Overview
Haplogroup R2b is a rare and deeply rooted branch under the broader R2 lineage. Whereas R2a underwent substantial diversification across South Asia, R2b represents an early diverging and extremely ancient lineage that retained a geographically narrow footprint. Formed during the Late Upper Paleolithic, R2b likely originated somewhere between the Iranian Plateau and southern Central Asia. Its internal structure indicates long term survival within small, isolated founder groups rather than broad demographic expansion. Unlike R2a, which spread widely among Neolithic and Bronze Age populations of India, Pakistan and Iran, R2b displays a very restricted distribution. Its rarity suggests that it persisted among small communities, possibly pastoral or agro-pastoral, that did not participate in the major population expansions of the region. This makes R2b exceptionally valuable for reconstructing early human population structure in Southwest and South Central Asia. Genetic signals associated with R2b are occasionally detected in mountainous regions, supporting the idea that geographical isolation played a major role in the survival of this lineage. Today, R2b is found only at very low frequencies, predominantly in Iran, Afghanistan and occasionally Pakistan or Central Asian highland populations. Its limited visibility in modern datasets contrasts sharply with its significant phylogenetic age, hinting at a long and complex demographic history shaped by repeated bottlenecks and localized continuity.