A significant finding

At least five individuals from Neolithic burial sites in what is now Ukraine harbor ancestry that is normally associated with much later steppe populations. Labeled UKR_N_admixed in the plot below, these samples were part of the Mathieson et al. 2018 dataset and most were radiocarbon dated to well before 5,000 BCE. An interactive version of the plot is available here.

Their unusual ancestry probably explains why they form a cluster that appears to be pulling away from the ancient European hunter-gatherer cline towards the part of the plot home to RUS_Progress_En (from the Progress-2 Eneolithic burial site in the North Caucasus piedmont region). But, of course, there's more to this. For instance, consider the formal statistics-based qpAdm mixture models below:

UKR_N_admixed
RUS_Progress_En 0.083±0.021
UKR_N 0.917±0.021
chisq 7.461
tail prob 0.589238
Full output

UKR_N_admixed
RUS_Progress_En 0.172±0.021
SRB_Iron_Gates_HG 0.332±0.024
UKR_Meso 0.495±0.035
chisq 9.255
tail prob 0.321282
Full output

UKR_N_I1738
RUS_Progress_En 0.196±0.035
SRB_Iron_Gates_HG 0.414±0.039
UKR_Meso 0.390±0.056
chisq 7.913
tail prob 0.442006
Full output

Ergo, as much as a quarter of the genome of individual I1738, dated to 5473-5326 calBCE, might be derived from a population very similar to RUS_Progress_En. This is a big deal, because it's still widely believed that this type of ancestry didn't exist until the Eneolithic, and that it didn't spread significantly until the migrations of steppe pastoralists associated with the Early Bronze Age Yamnaya culture.

I'm confident, nay, certain, that my findings will be confirmed directly with more Neolithic samples from present-day Ukraine and surrounds.

See also...

Understanding the Eneolithic steppe

Ancient DNA vs Ex Oriente Lux

Mixed marriages on the early Eneolithic steppe

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...

Armenians vs Georgians

Armenians and Georgians are ethnic groups that live side by side in the south Caucasus, or Transcaucasia. By all accounts, they've both been there since prehistoric times and they're very similar in terms of overall genetic structure.

However, they speak languages from totally unrelated families: Indo-European and Kartvelian, respectively. How did this happen and might the answer lie in the small genetic differences that do exist between them?

To investigate this issue, I ran a series of qpAdm formal mixture models of present-day Armenians and Georgians using tens of ancient reference populations. To come up with as straightforward and meaningful results as possible, I constrained myself to two-way models. I then discarded the runs that produced "tail probs" under 0.1 and retained less than 400K SNPs. Only a handful of models passed muster, including these two:

Armenian
Mycenaeans_&_Empuries2 0.233±0.041
Kura-Araxes_Kaps 0.767±0.041
chisq 18.422
tail prob 0.142151
Full output

Georgian
Globular_Amphora 0.071±0.025
Kura-Araxes_Kaps 0.929±0.025
chisq 18.419
tail prob 0.142266
Full output

At the most basic level, the results suggest that both Armenians and Georgians are overwhelmingly derived from populations of Bronze Age Transcaucasia associated with the Kura-Araxes archeological culture, albeit with minor ancestries from somewhat different sources from the west. As far as I can see, when using more than 400K SNPs and a wide range and large number of outgroups (or right pops), neither Armenians nor Georgians can pass perfectly for any one ancient population in my dataset.

The best proxies for the minor but significant western ancestry in Armenians are Mycenaeans of the Bronze Age Aegean region and Greek colonists from Iron Age Iberia (Empuries2). Obviously, and perhaps importantly, these are both attested Indo-European-speaking groups. On the other hand, the very minor western ancestry in Georgians is best characterized as gene flow from Middle to Late Neolithic European farmers rich in indigenous European forager ancestry. It's practically impossible to say what language or languages these farmers spoke. How about something Kartvelian?

In any case, for me, the perplexing thing about present-day Armenians is that they harbor very little steppe ancestry. By and large, no more than a few per cent. Compare that to the currently available samples from what is now Armenia dating to the Middle to Late Bronze Age, which show ratios of steppe ancestry of up to 25%. For now, I'm guessing that what we're dealing with here is the classic bounce back of older ancestry layers that has been documented for different parts and periods of prehistoric Europe.

See also...

Early chariot drivers of Transcaucasia came from...

Catacomb > Armenia_MLBA

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