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Y-DNA Haplogroup Atlas

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Haplogroup I2a1b2

I2-M423

Macro-haplogroup
I
Parent clade
I2a1b
Formed (estimate)
c. 10,000–12,000 years before present
TMRCA (estimate)
c. 6,000–7,000 years ago

Overview

I2a1b2 (M423) is a major southeastern–eastern European branch of haplogroup I2 with deep roots among Mesolithic foragers of the Balkans and the Carpatho–Danubian region. Unlike the later Dinaric PH908 lineage, M423 represents an older stratum of I2 diversity that persisted through the Mesolithic and Neolithic periods and later became assimilated into a range of prehistoric and early historic populations.

Geographic distribution

Modern frequencies peak in Bosnia, Croatia, Serbia, Romania, Moldova and western Ukraine, with moderate levels in Hungary, Slovakia and Poland. Low but notable frequencies appear in Greece, Bulgaria and Turkey, reflecting prehistoric Balkan–Anatolian connectivity.

Ancient DNA

  • Multiple Mesolithic and early Neolithic individuals from the Balkans (e.g., Lepenski Vir, Iron Gates region) belong to I2-M423.
  • Early European farmers occasionally carried basal I2a1b2 lineages, indicating assimilation into expanding agricultural societies.
  • Copper and Bronze Age Balkan individuals also exhibit continuity with M423 substrata.

Phylogeny & subclades

I2a1b2 forms a sister branch to I2a1b1. While I2a1b1 underwent explosive Slavic-associated growth, M423 preserved an older and more geographically stable profile. Downstream substructure includes L161 and several local Balkan-Carpathian microclades.

  • I2-L161
  • I2-Y3104
  • Basal M423* microclades

Notes & context

Archaeogenetic studies consistently highlight I2-M423 as a foundational paternal lineage of southeastern European hunter–gatherer populations. Its persistence over millennia makes it a key lineage for reconstructing Balkan deep-time population history.