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Y-DNA Haplogroup Atlas

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Haplogroup I3i

I3-Y18515

Macro-haplogroup
I
Parent clade
I3
Formed (estimate)
c. 24,000–29,000 years before present
TMRCA (estimate)
c. 13,000–16,000 years ago

Overview

I3i (Y18515) is a rare Upper Paleolithic branch of haplogroup I3 that most likely formed within highland West Asian populations along the arc connecting the eastern Taurus, northern Mesopotamia and the central Zagros. Its deep time depth indicates survival through the Last Glacial Maximum in a patchwork of refugial habitats, followed by low level persistence into the early Holocene. I3i represents one of the oldest surviving paternal layers in the region, preserved at very low frequencies among later Neolithic and Bronze Age populations.

Geographic distribution

Modern carriers of I3i are extremely sparse and are found primarily in southeastern Turkey, northern Iraq, western Iran and occasionally northern Syria and Armenia. Isolated occurrences in diaspora communities around the eastern Mediterranean reflect recent historical movements rather than independent diversification centers.

Ancient DNA

  • Upper Paleolithic and Epipaleolithic individuals from the Zagros and northern Mesopotamia show Y chromosome variation compatible with deep I3 related diversification events in this region.
  • Pre Pottery Neolithic remains from the northern Fertile Crescent display basal West Eurasian paternal lineages, among which clades such as I3i would fit in age and phylogenetic position.
  • Chalcolithic and Bronze Age genomes from the northern Mesopotamian and Zagros foothill zones retain components that can be modeled as mixtures of incoming farmer and steppe ancestries with older highland substrata similar in profile to the I3 complex.

Phylogeny & subclades

Within haplogroup I3, I3i forms a sister branch to other deep sublineages such as I3d, I3e, I3f and I3g. The defining SNP Y18515, together with markers like Y18518 and BY18601, delimits a very small cluster with minimal internal radiation. This phylogenetic pattern is consistent with long term survival in small, geographically constrained populations.

  • I3-Y18518
  • I3-BY18601
  • Basal I3i* lineages

Notes & context

Although numerically rare, I3i is important for anchoring the early diversification of haplogroup I3 in highland West Asia. Its deep age, restricted distribution and minimal branching add weight to models that emphasize the role of Near Eastern mountain refugia in preserving ancient paternal diversity.