The possible steppe connection and Indo-European affiliation of the Trialeti-Vanadzor culture has been known for a long time. However, its partial presence in the lands which in antiquity became known as Iberia and Caucasian Albania was a hindrance to accepting and promoting that theory. Today, ancient DNA allows us to better understand population shifts in the past and resolves these apparent contradictions.
The first Y-DNA chart is based on the data from the Skourtanioti 2024 paper. A single Y-DNA sample from western Georgia was not included in the chart. The LBA-EIA (1500-800 BC) period is known in eastern Georgia as the Lchashen-Tsitelgori culture. The Y-DNA distribution from this period is very similar to that from Armenia, with a predominance of R1b and I2, which expanded during the Middle Bronze Age Trialeti-Vanadzor culture period. The two J2 samples are from the Bazaleti site, which was north of Mtskheta, close to the foothills of the Greater Caucasus range. One of them also had low steppe ancestry in autosomes, indicating the northern border of Trialeti-Vanadzor culture's impact. This corresponds to the geography of the region, dividing lowlands and highlands. (see the map)
A single G2a1 in the LBA suggests that the Kura-Araxes culture of central regions of Georgia could have a different Y-DNA structure than those from Kakhetia, who were predominantly J1.
In the Iron Age 2 (800-600 BC), the data size is small, with only one Y-DNA sample, which is G2a1.
The Early Antique period (600-300 BC) roughly corresponds to the formation of the Achaemenid Empire. R1a appears in both Georgia and Armenia, and we see a significant change in the Y-DNA distribution. G2a1 and an as-yet unknown branch of J2 (most likely a subclade of CTS900) are now the most important haplotypes. Unlike in Armenia, which during this period shifted south, in Georgia we can expect a different shift. Unfortunately, the qpAdm models from the paper do not have enough resolution to understand the possible direction of the shift. A familial grave from Bragdzor near the Shnogh village close to modern Armenian-Georgian border can provide a hint about the nature of the population that expanded in Iron Age east Georgia.
Three samples from Bragdzor were related to each other. The father and his brother had the same Y and mito DNA, J2 and K1a4c respectively. The Bragdzor father had very different autosomes compared to the contemporary Lchashenians. He is marked as an outlier in the AADR dataset. He had high CHG and virtually no steppe ancestry, similar to modern West Georgians, with no admixture from the Etiuni-Lchashen people. This indicates that he arrived in Bragdzor during his lifetime, around 800 BC. Incidentally, this date corresponds to the proposed age of separation of Georgian and Zan. Two languages usually separate when the geographic distance between them increases, typically as a result of migration.
Another indirect piece of evidence that the Bragdzor father and his brother were new migrants is the fact that his son's mother (most probably his wife buried in the same grave) was an Etiuni woman, suggesting that they did not have women from the same ethnic group when they arrived. In any case, the Bragdzor family did not leave a lasting genetic impact in northern Lori. Numerous samples from the same region in succeeding periods show no evidence of significant change.
On the other hand, the kinsmen of the Bragdzor father left an important impact in eastern Georgia, laying the foundation of Proto-Iberia, which became known as Iberia in the Hellenistic period. There are two other samples outside of Georgia with possible Kartvelian affiliation having similar autosomes to Bragdzor: one from Keti (G2a1, ~650BC) and another from Hellenistic-era Samsun. This latter was in most likelihood related to Zan people. All of them have high CHG, differentiating them from possible Caucasian Albanian sample who had Zagros Neolithic ancestry and lower CHG.
In conclusion, steppe migrants that arrived from north of the Caucasus 4500 years ago left an important impact in the South Caucasus that lasted until the Iron Age. In the Iron Age, multiple unrelated events resulted in significant changes. Near the Greater Caucasus range, mountainous people moved to the lowlands, and Iberia and Caucasian Albania formed. Meanwhile, in historic Armenia, Urartu's and the Orontid (Yervandunis) efforts to create centralized states resulted in a different change in the genetic profile. Most likely, the Achaemenid Empire also played a role in these genetic shifts in the South Caucasus, but the scant data do not permit to have definitive conclusions.
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