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Monday, February 13, 2023

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

Friday, January 13, 2023

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

Almost a decade ago scientists at the David Reich Lab extracted DNA from the remains of three men from the Khvalynsk II cemetery at the northern end of the Pontic-Caspian (PC) steppe.

These Eneolithic Eastern Europeans showed significant genetic heterogeneity, with highly variable levels of Eastern Hunter-Gatherer (EHG) and Near Eastern-related ancestry components.

As a result, the people at the David Reich Lab concluded that the Eneolithic populations of the PC steppe formed from a relatively recent admixture between local hunter-gatherers and Near Eastern migrants.

Unfortunately, this view has since become the consensus among scientists working with ancient DNA.

I say unfortunately because there's a more straightforward and indeed obvious explanation for the genetic heterogeneity among the samples from Khvalynsk II. It's also the only correct explanation, and it doesn't involve any recent gene flow from the Near East.

Here it is, in point form, as simply as I can put it:

- EHG is best represented by samples from Karelia and Lebyazhinka, which are modern-day Russian localities in the forest zone and on the border between the steppe and the forest-steppe, respectively

- Khvalynsk II is also located on the boundary between the steppe and the forest-steppe, and very far from the Near East

- so the genetic structure of the people buried at Khvalynsk II does represent an admixture event

- however, this admixture event simply involved an EHG population from the forest-steppe and a very distantly Near Eastern-related group native to the steppe (that is, two different Eastern European populations).

I've written this blog post because I think David Reich, Nick Patterson, Iosif Lazaridis and colleagues should finally admit that they didn't quite get this right. And it'd be nice if they could put out a paper sometime soon in which they set the record straight.

See also...

Monday, January 2, 2023

Trying to catch up

For starters, I need population labels for many of these G25 coords:

Koptekin et al. 2022

Peltola et al. 2022

Skourtanioti et al. 2023

Varela et al. 2023

Wang et al. 2023

Yu et al. 2023

I'll be running more samples later this week, and I'll need help in organizing them for the G25 datasheets. See comments below for more details.

Sunday, November 13, 2022

A reappraisal of Ashkenazic maternal ancestry

Kevin Brook, who occasionally comments on this blog, has published a peer-reviewed book titled The Maternal Genetic Lineages of Ashkenazic Jews.

The book focuses on 129 mitochondrial (mtDNA) haplogroups that are found in present-day Ashkenazic Jews, and reveals that these lineages can be traced back to a wide range of places, such as Israel, Italy, Poland, Germany, North Africa, and China.

Ergo, it argues that both Israelites and converts to Judaism from a variety of gentile groups made lasting contributions to the Ashkenazic maternal gene pool. In Kevin's own words, the book also:

- shows that all Ashkenazim remain genetically linked to a significant degree to other types of Jewish populations, not only paternally but maternally as well

- disproves the myth that Cossack rapists were responsible for any of the non-Israelite DNA in Ashkenazim

- presents new DNA evidence in favor of a small contribution of Khazarian and Alan converts to Judaism to the Ashkenazic gene pool.

That makes good sense based on what I've learned over the years from studying modern and ancient genome-wide Ashkenazic DNA. More information about Kevin's book is available at the website HERE.

See also...

My take on the Erfurt Jews

Tuesday, November 1, 2022

The story of R-V1636

Who wants to bet against this map? Keep in mind that ART038 (~3000 calBCE) remains the oldest sample with the V1636 and R1b Y-chromosome mutations in the West Asian ancient DNA record. Ergo, there's nothing to suggest that V1636 or R1b entered Eastern Europe from West Asia.

See also...

A tantalizing link

How relevant is Arslantepe to the PIE homeland debate?

Thursday, October 27, 2022

The Yassitepe challenge

This is about the only successful qpAdm model that I can find for the pair of Early Bronze Age (EBA) females from Yassitepe, Turkey, using a decent set of outgroups and markers. I wouldn't take it too literally, but it does suggest a potentially significant level of European ancestry, including some steppe ancestry, in these Yassitepe individuals.

AZE_Caucasus_lowlands_LN 0.565±0.054
ROU_N 0.387±0.041
RUS_Progress_En 0.048±0.022

P-value 0.103248
Full output

If anyone reading this can find a better, more convincing solution then I'd love to see it. Feel free to share it in the comments below.

Obviously, both of the Yassitepe samples are from the recent Lazaridis, Alpaslan-Roodenberg et al. paper. Their EBA dating suggests that they might be relevant to the debate over the origins of Anatolian speakers, such as the Hittites and Luwians.

See also...

Dear Iosif, about that ~2%

The precursor of the Trojans

Thursday, October 13, 2022

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_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

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

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_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.

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?

Thursday, October 6, 2022

Balto-Slavs and Sarmatians in the Battle of Himera

G25 coordinates for most of the samples from the recent Reitsema et al. paper are available in a text file here. They're also in the G25 datasheets at the usual link here.

A basic distance analysis with the G25 data at Vahaduo shows that the two samples labeled Himera_480BCE_3 are either early Balts or Slavs. I suspect that they're Slavs, because I believe that early Slavs had this type of Baltic-like genetic structure before mixing with their non-Slavic-speaking neighbors. Well, that's my pet theory for now, so take it or leave it.

