Shinoda: In contrast to the way in which mitochondrial DNA is inherited matrilineally, Y-chromosomes are passed on only from father to son. The biggest mystery over Japanese people’s Y-chromosomes is that although 30% of people in the Japanese archipelago possess the so-called D type, it is hardly found at all outside of Japan. As a result of the fact that integration went well in the Japanese islands, it’s conceivable that the genes of the Jomon people have remained as they were until this day, but why is it that they only remained in the Japanese archipelago and vanished from the continent?
Miura: The reason for that is probably that there were no conquests or large-scale massacres in the Japanese islands.
Shinoda: Usually, when you talk about conquests, in many cases the men are killed and the women are turned into slaves, and it’s usual for the Y-chromosome line of the conquered people to end. Because that didn’t happen, it means that an extremely diverse culture blending both Jomon and Yayoi elements should have been passed on in Japanese culture.
Miura: Even in the Kojiki, it’s told that the annihilated losing side gave terms and conditions, promising that if the victors defended the palace properly that they wouldn’t “haunt” them, that they would “be at peace” and so on. It was because of this that the imperial family, the victorious side and so on achieved reconciliation—of sorts—by deifying the losers.
If it was the history of another country, it would be normal to uproot and fully beat-down and eradicate the other side. But in the Kojiki, Amaterasu of the Yamato line and Susanoo of the Izumo line are made out to be older sister and younger brother, and are in a plot setting where they both have the same roots. This was probably one contrivance devised for the purpose of seeking conciliation between the ethnic groups.
The late historian Amino Yoshihiko advocated the theory that “the differences in accent/intonation between the Kansai (western) and Kanto (eastern) dialects of Japanese have existed since the Jomon period,” but the Japanese language is not at all similar to either Korean or Chinese. It’s said that this is because Yayoi culture incorporated the Jomon language into it.
Shinoda: It has been spoken of in the past as if there was a single, unified “Jomon language,” but if we consider the diversity of the Jomon period then surely it’s more natural to think that there were a number of different languages. It’s probably the case that the Japanese language was created through the intermixing of those languages and the further incorporation of the Yayoi people’s language.
It’s a topic for future research, but I think that the process of how the transition from Jomon to Yayoi took place is a point that really needs to be unraveled, because I think that period was the most important time for the creation of the Japanese people and Japanese culture.
I believe that the coming of the Yayoi people was not just one single occurrence; that it was precisely because they didn’t all suddenly come along in one go that a forceful conquest did not take place. My guess is that first of all there was a group that came in from the Sea of Japan side, and then later a new group that came across from the continent, traveled along the Sanyodo (the region of Japan that stretches from Yamaguchi Prefecture to Hyogo Prefecture on the Seto Inland Sea side of Honshu) from Kyushu, and went on to build the Yamato imperial court.