How did steppe ancestry spread into the Biblical-era Levant?

It's likely that at least two of the Philistines from Feldman et al. 2019 harbor relatively recent steppe ancestry. They're labeled ASH067 and ASH068 in the paper. The former individual is a male who belongs to Y-chromosome haplogroup R1, which appears to be R1b-M269 judging by the data from the relevant BAM file.

This is just the second instance of Y-haplogroup R1 from the pre-Crusades Levant, and, of course, neither R1 nor R1b-M269 appear in the Near Eastern ancient DNA record prior to the expansions of the Yamnaya and other closely related pastoralist groups from the steppes and forest steppes of Eastern Europe.

So how did the Yamnaya-related ancestry spread into the Biblical-era Levant? Did it come via Anatolia, the Caucasus and/or the Mediterranean?

To try and answer this question I analyzed separately the genome-wide data for ASH067 and ASH068 with qpAdm, relying on outgroup and reference populations that weren't featured in the qpAdm runs in the Feldman et al. paper. I also limited the analyses to what were in my view the most proximate two- and three-way solutions in terms of chronology and geography.

The models with the best statistical fits, each labeled with their "tail probs", are available in a zip file here. From my experience with qpAdm, I'd say that the most useful models generally show comparably high tail probs but low chisq values and standard errors. Please note also that I discarded all of the models with at least one standard error higher than 0.2 and/or based on less than 100K SNPs.

As far as I can see, these two are among the very best outcomes. Bell_Beaker_FRA are nine samples associated with the Bell Beaker culture (BBC) from what is now France. Interestingly, the BBC population was rich in Y-haplogroup R1b-M269.

Levant_ISR_Ashkelon_IA1_ASH067
Bell_Beaker_FRA 0.116±0.059
GRC_Minoan 0.507±0.111
Levant_ISR_Ashkelon_LBA 0.377±0.117
chisq 9.018
tail prob 0.530432

Levant_ISR_Ashkelon_IA1_ASH068
Bell_Beaker_FRA 0.237±0.044
GRC_Minoan 0.763±0.044
chisq 4.736
tail prob 0.943265

In my opinion, these models basically confirm that both ASH067 and ASH068 harbor Yamnaya-related ancestry. It's heavily diluted and minor, but it's there. Admittedly, even after looking over the qpAdm output several times, I'm still not quite sure how their ancestors acquired this ancestry. But for the time being, Mediterranean Europe appears to be the most plausible proximate source one way or another. Any thoughts about that? Feel free to share them in the comments below.

See also...

Evidence of European ancestry in the Philistines

R1b-M269 in the Bronze Age Levant

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

Evidence of European ancestry in the Philistines

The abstract below has just appeared at the European Nucleotide Archive (see here), so I'm guessing that the relevant paper and accompanying ancient genome-wide data will be published within weeks if not days. Emphasis is mine:

The ancient Mediterranean port-city of Ashkelon, identified as “Philistine” during the Iron Age, underwent a dramatic cultural change between the Late Bronze- and the early Iron- Age. It has been long debated whether this change was driven by a substantial movement of people, possibly linked to a larger migration of the so-called “Sea Peoples”. Here, we report genome-wide data of ten Bronze- and Iron- Age individuals from Ashkelon. We find that the early Iron Age population was genetically distinct due to a European related admixture. Interestingly, this genetic signal is no longer detectible in the later Iron Age population. Our results support that a migration event occurred during the Bronze- to Iron- Age transition in Ashkelon but did not leave a long-lasting genetic signature.

Update 4/7/2019: The paper is now available at Science Advances [LINK]. One of the Ashkelon ancients, who also shows a relatively high level of European ancestry, belongs to Y-Chromosome haplogroup R1 (probably R1b-M269). I've updated my Global25 datasheets with the new samples. Look for the Levant_ISR_Ashkelon prefix. Same links as always...

Global25 datasheet ancient scaled

Global25 pop averages ancient scaled

Global25 datasheet ancient

Global25 pop averages ancient

This is how they cluster in my Principal Component Analysis (PCA) of ancient West Eurasian genetic variation. The relevant datasheet is available here. Based on these results, it's tempting to think that the European ancestry in the Philistines may have been of Greek provenance. But keep in mind that this is just a two dimensional view and a simplification of reality. I'll have more to say about the ancestry of these individuals and the origins of the Philistines in future blog posts.

See also...

Five foot Philistines

How did steppe ancestry spread into the Biblical-era Levant?

A Mycenaean and an Iron Age Iranian walk into a bar...

What do they have in common? The same type of Near Eastern ancestry? From Iran? Nope, that's a joke. Obviously, they share the same type of steppe ancestry. This probably has some very important linguistic implications.

The relevant Principal Component Analysis (PCA) datasheet is available here. Below are two pairs of formal mixture models that support my inferences from the PCA.

Mycenaean
Srubnaya_MLBA 0.266±0.029
Tepecik_Ciftlik_N 0.734±0.029
taildiff: 0.588000631
Full output

Mycenaean
Minoan_Lasithi 0.790±0.023
Srubnaya_MLBA 0.210±0.023
taildiff: 0.187709803
Full output

...

Turkmenistan_IA
Namazga_CA 0.528±0.040
Srubnaya_MLBA 0.472±0.040
taildiff: 0.561330411
Full output

Turkmenistan_IA
Dzharkutan1_BA 0.530±0.037
Srubnaya_MLBA 0.470±0.037
taildiff: 0.485083377
Full output

But seriously, what's the direct link between populations like Tepecik_Ciftlik_N/Minoan_Lasithi and Namazga_CA/Dzharkutan1_BA, except some exceedingly distant farmer ancestry from the Fertile Crescent?