Distance to: ITA_Sicily_Himera_480BCE_3:I10943
0.03393838 HUN_IA_La_Tene_o:I18226
0.03572886 DEU_MA_Krakauer_Berg:KRA001
0.03618075 RUS_Pskov_VA:VK159
0.03899963 SWE_Gotland_VA:VK463
0.03915018 Baltic_EST_IA:s19_V12_1

Distance to: ITA_Sicily_Himera_480BCE_3:I10949
0.03573636 HUN_IA_La_Tene_o3:I25524
0.03698768 HUN_IA_La_Tene_o:I18226
0.03732752 SWE_Skara_VA:VK397
0.03767022 Baltic_EST_IA:s19_V12_1
0.03772687 DEU_MA_Krakauer_Berg:KRA001

On the other hand, I'm almost certain that the two Himera_480BCE_4 samples are Sarmatians. The good old G25 does it again!

Distance to: ITA_Sicily_Himera_480BCE_4:I10944
0.03100861 KAZ_Segizsay_Sarmatian:SGZ002
0.03548059 MDA_Sarmatian:I11925
0.03619219 RUS_Urals_Sarmatian:MJ56
0.03626538 RUS_Urals_Sarmatian:chy001
0.03904260 RUS_Urals_Sarmatian:MJ41

Distance to: ITA_Sicily_Himera_480BCE_4:I10947
0.02989458 RUS_Urals_Sarmatian:MJ43
0.03052790 RUS_Urals_Sarmatian:chy002
0.03170622 KAZ_Kangju:DA226
0.03288789 TUR_BlackSea_Samsun_Anc_C:I4529
0.03310149 KAZ_Aigyrly_Sarmatian:AIG003
See also...

Slavic-like Medieval Germans

Monday, September 19, 2022

Dear Iosif...Yamnaya

Even though the Yamnaya culture probably originated in what is now Ukraine, the earliest Yamnaya samples currently available are from the modern-day Samara region of Russia. They mostly date to around 3,000 BCE. I can analyze their ancestry using Principal Component Analysis (PCA) data.

Target: RUS_Yamnaya_Samara
Distance: 3.2816% / 0.03281581
81.0 RUS_Progress_En
14.4 UKR_N
4.6 HUN_Vinca_MN
0.0 ARM_Aknashen_N
0.0 ARM_Masis_Blur_N
0.0 AZE_Caucasus_lowlands_LN
0.0 BGR_C
0.0 BGR_Dzhulyunitsa_N
0.0 IRN_Ganj_Dareh_N
0.0 IRN_Hajji_Firuz_C
0.0 IRN_Seh_Gabi_C
0.0 IRN_Tepe_Abdul_Hosein_N
0.0 IRN_Wezmeh_N
0.0 RUS_Darkveti-Meshoko_En
0.0 RUS_Maykop
0.0 RUS_Maykop_Late
0.0 RUS_Maykop_Novosvobodnaya

The above results show exactly zero ancestry from West Asia. Admittedly, both RUS_Progress_En and HUN_Vinca_MN are European ancients with significant West Asian-related ancestry. However, this ancestry is very distantly West Asian-related, and, for instance, it almost certainly has no relevance to the Indo-Anatolian homeland debate.

The Afanasievo culture of Central Asia is regarded to have been an early offshoot of the Yamnaya culture. A good number of Afanasievo samples are available, so let's have a look if their results match those of the Yamnaya folks. And indeed they do, since BGR_C is very similar to HUN_Vinca_MN.

Target: RUS_Afanasievo
Distance: 3.4055% / 0.03405499
84.0 RUS_Progress_En
11.4 UKR_N
4.6 BGR_C
0.0 ARM_Aknashen_N
0.0 ARM_Masis_Blur_N
0.0 AZE_Caucasus_lowlands_LN
0.0 BGR_Dzhulyunitsa_N
0.0 HUN_Vinca_MN
0.0 IRN_Ganj_Dareh_N
0.0 IRN_Hajji_Firuz_C
0.0 IRN_Seh_Gabi_C
0.0 IRN_Tepe_Abdul_Hosein_N
0.0 IRN_Wezmeh_N
0.0 RUS_Darkveti-Meshoko_En
0.0 RUS_Maykop
0.0 RUS_Maykop_Late
0.0 RUS_Maykop_Novosvobodnaya

To try this at home, stick the PCA data in the text file here into the relevant fields here and cranck up the "Cycles" to 4X. You should see exactly zero ancestry from West Asia every time.

I can, more or less, reproduce these results with tools that are routinely used in peer reviewed papers. Below is a table of mixture models produced with the qpAdm software. I set the pass threshold to P ≥0.05, which is an arbitrary value, but the pattern is clear. The full output from each qpAdm run is available here.

Importantly, qpAdm needs to be fed the relevant "right pop" outgroups to be able to discriminate accurately between reference populations.

right pops:

So, for instance, if one were to use in this role the modern-day Mbuti people, as opposed to, say, the ancient hunter-gatherers of Shum Laka, one might find that many models look statistically better than they should. And then one might also find that the Yamnaya samples carry significant West Asian ancestry.

