Overview
Haplogroup R-Z2120 is a key downstream branch of R-Z2113 and forms one of the main lineages that carry eastern R1b ancestry into specific regions of the Balkans and the northern Aegean. It likely arose toward the end of the Bronze Age, at a time when local Balkan populations were consolidating into more clearly recognizable tribal and regional entities. Z2120 lineages were part of the paternal background of groups that interacted with, and sometimes descended from, steppe derived R-Z2103 populations introduced earlier in the Bronze Age. Z2120 shows evidence of multiple founder events during the Iron Age and early classical periods. Its downstream clusters are often concentrated in particular valleys, coastal regions and upland zones, suggesting that it became embedded in relatively stable local communities. These lineages then persisted through the Roman, Byzantine and medieval eras, leaving a clear signal in present day southeastern European populations. Because Z2120 sits at the intersection between steppe ancestry and long term Balkan local continuity, it is an informative marker for the demographic history of the region over the last three millennia. Its presence alongside other Z2103 subclades illustrates that eastern R1b contributed in a complex and layered way to the paternal structure of southeastern Europe rather than through a single simple expansion.