See also...

An early Iranian, obviously

Graeco-Aryan parallels

Yamnaya isn't from Iran just like R1a isn't from India

Steppe admixture in Mycenaeans, lots of Caucasus admixture already in Minoans (Lazaridis et al. 2017)

Over at Nature at this LINK. Why is the presence of steppe admixture in Mycenaeans important? And why does it matter if the Minoans already had a lot of ancestry from the Caucasus or surrounds? Because Mycenaeans were Indo-Europeans and Minoans weren't. I'm still reading the paper and will update this entry regularly over the next few days. Below is the abstract and, in my opinion, a key quote. Emphasis is mine.

The origins of the Bronze Age Minoan and Mycenaean cultures have puzzled archaeologists for more than a century. We have assembled genome-wide data from 19 ancient individuals, including Minoans from Crete, Mycenaeans from mainland Greece, and their eastern neighbours from southwestern Anatolia. Here we show that Minoans and Mycenaeans were genetically similar, having at least three-quarters of their ancestry from the first Neolithic farmers of western Anatolia and the Aegean [1, 2], and most of the remainder from ancient populations related to those of the Caucasus [3] and Iran [4, 5]. However, the Mycenaeans differed from Minoans in deriving additional ancestry from an ultimate source related to the hunter–gatherers of eastern Europe and Siberia [6, 7, 8], introduced via a proximal source related to the inhabitants of either the Eurasian steppe [1, 6, 9] or Armenia [4, 9]. Modern Greeks resemble the Mycenaeans, but with some additional dilution of the Early Neolithic ancestry. Our results support the idea of continuity but not isolation in the history of populations of the Aegean, before and after the time of its earliest civilizations.

...

The simulation framework also allows us to compare different models directly. Suppose that there are two models (Simulated1, Simulated2) and we wish to examine whether either of them is a better description of a population of interest (in this case, Mycenaeans). We test f4(Simulated1, Simulated2; Mycenaean, Chimp), which directly determines whether the observed Mycenaeans shares more alleles with one or the other of the two models. When we apply this intuition to the best models for the Mycenaeans (Extended Data Fig. 6), we observe that none of them clearly outperforms the others as there are no statistics with |Z|>3 (Table S2.28). However, we do notice that the model 79%Minoan_Lasithi+21%Europe_LNBA tends to share more drift with Mycenaeans (at the |Z|>2 level). Europe_LNBA is a diverse group of steppe-admixed Late Neolithic/Bronze Age individuals from mainland Europe, and we think that the further study of areas to the north of Greece might identify a surrogate for this admixture event – if, indeed, the Minoan_Lasithi+Europe_LNBA model represents the true history.

Lazaridis, Mittnik et al., Genetic origins of the Minoans and Mycenaeans, Nature, Published online 02 August 2017, doi:10.1038/nature23310

Update 03/08/2017: This is my own Principal Component Analysis (PCA) of the Minoan and Mycenaean samples, which are freely available at the Reich Lab website here. The Armenian angle for the eastern admixture in Mycenaeans looks forced. The trajectory of this admixture obviously runs from Northern or Eastern Europe to the Minoans. If it did arrive from Armenia, then realistically only via a heavily steppe-admixed population. Right click and open in a new tab to enlarge:

Update 05/08/2017: Much like Lazaridis et al., I ran a series to qpAdm analyses to find the best mixture model for the Mycenaeans. However, just to see what would happen, unlike Lazaridis et al., I didn't group any of the archaeological populations into larger clusters based on their genetic affinities. The three models below stood out from the rest in terms of their statistical fits.

Mycenaean
Minoan_Lasithi 0.786±0.049
Sintashta 0.214±0.049
taildiff: 0.96574059
chisq: 6.030
Full output

Mycenaean
Corded_Ware_Germany 0.210±0.043
Minoan_Lasithi 0.790±0.043
taildiff: 0.961238695
chisq: 6.198
Full output

Mycenaean
Minoan_Lasithi 0.791±0.043
Srubnaya 0.209±0.043
taildiff: 0.950419642
chisq: 6.558
Full output

So it's essentially the same outcome as the one obtained by Lazaridis et al., because Sintashta and Srubnaya are part of their Steppe_MLBA cluster, while Corded Ware is part of their Europe_LNBA cluster, and it's these clusters that, along with Minoan_Lasithi, provided their most successful mixture models for the Mycenaeans. But it's nice to see Sintashta at the top of my results, because it fits so well with the long postulated archaeological links between Sintashta and the Mycenaeans (for instance, see here).

By the way, here's what I said back in May when the Mathieson et al. 2017 preprint came out (see here). So things are falling into place rather nicely.

The same paper also includes the following individual from present-day Bulgaria dated to the start of the Late Bronze Age (LBA), which is roughly when the Mycenaeans appeared nearby in what is now Greece:

Bulgaria_MLBA I2163: Y-hg R1a1a1b2 mt-hg U5a2 1750-1625 calBCE

This guy is the most Yamnaya-like of all of the Balkan samples in Mathieson et al. 2017, and, as far as I can see based on his overall genome-wide results, probably indistinguishable from the contemporaneous Srubnaya people of the Pontic-Caspian steppe. He also belongs to Y-haplogroup R1a-Z93, which is a marker typical of Srubnaya and other closely related steppe groups such as Andronovo, Potapovka and Sintashta. So there's very little doubt that he's either a migrant or a recent descendant of migrants to the Balkans from the Pontic-Caspian steppe.

See also...

A Mycenaean and an Iron Age Iranian walk into a bar...

Main candidates for the precursors of the proto-Greeks in the ancient DNA record to date

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