M7B

Origins and Evolution

Haplogroup M7B is a subclade of the broader mtDNA haplogroup M7, itself a derivative of macro-haplogroup M. Based on phylogenetic position and coalescent age estimates for M7 and its sublineages, M7B likely arose in East to Southeast Asia during the Late Pleistocene (on the order of ~20 thousand years ago, recognizing uncertainty in mutation-rate calibrations). As an intermediate clade within the M7 phylogeny, M7B connects upstream diversity in M7 with downstream, geographically structured daughter lineages that diversified during the terminal Pleistocene and Holocene.

Subclades

M7B contains multiple downstream branches (often labeled in literature as M7b1, M7b2, etc., and finer sublineages such as M7b1a in high-resolution studies). Some subclades of M7B show strong geographic structure: for example, certain M7b1-derived lineages are relatively common among populations linked to Austronesian-speaking groups and some island populations in the western Pacific, while other M7B subbranches are concentrated in mainland southern China and neighboring regions. High-resolution sequencing (complete mtGenome data) is required to resolve and name many of these subclades precisely; research to date indicates heterogeneity reflecting both deep Paleolithic splits and later Holocene expansions.

Geographical Distribution

M7B is best documented in East Asia and Southeast Asia, with highest frequencies in southern Chinese populations and detectable presence in Japan (including Ryukyu), Korea, Taiwan (including indigenous groups), and across parts of mainland Southeast Asia and island Southeast Asia. The distribution pattern suggests an origin on the East Asian mainland with subsequent dispersals into adjacent island groups during the Holocene.

Historical and Cultural Significance

Because M7B and its descendants span a timeframe from the Late Pleistocene into the Holocene, they record multiple demographic processes: Paleolithic settlement of East Asia, post-glacial north–south redistributions, and later Neolithic/Holocene population movements. Certain M7B-derived lineages appear enriched in populations associated with the Austronesian expansion, linking maternal ancestry signatures to the maritime dispersals from Taiwan and southern China into Island Southeast Asia and the western Pacific. Other M7B branches likely reflect continuity in southern China and nearby regions from Paleolithic and early Holocene inhabitants.

Conclusion

M7B is an informative maternal lineage for studies of East and Southeast Asian prehistory. It occupies an intermediate phylogenetic position within M7 and displays geographic structuring that corresponds to both deep Paleolithic ancestry and later Holocene dispersals (including Austronesian-related movement). Continued sampling and full mitogenome sequencing across understudied populations (especially in southern China, Taiwan, and island Southeast Asia) will refine the chronology and migratory events recorded by M7B subclades.