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Y-DNA Haplogroup Atlas

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Haplogroup G1b

G-Z30729

Macro-haplogroup
G
Parent clade
G1
Formed (estimate)
c. 18,000–22,000 years before present
TMRCA (estimate)
c. 8,000–12,000 years ago

Overview

G1b is the rare sister-branch of the dominant G1a radiation. It represents a very old but extremely low-frequency lineage whose surviving diversity is centered in the southern Caucasus, northwest Iran and isolated points across the Near East. G1b appears to have experienced long-term contraction during the Holocene, retaining only minimal regional pockets rather than undergoing the Bronze and Iron Age expansions typical of G1a. As one of the earliest diverging branches within haplogroup G1, G1b functions as a genetic fossil, preserving a Paleolithic layer of Iranian–Caucasian paternal ancestry. Its rarity in both ancient and modern DNA highlights the uneven demographic trajectories of G1’s internal branches.

Geographic distribution

G1b is found in very low frequencies across Armenia, Azerbaijan, northwest Iran and isolated individuals in Turkey. Rare instances appear among Levantine populations and a few Central Asian individuals, likely due to historic admixture rather than deep-time continuity. Because of its rarity, its geographic signature is highly fragmented but generally confined to the broader Iranian–Caucasian region.

Ancient DNA

  • A small number of Bronze Age individuals from northwest Iran carry upstream G1 markers compatible with early G1b branches.
  • Some southern Caucasus prehistoric samples show basal G1 signals, but definitive G1b calls remain limited due to low coverage.
  • No European ancient DNA assigned to G1b, consistent with its absence from Neolithic expansions.

Phylogeny & subclades

G1b branches directly from the early G1 split, forming a structurally simple lineage with several microclades resolved only by whole-genome sequencing. These subclusters exhibit limited diversification, consistent with long-term small population sizes. G1b’s phylogeny is essential for anchoring the early structure of G1 and testing models of Paleolithic refugia in the Iranian–Caucasus region.

  • G1b* basal
  • Iranian–Caucasus microclades
  • rare WGS-defined branches

Notes & context

Although numerically minor, G1b is crucial for reconstructing the deepest splits in G1 and for understanding how some Paleolithic lineages survived only in restricted highland refugia while others (e.g., G1a) participated in major Bronze and Iron Age expansions.