Overview
Haplogroup I2-Y3120 is a dominant Dinaric and South Slavic associated branch of the I2a1b-M423 lineage. It formed as part of a longer chain of upstream expansions beginning with I2a-L621 and I-CTS10228 and represents a major founder event that took place in or near the Carpathian and western Balkan regions during the late Bronze Age or early Iron Age. Today, I2-Y3120 is one of the most characteristic paternal lineages of South Slavic speaking populations and has been implicated in several debates on the demographic impact of medieval Slavic migrations.
Geographic distribution
I2-Y3120 reaches its highest present day frequencies in Bosnia and Herzegovina, Croatia, Serbia, Montenegro and western Bulgaria, often exceeding 40 percent of males in certain local populations. High frequencies are also observed in parts of Slovenia, North Macedonia and Kosovo. Outside the western Balkans, the clade is well represented in western Ukraine, southeastern Poland and Belarus, indicating a deeper Carpathian and forest steppe connection. It occurs at lower levels across the rest of Europe and in diasporic communities in the Americas and elsewhere.
Ancient DNA
- Ancient DNA studies demonstrate that the broader I2a-L621 and CTS10228 lineages expanded during the Bronze and Iron Ages in eastern and southeastern Europe, with Y3120 representing a late and strongly bottlenecked descendant branch.
- Medieval individuals associated with South Slavic and Byzantine contexts, including remains from the Balkans and northwestern Anatolia, have been assigned to I2-Y3120 and closely related subclades.
- Genomes from the Hungarian conquest period in the Carpathian Basin reveal I2-Y3120 subclades among elite burials, sometimes in combination with eastern Eurasian maternal lineages, highlighting complex interaction between steppe derived elites and local Balkan and Carpathian populations.
Phylogeny & subclades
I2-Y3120 sits at the end of a well defined series of upstream nodes: I2-M438 > I2a-L460 > I2a1b-M423 > I2a1a2b-L621 > I-CTS10936 > I-CTS4002 > I-CTS10228 > I-Y3120. The clade itself has split into several major daughter branches, including I-S17250, I-PH908, I-Y18331 and I-Z17855, which show partly overlapping but distinct geographic patterns between the central and eastern Balkans, the western Balkans and the Carpathian arc.
- I2-S17250
- I2-PH908
- I2-Y18331
- I2-Z17855
- Additional regional microclades within the Y3120 complex
Notes & context
I2-Y3120 has become a focal point in population genetic and historical discussions about the origin and expansion of South Slavic groups. Modern frequency peaks in the Dinaric Alps and high diversity in the Carpathian and western Balkan regions suggest that both areas played important roles in the clade's demographic history. While older hypotheses considered I2a in the Balkans to be a purely pre Slavic Paleolithic survival, current evidence indicates that Y3120 itself is the product of a much later Iron Age founder event, followed by strong growth during the early medieval spread of Slavic languages.
References & external links