Dear Iosif...

Update 29/08/22: Dear Iosif #2

...


I'm skimming through the Lazaridis, Alpaslan-Roodenberg et al. paper that just came out at Science. And I feel like someone punched me in the face.

Nevertheless, I'll try to be diplomatic. Suffice to say, for now, that there's some rather strange stuff in this paper.

The main problem is that the authors are attempting to study fine scale ancestry with a somewhat rough distal model. As a result, they miss important details.

For instance, this quote is from the paper's supplementary PDF file, freely available here.

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.

Obviously, EHG means Eastern European Hunter-Gatherer. But why focus on EHG? Surely, this makes little sense when looking at the genetic prehistory of West Asia, because no one ever argued that this region was settled by EHG populations. It was widely settled by Yamnaya-related groups, with already heavily diluted EHG ancestry, during the metal ages.

OK, so the authors are actually aware about the potential dilution of EHG ancestry, but they don't really do anything about it.

If we're looking at the origins of West Asian R1b-M269, and using its association with autosomal DNA components as a guide, then we should be focusing on Yamnaya-related ancestry.

For instance, here's a fine scale ancient ancestry model based on Principal Component Analysis (PCA) data. It shows the ancestry proportions of two relatively high coverage Iron Age males from two different sites in Iran from the Lazaridis, Alpaslan-Roodenberg et al. dataset. Both belong to R1b-M269 and both show significant Yamnaya-related ancestry.

Target: IRN_HajjiFiruz_IA:I2327_all
Distance: 2.2930% / 0.02292994
39.6 Kura-Araxes_ARM_Kaps
24.2 IRN_Ganj_Dareh_N
18.2 Levant_PPNB
12.4 Yamnaya_RUS_Samara
4.4 Anatolia_Tepecik_Ciftlik_N
1.2 Han

Target: IRN_Hasanlu_IA:I4232_all
Distance: 2.5179% / 0.02517895
26.0 IRN_Ganj_Dareh_N
25.6 Kura-Araxes_ARM_Kaps
24.4 Anatolia_Tepecik_Ciftlik_N
15.8 Yamnaya_RUS_Samara
7.6 Levant_PPNB
0.6 IRN_Shahr_I_Sokhta_BA2

As a control, here's an earlier, Chalcolithic sample bearing Y-haplogroup J2b from the same region. Not surprisingly, this individual totally lacks the Yamnaya-related signal.

Target: IRN_HajjiFiruz_ChL:I4241_all
Distance: 2.7938% / 0.02793782
32.6 Kura-Araxes_ARM_Kaps
25.6 IRN_Ganj_Dareh_N
23.6 Anatolia_Tepecik_Ciftlik_N
18.2 Levant_PPNB

Overall, these results make perfect sense. I could probably locate very minor signals of EHG ancestry in the Iron Age samples, but that would be more difficult and much less certain, so I won't bother.

Soon I'll be able to rerun these analyses with Bronze Age samples from Dagestan and surrounds. That should bump up the levels of Yamnaya-related ancestry and improve the statistical fits (wink, wink, nudge, nudge).

Disappointingly, Lazaridis, Alpaslan-Roodenberg et al. go so far as to suggest that R1b-M269 may have originated in West Asia.

However, considering the scores of ancient Eastern European populations rich in R1b-M269 and many near and far related subclades of R1b, this makes no sense whatsoever.

Indeed, contemplating nowadays that R1b-M269 might be native to West Asia, where R1b only starts showing up in the ancient DNA record during the Copper Age, is about as stupid as claiming that gravity doesn't exist.

Largely due to their distal model approach, Lazaridis, Alpaslan-Roodenberg et al. also argue that the Indo-Anatolian homeland was located in what is now Armenia and surrounds. I'm far from convinced that this solution will stand the test of time.

In terms of the more widely accepted theory that the Indo-Anatolian homeland was located on the Pontic-Caspian steppe in Eastern Europe, the most important samples in the paper are the three Bronze Age individuals from Yassitepe in western Anatolia. That's because they're from a region that is traditionally seen as the entry point of Indo-Anatolian speakers into Anatolia from the European steppe via the Balkans.

Interestingly, individual I5737, dated to 2035-1900 calBCE or the Middle Bronze Age, belongs to Y-chromosome haplogroup I2a-P78, which surely must be a signal of European ancestry. I see this as a significant result.

Here's how the trio from Yassitepe look in my fine scale ancient ancestry model. Minor Yamnaya-related ancestry does show up, although, admittedly, it might just be noise in individual I5735.

Target: TUR_Aegean_Izmir_Yassitepe_MBA:I5737
Distance: 2.7507% / 0.02750748
58.4 Anatolia_Barcin_N
20.4 Kura-Araxes_ARM_Kaps
9.2 Anatolia_Tepecik_Ciftlik_N
5.6 IRN_Ganj_Dareh_N
3.8 Yamnaya_RUS_Samara
2.6 Levant_PPNB

Target: TUR_Aegean_Izmir_Yassıtepe_EBA:I5733
Distance: 2.7969% / 0.02796887
52.0 Anatolia_Barcin_N
27.2 Kura-Araxes_ARM_Kaps
8.6 Levant_PPNB
6.2 Yamnaya_RUS_Samara
6.0 IRN_Ganj_Dareh_N

Target: TUR_Aegean_Izmir_Yassıtepe_EBA:I5735
Distance: 3.1270% / 0.03127009
36.0 Kura-Araxes_ARM_Kaps
32.4 Anatolia_Tepecik_Ciftlik_N
26.0 Anatolia_Barcin_N
2.8 IRN_Shahr_I_Sokhta_BA2
1.2 Yamnaya_RUS_Samara
1.0 Levant_PPNB
0.6 MAR_Taforalt

This isn't much, especially considering it's already late 2022, but it's better than nothing. Fortunately, more samples from Bronze Age western Anatolia are on the way (wink, wink, nudge, nudge).

However, I'm not done with the Lazaridis, Alpaslan-Roodenberg et al. dataset yet. I'm planning to spend much more time on this blog in the coming weeks and months and will be using their samples in a wide range of analyses.

Citation...

Iosif Lazaridis, Songül Alpaslan-Roodenberg et al., The genetic history of the Southern Arc:A bridge between West Asia and Europe, Science 377, eabm4247 (2022)

See also...

Dear Iosif #3

But Iosif, what about the Phrygians?

Dear Iosif, about that ~2%

Dear Iosif...Yamnaya