Overview
G2b (M377) is a distinctive, geographically constrained and historically intriguing branch of haplogroup G2. Unlike G2a—which became the dominant paternal lineage among Neolithic farmers—G2b remained restricted mainly to West and Central Asia, where it forms rare but sharply concentrated microclades. Its unique distribution has been noted in populations of the Fertile Crescent, Iran, Pakistan and occasionally among certain Jewish, Afghan and Central Asian groups.
The lineage likely reflects early Holocene highland societies, followed by multiple localized founder events rather than large-scale expansions. Its rarity in ancient DNA contrasts sharply with the abundance of G2a lineages, suggesting different ecological, cultural or demographic trajectories.
Geographic distribution
Modern G2b occurs sporadically across a wide but discontinuous region: Iran, Afghanistan, Pakistan, northern India, parts of the Levant, and at low levels in Central Asia. A subset of G2b subclades is noted among certain Jewish groups—likely due to historical founder effects within diasporic populations.
G2b is rare in Europe and the Caucasus, and when present usually reflects relatively recent historical movements.
Ancient DNA
- No firmly confirmed ancient DNA samples have been assigned to G2b, likely reflecting its historically low frequencies.
- Indirect evidence places its early formation in the highland zones east of Mesopotamia during the Upper Pleistocene.
- Some early Iron Age and historic individuals from the Iranian Plateau show upstream markers compatible with G2b ancestry, though full calls are lacking.
Phylogeny & subclades
G2b divides into several small and geographically distinct microclades, often tied to endogamous or clan-based groups in West or South Asia. Its basal diversity suggests an early East-West split between Iranian-centered branches and Pakistan–Afghanistan-centered clades.
Compared to G2a, the phylogeny of G2b is much less complex, reflecting localized expansions rather than broad Neolithic dispersals.
- G2b* basal
- G2b1 (regional clusters in West Asia)
- G2b2 (South/Central Asian branches)
- population-specific microclades
Notes & context
G2b highlights the diversity of demographic outcomes within haplogroup G: while G2a became a continental expansion lineage, G2b remained regionally constrained and reflects deeper, more localized histories. For the atlas, G2b helps illustrate the contrast between major Neolithic expansion lineages and parallel, less expansive branches of the same ancestral trunk.
References & external links