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 hundreds 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 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…
Steppe ancestry in Chalcolithic Transcaucasia (aka Armenia_ChL explained)
Catacomb > Armenia_MLBA
Late PIE ground zero now obvious; location of PIE homeland still uncertain, but…

Source