M2

Origins and Evolution

mtDNA haplogroup M2 is a primary South Asian branch of macro-haplogroup M, which itself derives from L3. M2 is recognized as one of the deep-rooting maternal lineages in the subcontinent and likely arose in South Asia during the Upper Paleolithic (roughly ~40–60 kya, with many studies placing a central estimate near ~50 kya). The age and internal diversity of M2 indicate an early in situ diversification after the initial post‑Out‑of‑Africa dispersal of L3-derived lineages into South and Southeast Asia.

Subclades (if applicable)

M2 comprises multiple internal branches that have been labelled in phylogenies (commonly as M2a, M2b, and further subbranches depending on the study and resolution). These subclades show geographic structure and variable frequencies across tribal and non-tribal populations of the subcontinent. The presence of several well-differentiated sublineages within M2 is consistent with long-term local evolution and demographic stability punctuated by regional expansions.

Geographical Distribution

M2 is concentrated in South Asia, with the highest frequencies and diversity observed in India (both among tribal/Adivasi groups and many caste groups), Sri Lanka (including indigenous Veddah communities), and to a lesser extent in Pakistan, Bangladesh and Nepal. M2 occurs at varying, generally lower frequencies in Himalayan foothill groups and occasionally in neighboring regions due to historical gene flow. Unlike some M-derived clades that extend broadly into Southeast Asia or Oceania, M2 is predominantly a South Asian maternal lineage with only sporadic occurrences beyond the subcontinent.

Historical and Cultural Significance

Because of its antiquity and distribution, M2 is often interpreted as marking autochthonous South Asian maternal ancestry. It is commonly found among hunter-gatherer and tribal groups (Adivasi), but also among agricultural and caste populations, indicating continuity from Paleolithic and Mesolithic foraging communities into later Neolithic and historical societies. M2 lineages therefore contribute to models of deep population continuity in South Asia and are used in studies contrasting incoming Neolithic/ Bronze Age gene flow with indigenous substrate ancestry.

Conclusion

mtDNA haplogroup M2 represents a long-standing maternal lineage in South Asia, reflecting an early colonization and subsequent regional diversification. Its internal structure and geographical patterns make it a valuable marker for reconstructing Paleolithic and later demographic processes within the subcontinent, including continuity among tribal groups and incorporation into later cultural formations.