Did South Caspian hunter-fishers really migrate to Eastern Europe?

The idea that most of the Near Eastern-related ancestry in the ancient populations of the Pontic-Caspian (PC) steppe is, one way or another, sourced from the territory of present-day Iran is a fairly popular one nowadays (for instance, see here). It might turn out to be correct, once there are enough relevant samples to test it properly, but in my opinion the chances of this are slim.

My skepticism is based on literally hours of analyses with the currently available ancients from the Caucaso-Caspian region, like, for instance, the admixture graphs below featuring foragers and early farmers from Russia, Georgia and Iran. The relevant qpGraph and dot files are available here.

Note that the further I move away from Eastern Europe in these graphs when looking for the source of the southern ancestry in the Eneolithic population from the southernmost part of the PC steppe (Piedmont_En), the more difficult it is for me to create a statistically sound model. What might this tell us about the provenance of this so called southern ancestry?

See also...

The PIE homeland controversy: August 2019 status report

Some myths die hard

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

Maykop: a multi-ethnic layer cake?

Let's speculate about the linguistic affinities of the currently available ancient populations from the Caucasus and surrounds. I put together a series of outgroup f3-stats to help things along. They're available for download here.

Maykop
Georgian 0.258224
Abkhasian 0.257899
Latvian 0.257376
Swedish 0.257301
Turkish_Trabzon 0.256996
Basque_Spanish 0.256589
Chechen 0.256514
Icelandic 0.256418
Norwegian 0.256325
Lezgin 0.256272
Irish 0.256227
Tabasaran 0.256092
Italian_Bergamo 0.25605
English_Cornwall 0.256032
Polish_East 0.255991
Scottish 0.255955
Adygei 0.255913

Steppe_Maykop
Latvian 0.261845
Russian_North 0.26145
Estonian 0.260355
Finnish 0.260211
Lithuanian 0.260072
Udmurd 0.259804
Ingrian 0.259663
Surui 0.259637
Vepsa 0.259608
Karelian 0.259532
Karitiana 0.259482
Russian_West 0.259397
Russian_Central 0.259274
Wichi 0.259106
Saami 0.258982
Komi 0.258945
Icelandic 0.258854
Swedish 0.258814
Mordovian 0.258604
Irish 0.25859

Eyeballing the stats might be enough to get a general impression about what they mean, but to understand them properly it's necessary to get technical with something like PAST3 (see here). That's because f3-stats pick up shared genetic drift from all drift paths, and don't especially focus on more recently shared ancestry. This can often lead to confusing outcomes.

Below are a few examples of linear models based on my f3-stats. Note that many Indo-European speakers, especially from Northern Europe, are foremost attracted to ancient samples from the Pontic-Caspian steppe. On the other hand, non-Indo-European speakers, from such far flung locations as the Caucasus and Iberia, show relatively stronger affinity to ancient samples from Anatolia and the Caucasus. Moreover, Uralic speakers show elevated affinity to ancient hunter-gatherer samples from Eastern Europe and Siberia. Makes sense, right?

Based on these and other data, I'd say that Maykop and the culturally related Steppe Maykop were something of a multi-ethnic polity, with many near and far related languages spoken by its people, including perhaps Kartvelian, Northwest Caucasian, Yeniseian and Indo-European. But it seems to me that Proto-Indo-European was spoken by steppe foragers turned pastoralists just outside of the Maykop zone. And I'm quite sure that after the Maykop collapse various early Indo-European groups pushed across the Caucasus and deep into the Near East. Just take a look at the f3-stats and linear model for Hajji_Firuz_BA to see what I mean.

See also...

An exceptional burial indeed, but not that of an Indo-European

The Steppe Maykop enigma

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

The Steppe Maykop enigma

Who were the Steppe Maykop people exactly? Their ancestry must surely rank as one of the biggest surprises served up by ancient DNA to date.

I always thought that they'd turn out roughly like a mixture between populations associated with the Kura-Araxes and Yamnaya cultures (mostly because their territory was located sort of in between them). Nope, that wasn't even close. This is where they cluster compared to Kura-Araxes and Yamnaya samples in my Principal Component Analysis (PCA) of world-wide genetic variation: the Global25.

To explore the ancestry of the Steppe Maykop people in more detail I ran a couple of unsupervised Global25/nMonte tests, using basically every ancient population in the (scaled) Global25 datasheet that seemed chronologically sensible and even remotely relevant. I narrowed things down to these two mixture models.

Steppe_Maykop
Geoksiur_Eneolithic,11.2
Piedmont_Eneolithic,44.4
West_Siberia_N,44.4
distance%=1.5161

Steppe_Maykop
Piedmont_Eneolithic,46.6
Sarazm_Eneolithic,10.4
West_Siberia_N,43
distance%=1.6408

But, you might say, Global25/nMonte isn't a published analytical method and it doesn't run on formal statistics, the meat and potatoes of ancient DNA papers. OK then, let's try the same models with the qpAdm software, which is a published method and does run on formal statistics, using exactly the same samples.

Steppe_Maykop
Geoksiur_Eneolithic 0.100±0.032
Piedmont_Eneolithic 0.433±0.053
West_Siberia_N 0.467±0.028
chisq 19.155
tail prob 0.159096
Full output

Steppe_Maykop
Piedmont_Eneolithic 0.429±0.051
Sarazm_Eneolithic 0.119±0.033
West_Siberia_N 0.452±0.026
chisq 18.090
tail prob 0.202699
Full output

They're basically identical. Importantly, my models must reflect reality at some level, because otherwise I wouldn't be able to produce a pair of essentially identical results using such vastly different statistical methods. So the pertinent question is what do these results actually mean?

It seems unlikely to me that we're dealing here with a highly complex three-way mixture process, involving populations from such far flung locations as western Siberia and southern Central Asia. Rather, I suspect that Steppe Maykop was the result of a two-way mixture between Piedmont_Eneolithic (the population that lived before it on the steppe north of the Caucasus) and someone just a little bit more easterly. I'm guessing that the latter was the (as yet unsampled) population associated with the Kelteminar archeological culture.

By the way, please note that Piedmont_Eneolithic is made up of samples from two different locations on the Piedmont steppe, and I occasionally treat them as separate populations labeled Progress_Eneolithic and Vonyuchka_Eneolithic (for instance, see here).

Update 28/02/2019: Below is a PCA focusing on West Eurasian genetic variation. Overall, the position of Steppe Maykop relative to Geoksiur_Eneolithic, Piedmont_Eneolithic and West_Siberia_N appears to reflect my nMonte and qpAdm models. However, as per our discussion in the comments, one of the Steppe Maykop individuals (the most southerly one in the PCA) probably also has recent ancestry from the Caucasus.

See also...

An exceptional burial indeed, but not that of an Indo-European

Maykop: a multi-ethnic layer cake?

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