What Happened In Bronze Age Armenia?

Davidski at his Eurogenes blog notes an interesting disconnect between ancient DNA from the early Bronze Age in Armenia (a.k.a. the Kura-Araxes culture) and the Middle Late Bronze Age in Armenia.

The early Bronze Age ancient DNA from Armenia is pretty much what you would expect:

Armenia_EBA or Kura-Araxes shows strong affinity to Caucasus populations, particularly those from the Northeast Caucasus. This is very cool, and it makes a lot of sense, because historical linguists and archaeologists generally consider Kura-Araxes people to have been early speakers of Hurrian, an ancient language thought to be closely related to present-day Northeast Caucasian languages.

Hurrian and some languages that were probably related (e.g. Hattic) were the principle languages of Anatolia and the highlands near Mesopotamia before the linguistically Indo-European Hittites came along and conquered essentially all of Anatolia, the Northern Levant and northern Mesopotamia. There is good reason to think that the Minoan language also had linguistic family ties to one or more of the non-Indo-European, pre-Hittite languages of Anatolia.

But, the Middle Late Bronze Age Armenian ancient DNA unexpectedly has strong affinities to modern day Latvian and Swedish populations. What contemporary populations could have led to these affinities in the Middle Bronze Age?

Following some statistical testing, he finds that this new component of their ancestry "may have also been closely related to the Sintashta people of the Middle Bronze Age Ural steppes, who do appear very Northern European in terms of genome-wide genetic structure. The time frame fits, so does the expansive and militaristic nature of the Sintashta Culture (see here)." His analysis finds that the Middle Bronze Age Armenians had about 20% Sintashta ancestry with the other 80% from the earlier Early Bronze Age population of the region. The link in his post recounts some of the pertinent information from a new book on the topic by David Anthony (citations in the text omitted in the quotation below):

The violent and transformative Sintashta period, 2100 to 1800 BC, saw the concentration of dispersed MBA mobile herder populations into MBA II fortified settlements east of the Urals, and this settled Sintashta phase ushered in the settled Petrovka-Alakul economy as well as the artifact and grave types of the early LBA Andronovo horizon.

...

Sintashta-Petrovka chariot-driving chiefs contacted the irrigated civilizations of Central Asia (Bactria-Margiana Archaeological Complex [BMAC]), shown at the Petrovka settlement of Tugai near Sarazm and Petrovka-style ceramics inside the walled BMAC town of Gonur. Perhaps Ural copper and steppe horses were exchanged for Asian luxury goods (textiles?) for distribution to local steppe allies. The geographic expansion of Petrovka-style sites from the southeastern Ural steppes into the Zeravshan Valley in Central Asia was the foundation for the later development of Andronovo styles across Kazakhstan.

...

After the formation of the almost pan-continental Srubnaya-Andronovo cultural horizon, beginning around 1900 to 1800 BC, innovations that included bronze casting, chariotry, and some aspects of pastoral subsistence and settlement types began to diffuse between regions that had formerly appeared materially isolated, encouraging the movement of commodities such as copper, tin, and horses and enabling the more patchy diffusion of cultural traits, including language, rituals, and packages of distinctive elite behaviors. At its eastern end, the Andronovo network interacted across the Tien Shan with what is today northwestern China during the rise of the earliest Chinese state in the late Quijia, Erlitou, and early Shang periods and with Central Asia during the declining centuries (1800–1600 BC) of the BMAC and Namazga VI cultures.

The Sintashta culture population's ancient DNA as a source for the Middle Bronze Age demographic shift in Armenia is preferred in statistical comparisons relative to other candidate populations which he labels Potapovka, Corded Ware from Central Europe, Poltavka, Andronovo and Srubnaya populations.

This part of the world was not literate in this era, so there is no historical record of a major invasion or conquest as far as Armenia by chariot driving warriors from the Ural Steppes, and there isn't really any strong archaeological pointer to this significant population upheaval. But, the ancient DNA evidence and what we do know about the archaeological cultures in existence at the time certainly supports Davidski's inference.

This also suggests that one of the reasons that people in the Caucasus mountains look more Northern European than you would expect, for example, from comparing them to nearby Iranians, is that a significant share of them received a significant infusion of Northern European ancestry in the Middle Bronze Age.

This Middle Bronze Age event would also be a plausible historical moment for a language shift from Hurrian or a related language to an Indo-European language such as an early version of the Indo-European Armenian language.