Ten Years Since the First Yamnaya Ancient DNA

Ten Years Since the First Yamnaya Ancient DNA

Ten years ago, in 2015, the first ancient DNA samples from the Yamnaya archaeological culture were published in the study by Haak et al. The discovery of R1b-Z2103 in Yamnaya caused a major sensation, as many commentators at the time expected to find R1a, whose correlation with the spread of Indo-European languages seemed self-evident.

Last year, Lazaridis et al. (2024) largely clarified the origins of Yamnaya autosomes. However, the precise origin of its main Y-DNA lineage, Z2103, remains unresolved. Yediay (2024) addressed this issue (see picture 2), noting that virtually all known cases of Z2103 found in the Eurasian steppe belong to the Z2106+ branch, while all currently known cases of basal Z2103* are found in the ancient South Caucasus.

How can this apparent contradiction be explained?

At the current stage of research, we know that Z2103 experienced a dramatic founder effect during the spread of the Yamnaya culture and was practically absent from the Pontic–Caspian steppe before the emergence of that culture around 3300 BCE. As a result, 41 out of 51 Y-DNA samples extracted from Yamnaya individuals are Z2103-positive (more than 80%). Therefore, the original homeland of Z2103 must have been close to the region where the Yamnaya culture first emerged.

Yamnaya autosomes are largely derived from the preceding CLV (Caucasus–Lower Volga) cline. The genetically closest known sample comes from near the Azov region (Krivianskiy). However, in addition to CLV ancestry, Yamnaya populations also carried extra Ukraine Neolithic Hunter-Gatherer (UNHG) ancestry and some Caucasian farmer–related ancestry. These two components significantly narrow down the possible homeland.

Previously, an infiltration of UNHG ancestry into the Krasnodar region of Russia has been observed, while the additional Caucasian farmer–related ancestry was also present in the same region. Based on this evidence, it is reasonable to assume that Z2103 began its expansion somewhere between the Azov and Caucasus regions.

Such a homeland helps explain several observations:

• The reason why all three basal Z2103* branches (Y4362, L584, PF331) are found in West Asia. Their proximity to the Caucasus likely facilitated southward migrations.

• Z2106 may also have formed near the Caucasus. Its main subbranch, R-Y503415, has been identified both south of the Caucasus and north of it.

• An initial spread from west to east would also explain why the Afanasievo culture appears almost simultaneously with Yamnaya in the Altai region. Most Afanasievo males belong to Z2108, a rare subclade today found in China. Some Z2108 lineages also remained in the Pontic–Caspian steppe, where the subclade KMS67 later expanded.

• Finally, after filling the Pontic–Caspian steppe with their settlements, Yamnaya groups moved into the Balkans, where the subbranch Z2110 is found. However, in the Balkans the most successful founder effect appears to have occurred in J2b2a-L283, another minor Yamnaya lineage originating from South Caucasian farmers.

Although this principle is not universal, a potential homeland should also be associated with a diversity of related archaeological cultures. Near the Krasnodar region we find two other cultures related to Yamnaya: Novotitorovka and the North Caucasus culture. The Novotitorovka culture is particularly noteworthy because it yielded numerous wagons similar to those discovered in Lchashen in Armenia. This further raises the possibility that the region between the Azov area and the North Caucasus is precisely where we should expect to find Y-DNA lineages ancestral to those later found in West Asia, including the still elusive I2a2b.