Actually, I'm not opposed to the idea of some West Asian ancestry in Yamnaya. Indeed, considering the extraordinary mobility of the Yamnaya people and their Eneolithic predecessors on the Pontic-Caspian steppe, it would be unusual if they didn't come into close contact and mix, to some degree, with their neighbors from West Asia.

However, based on everything I've seen, from uniparental markers to different types of autosomal genetic tests, it's clear to me that there's no substantial West Asian ancestry in any Yamnaya samples, except for an outlier female from modern-day Ozera, Ukraine (see here).

Admittedly, ancient DNA does have a habit of throwing curveballs, so I'm eagerly awaiting new Eneolithic samples from the Pontic-Caspian steppe, particularly those associated with the Yamnaya-like Sredni Stog culture, to help finally settle this issue.

Believe it or not, a contact recently sent me a supposedly unpublished female sample from a ~4,200 BCE Sredni Stog burial in modern-day Igren, east central Ukraine. So what the hell, let's assume for the time being that this sample is genuine. This is how Miss Sredni Stog behaves in my PCA mixture test.

Target: UKR_Sredni_Stog
Distance: 4.0769% / 0.04076877
75.6 RUS_Progress_En
17.8 UKR_N
6.6 HUN_Vinca_MN
0.0 ARM_Aknashen_N
0.0 ARM_Masis_Blur_N
0.0 AZE_Caucasus_lowlands_LN
0.0 BGR_C
0.0 BGR_Dzhulyunitsa_N
0.0 HUN_Vinca_MN
0.0 IRN_Ganj_Dareh_N
0.0 IRN_Hajji_Firuz_C
0.0 IRN_Seh_Gabi_C
0.0 IRN_Tepe_Abdul_Hosein_N
0.0 IRN_Wezmeh_N
0.0 RUS_Darkveti-Meshoko_En
0.0 RUS_Maykop
0.0 RUS_Maykop_Late
0.0 RUS_Maykop_Novosvobodnaya

Wow, just wow. Have we actually found Miss Proto-Yamnaya? What does qpAdm have to say in the matter?

HUN_Vinca_MN 0.034±0.028
RUS_Progress_En 0.796±0.045
UKR_N 0.170±0.034
P-value 0.41088

Again, this is an excellent match with the results from my PCA test, especially if we take into account the standard errors. However, with qpAdm it's also possible to model this individual's ancestry as part West Asian.

AZE_Caucasus_lowlands_LN 0.056±0.039
RUS_Progress_En 0.761±0.061
UKR_N 0.183±0.036
P-value 0.465667

As I pointed out above, it's plausible for such people to harbor some West Asian ancestry, but I'm very sceptical that this is really the case here, despite the rather solid qpAdm statistical fit. That's because UKR_Sredni_Stog is not a high quality sample, and, from my experience, qpAdm often has problems analyzing fine scale ancestry in singletons or even small groups that show excess DNA damage and/or offer much less than a million markers.

See also...

Dear Iosif, about that ~2%

But Iosif, what about the Phrygians?

Friday, September 9, 2022

Dear Iosif, about that ~2%

The debate over the location of the so called Indo-Anatolian homeland won't be decided by the persistence of any type of genetic ancestry in ancient Anatolia.

It'll be decided by a multidisciplinary study on the interactions between the ancient peoples of the North Pontic steppe, the eastern Balkans, and western Anatolia.

If such a study finds a pulse of steppe-related gene flow from the Balkans into Anatolia sometime during the early metal ages, it'll corroborate the linguistic hypothesis that a language ancestral to Hittite, Luwian and related tongues moved into Anatolia from Eastern Europe.

Why do we only need a pulse of gene flow, you might ask? Obviously, because:

- language and genetic ancestry can start with a strong association but, since they're not linked, they can eventually follow very different trajectories

- the dilution of genetic ancestry is an important factor, especially in ancient West Asia, and it must be taken into account in models of language spread, rather than ignored in favor of simple, elegant models that do not reflect reality.

Here's my favorite quote from the recent Lazaridis, Alpaslan-Roodenberg et al. paper, because, probably unbeknownst to the authors, it's exceptionally revealing about the spread of a wide range of Indo-European speakers into Anatolia.

However, in individuals from Gordion, a Central Anatolian city that was under the control of Hittites before becoming the Phrygian capital and then coming under the control of Persian and Hellenistic rulers, the proportion of Eastern hunter-gatherer ancestry is only ~2%, a tiny fraction for a region controlled by at least four different Indo-European–speaking groups.

Indeed, this is exactly what the Lazaridis, Alpaslan-Roodenberg et al. paper should've been about. That is, the authors should've given us a painstaking account of the spread of different ancient Indo-European speaking groups into Anatolia and explained how, overall, their DNA was rapidly diluted to a trace amount.

However, instead they treated us to a make-believe tale about a so called Indo-Anatolian homeland in what is now Armenia.

See also...

Dear Iosif...Yamnaya

But Iosif, what about the Phrygians?

Dear Iosif...

Dear Iosif #2

Dear Iosif #3