M7B

Origins and Evolution

mtDNA haplogroup M7b is a primary branch of the East Asian haplogroup M7, itself derived from macro-haplogroup M. Phylogeographic and molecular clock analyses place the diversification of M7 in southern China during the Upper Paleolithic (~30 kya), with the M7b branch coalescing later, plausibly during the Late Pleistocene (roughly ~20 kya). The pattern of internal diversity and geographic gradients in haplotype variability are consistent with a southern Chinese or nearby coastal East Asian refugium during the Last Glacial Maximum followed by northward and eastward postglacial expansions.

Genetic studies indicate that M7b split into multiple sublineages during the Late Pleistocene and Holocene. Some subclades expanded regionally in response to climate amelioration after the LGM and to demographic processes associated with the spread of coastal Neolithic economies and later maritime dispersals.

Subclades (if applicable)

M7b contains several downstream lineages (for example, clades often labelled M7b1, M7b2 and further derivatives). Particular sublineages within M7b (notably some M7b1-derived clades) have been identified at elevated frequencies in Austronesian-speaking populations and in some Japanese island groups, implying subclade-specific demographic histories. These descendant clades appear to have experienced Holocene expansions — some tied to the spread of agriculture and coastal foraging communities, and others to later island-to-island dispersals associated with Austronesian migrations.

Geographical Distribution

M7b is principally an East and Southeast Asian maternal lineage. Modern frequency peaks are typically observed in southern China and extend through mainland Southeast Asia (Vietnam, Thailand, Laos) into island regions including Taiwan, the Philippines and parts of Indonesia. M7b and its sublineages are also present in Japan (including Ryukyuan and some Jomon-descended groups) and at moderate frequencies in Korea. The distribution shows a latitudinal cline and island/coastal enrichment consistent with coastal refugia and maritime movements. Low-frequency occurrences are reported in some inland East Asian and Tibeto-Burman-speaking populations, reflecting either ancient shared ancestry or later gene flow.

Ancient DNA studies have recovered M7b-lineage haplotypes in Holocene archaeological contexts in East and Southeast Asia, supporting continuity of these maternal lineages in the region through the Neolithic and later prehistoric periods.

Historical and Cultural Significance

The demographic movements reflected by M7b likely include both postglacial recolonization of East Asia and Holocene expansions associated with the spread of Neolithic subsistence strategies (for example, rice cultivation spreading northward from Yangtze Basin source areas) and later Austronesian maritime dispersals that carried particular M7b sublineages into Taiwan, the Philippines and island Southeast Asia. In Japan, some M7b subclades are found among populations with Jomon-related ancestry as well as in groups affected by subsequent Yayoi and later migrations, making M7b informative for disentangling layered maternal ancestries in island East Asia.

Because mtDNA traces strictly maternal lines, M7b is often used alongside other mitochondrial markers and autosomal data to reconstruct sex-biased demographic events (for example, coastal female-mediated expansions) and to understand how maternal lineages moved with or independently of cultural packages like rice agriculture and seafaring technologies.

Conclusion

mtDNA haplogroup M7b is a locally rooted East Asian maternal lineage that diversified in the Late Pleistocene and expanded through multiple Holocene processes. Its regional subclade structure and geographic distribution make it a valuable marker for studying postglacial recolonization, Neolithic demographic changes in the Yangtze–coastal corridor, and Austronesian-related maritime dispersals into island Southeast Asia and parts of Japan. Continued sampling and ancient DNA retrieval are refining the timing and pathways of M7b’s spread across East and Southeast Asia.