The West may know more about Japan than any other Asian nation. This is understandable given the fascination with a culture so unknown and different in many ways. While I could list countless elements of its history and culture, the most important thing is what has been missing: the origin of its modern population. However, a new study has just provided the answer.
The news. After years of debate and contradictory studies, research published in August appeared to offer a definitive answer. It suggested that the genes of the modern Japanese may contain traces of long-lost ancestors who once migrated from northeastern mainland Asia to the archipelago.
However, a newly published study from the University of Tokyo has revealed significant new evidence about the origins of the Japanese population. It challenges previous theories and provides a more nuanced understanding of the process of genetic formation. The key is an analysis of ancient DNA that refines the ancestry model of the Japanese population, according to an English translation provided by Google.
Earlier models. The earliest study on the origins of the Japanese dates back to the 1950s, when researchers proposed a dual ancestry model. They suggested that two main groups made up the population: the Jōmon people, indigenous hunter-gatherers, and the Yayoi people, immigrants from the Asian continent, primarily from the Korean peninsula. But a 2021 study changed everything, proposing a tripartite ancestry model by adding a previously unknown group from Northeast Asia.
Another paper this year supported this theory. It analyzed the DNA of 3,200 Japanese people from various regions and confirmed an admixture between the Jōmon, the Yayoi, and a Northeast Asian group. However, this theory lacked a crucial element: an explanation of how this admixture occurred and how it influenced agriculture and language practices.
The new study. Conducted by the University of Tokyo, the new research provides the most precise and accurate evidence to date using ancient DNA analysis. Researchers sequenced the DNA of a 2,300-year-old Yayoi-era woman whose remains were discovered in 1952 at the Doigahama ruins in Yamaguchi Prefecture.
Apparently, an area containing the remains of 300 people from the Yayoi period was key to the development of the dual ancestry model because of the differences observed between the Yayoi and Jōmon remains.
The genetics of the Japanese. Genetic analysis has confirmed the presence of three ancestral groups in the modern Japanese: the Jōmon, the Yayoi, and the Northeast Asian group. However, the study made an important adjustment to the previous model, concluding that the Northeast Asian group didn’t arrive in Japan independently. Instead, they had already mixed with the Yayoi people before migrating to the Japanese archipelago. This finding partially contradicts the 2021 model, which suggested that the three populations arrived separately.
Genetic model. To reach this conclusion, researchers used a genetic model to analyze how modern Koreans, who have both East Asian and Northeast Asian genetic components, would have mixed with the Jōmon people in Japan. Using this model, they found striking similarities with the DNA of modern Japanese, supporting the hypothesis that the Yayoi people had already had contact with the Northeast Asian group before arriving in Japan.
Indeed, Koreans were the key “neighbors” in modern Japanese society.
Implications. This study is also crucial in understanding how intermingling migrations and indigenous peoples shaped the Japanese population. The researchers conclude that, although modern Japanese have tripartite origins, these groups didn’t migrate independently but had previously intermingled on the Asian continent.
This genetic admixture reflects a much more complex process than previously thought. As a result, experts plan to study more genomes of Yayoi-era individuals to better understand how this combination occurred.
Finally, the findings reinforce the idea that more than 80% of the genetic components of the modern Japanese population come from immigration, not just the indigenous Jōmon people. By shedding light on how mainland Asian and Jōmon populations interacted, the study marks a milestone in understanding Japan’s genetic evolution.
Image | graffiti living | University of Tokyo
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