The dominant paternal lineage of East and Southeast Asia
Haplogroup O, defined by M175, is the most common Y-chromosome lineage across East and Southeast Asia, carried by a very large share of the world's population. It dominates the paternal landscape of China, Korea, Japan, mainland Southeast Asia and much of island Southeast Asia, and it spread with some of the largest agricultural expansions in human history.
Haplogroup O is overwhelmingly the dominant lineage of East and Southeast Asia. It is carried by the great majority of men in China and is very common in Korea, Japan, Vietnam, Thailand and across island Southeast Asia, extending into parts of Central and South Asia and out into the Pacific with the Austronesian expansion. In sheer numbers it is one of the most common Y lineages on Earth.
Haplogroup O is understood to have originated in East or Southeast Asia and to have expanded dramatically with the rise of agriculture in the region, particularly the farming societies of the major East Asian river valleys. Several of its branches show signatures of rapid, large-scale expansion associated with these Neolithic developments.
O divides into major branches, often labelled O1, O2 and O3 in older nomenclature (now reorganised), whose expansions are linked to specific agricultural and linguistic groups across East and Southeast Asia. Particular sublineages are associated with the spread of major population groups, and their study has illuminated the demographic history of the region.
An O result points to East or Southeast Asian paternal ancestry. Given how common and widespread the lineage is, the subclade carries most of the geographic information, so downstream SNP testing is what distinguishes, for example, a lineage tied to one regional expansion from another.
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