The genetic sequences of Japanese.

The Northeast Asian Haplogroup O2b suggests a very interesting sort of relationship between the Tungusic, Korean, and Japanese peoples. Haplogroup O2b's parent haplogroup, Haplogroup O2*, appears to have been thinly spread throughout East Asia since prehistoric times. The derived Haplogroup O2b* (M176) is found at low frequency across the populations of the whole of Greater Manchuria, including the Tungusic, Korean, Japanese, and even the Daur people, who speak a Mongolic language that has traditionally been considered to have derived from an ancient dialect transitional between the Proto-Mongolic and Proto-Tungusic languages. One major subbranch, O2b1* (P49), is shared between the Korean and Japanese populations (with a significantly higher STR diversity among the Koreans), but its distribution does not reach the Tungusic or Daur peoples to the north. Finally, the most derived subbranch, Haplogroup O2b1a (47z), is essentially restricted to the Japanese population, although it has sporadically been detected in a few individuals who reside within the extent of the erstwhile Great Japanese Empire, in which cases it is believed to represent minor admixture from male Japanese soldiers or civilians into the local populations within the last several generations; patrilineal descent from a Japanese visitor or immigrant to some of these lands during earlier historical times is another possibility. This "nested" hierarchical and region-specific distributional pattern tends to suggest the following sequence of events:

1) The M176 mutation that defines the O2b Y-chromosome lineage first arises on an ancestral O2* chromosome belonging to a man who already resides within Greater Manchuria, or who at least already belongs to a specific "proto-Tungus-Korean" tribe.

2) Sometime after the proto-Koreans have branched off from the other populations of the Greater Manchurian region, the P49 mutation that defines Haplogroup O2b1* arises in a proto-Korean male, whose lineage becomes very successful and increases in number among the prehistoric proto-Korean population.

3) One regional subgroup of the proto-Koreans distinguishes itself from the others either culturally or by physically migrating away from their proto-Korean brethren. After the split from the greater proto-Korean population is complete, the 47z mutation that defines Haplogroup O2b1a occurs in a male of this now proto-Japanese population, who produces many male descendants and increases the frequency of the O2b1a lineage among the proto-Japanese. This very specific Haplogroup O2b1a lineage now occupies about 42.5% of the total of Haplogroup O lineages, or about 22.0% of all Y-chromosomes, among the modern Japanese, which probably reflects extreme hegemony of a certain close-knit clan in the history of the Japanese people.

In addition to suggesting a phylogenetic relationship between at least a subset of the ancestors of the Tungusic, Korean, and Japanese peoples, the distribution of Haplogroup O2b and its subbranches also argues strongly against any significant intermingling of any of these peoples during historical times.