsamor samples, I now think that the peoples of the Sintashta and related cultures were also important in this process. If so, they may have moved from the steppe into Transcaucasia both from the west via the Balkans and the east via Central Asia, and brought with them spoked-wheel chariots. I don't have a clue what language they spoke, but I'm guessing that it may have been something Indo-European.

See also...

The mystery of the Sintashta people

A potentially violent end to the Kura-Araxes Culture (Alizadeh et al. 2018)

Late PIE ground zero now obvious; location of PIE homeland still uncertain, but...

Catacomb > Armenia_MLBA

It's now clear, thanks to ancient DNA, that Transcaucasia and surrounds were affected by multiple, and at times significant, population movements from Eastern Europe during the Chalcolithic and Bronze Age periods. Based on the ancient samples from what is now Armenia, I'd say that this process peaked during the Middle Bronze Age. But who exactly were the people who perhaps swarmed south of the Caucasus at this time?

The most likely suspects are the various groups that occupied the southernmost parts of the Pontic-Caspian steppe throughout the Bronze Age. They were associated with the so called Catacomb, Kubano-Tersk and Yamnaya archeological cultures. Below is a Principal Component Analysis (PCA) that compares samples from these cultures with those from Middle to Late Bronze Age Armenia (labeled Armenia_MLBA). The relevant datasheet is available here.

Note that Armenia_MLBA forms a cline that appears to be stretching out towards the Catacomb, Kubano-Tersk, Yamnaya and other Bronze Age steppe groups, and this suggests that it harbors significant and probably recent steppe-related ancestry. But PCA plots based on just two dimensions of genetic variation can be misleading at times, so let's check this out with some formal mixture models using qpAdm.

Armenia_MLBA
Catacomb 0.234±0.028
Kura-Araxes_Kaps 0.766±0.028
chisq 10.723
tail prob 0.826248
Full output

Armenia_MLBA
Kubano-Tersk 0.254±0.030
Kura-Araxes_Kaps 0.746±0.030
chisq 13.535
tail prob 0.633284
Full output

Armenia_MLBA
Kura-Araxes_Kaps 0.768±0.028
Yamnaya_Kalmykia 0.232±0.028
chisq 14.454
tail prob 0.564954
Full output

Armenia_MLBA
Kura-Araxes_Kaps 0.762±0.029
Yamnaya_Caucasus 0.238±0.029
chisq 15.916
tail prob 0.458816
Full output

All of these models are statistically very sound, and even though I ranked the results by "tail prob", there's nothing in the output that clearly points to any one of the southern steppe groups as the obvious source of the steppe-related ancestry in Armenia_MLBA. But, interestingly, Catacomb tops the ranking, and it probably also makes the most sense based simply on Carbon-14 chronology. So, for now, I'm going with Catacomb.

I didn't get a chance yet to investigate this issue in detail with the Global25. Does it contradict the results from my PCA and qpAdm analyses? If anyone reading this would like to take a close look that'd be great. Feel free to post your findings in the comments below. And if the answer is indeed Catacomb, then what language did these Catacomb-derived migrants, or perhaps invaders, speak? If not proto-Armenian then what?

By the way, please be aware that the Kubano-Tersk samples in my analyses are the same individuals as those featured in Wang et al. 2019 under the label "North Caucasus".

See also...

Early chariot drivers of Transcaucasia came from...

Likely Yamnaya incursion(s) into Northwestern Iran

Late PIE ground zero now obvious; location of PIE homeland still uncertain, but...