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Y-DNA Haplogroup Atlas

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Haplogroup I3g

I3-Y18140

Macro-haplogroup
I
Parent clade
I3
Formed (estimate)
c. 24,000–28,000 years before present (estimate)
TMRCA (estimate)
c. 13,000–15,000 years ago (estimate)

Overview

Haplogroup I3g (Y18140) is a deeply divergent branch of the I3 lineage preserved at low frequencies in populations inhabiting the contact zone between the Caucasus foothills, eastern Anatolia and northern Mesopotamia. Its time depth points to an origin around or shortly after the Last Glacial Maximum, when highland West Eurasia contained multiple semi-isolated refugial populations. I3g represents one such paternal line that survived climate oscillations and later became incorporated into early Holocene forager and proto-farming groups.

Geographic distribution

Modern carriers of I3g are rare but have been documented in eastern Turkey, northern Iraq, western Iran, Armenia and parts of Georgia and Azerbaijan. Very low-level presence in Levantine and Anatolian diaspora communities likely reflects recent historical migrations rather than independent centers of diversity.

Ancient DNA

  • Upper Paleolithic and Epipaleolithic genomic samples from the Caucasus and eastern Anatolia show paternal signals consistent with deeply branching West Eurasian lineages like I3g.
  • Pre-Neolithic and early Neolithic individuals from the northern Fertile Crescent exhibit Y chromosome variation that includes basal I and J-related clades, within which the I3 complex is positioned.
  • Later Neolithic and Chalcolithic genomes from the Armenian Highlands and northern Mesopotamia contain ancestry components that can be modeled as mixtures of incoming farmer groups and older highland substrata, where lineages such as I3g would have persisted.

Phylogeny & subclades

I3g branches alongside I3a, I3b, I3c, I3d and I3e, forming one of several very old but sparsely distributed sublineages within I3. The defining SNP Y18140 and associated markers Y18142 and FGC5660 delineate a tight cluster with limited internal radiation, a pattern typical of lineages that remained confined to relatively small populations in rugged terrain.

  • I3-Y18142
  • I3-FGC5660
  • Basal I3g* lineages in the highland Near East

Notes & context

I3g is important for understanding the deep-time demographic structure of the highland Near East. Its existence supports a model in which multiple small paternal lineages survived in ecological refugia and later contributed low-level ancestry to Neolithic and Bronze Age populations without ever becoming numerically dominant.