The Middle Bronze Age (2400-1500BCE) in South Caucasus

The Middle Bronze Age (2400–1500 BCE) in the South Caucasus

Now that the DNA files from the Skourtanioti et al. (2025) paper on Georgia and the South Caucasus are available, we can examine them more closely. The focus of this thread is the crucial period of the Middle Bronze Age (MBA), when new Y-DNA lineages of steppe origin (R1b-Z2103, I2a2b) appeared in the South Caucasus and throughout historic Armenia.

The MBA data from Georgia show that only eastern Georgia was affected by steppe migrants. The blue dots indicate sites where steppe ancestry and steppe-associated Y-DNA were present, while the red dots mark sites where they were mostly absent. The second chart presents the same pattern numerically. This distribution is possible only if steppe migrants crossed the Caucasus via Dagestan and the eastern Caucasian passes.

Theoretically, migration through the Central Caucasus is also possible; however, in that case, the migrants would likely have acquired additional CHG (Caucasus Hunter-Gatherer) ancestry, which is not observed. On the contrary, MBA samples from both Georgia and Armenia show an additional shift toward Anatolian farmers. This shift is possible only if the migrants crossed what is now Azerbaijan, where an Anatolian farmer–rich population had been present since at least the Late Chalcolithic and apparently persisted into the Early Bronze Age.

This scenario explains two key findings of the paper:

1. The reason why the average steppe ancestry is lower in MBA Georgia than in MBA Armenia. This difference is due to geographic heterogeneity. Western Georgia, which lacked or had very low levels of steppe ancestry, likely harbored a non–Indo-European population, almost certainly Kartvelian tribes.

2. The paper also notes an excessive shift toward Anatolia during the MBA. This can be explained by migration through regions inhabited by Anatolian-shifted populations. The most plausible candidate is the Leyla-Tepe culture in what is now the Republic of Azerbaijan, which may also explain the presence of haplogroup E1b in MBA Armenia.

P.S. Thanks to Tigran Sg for providing the labeled G25 coordinates and for first identifying this pattern.