Where did Japanese people come from? The University of Tokyo and Toho University find that immigrants from the Korean Peninsula mixed with Jomon people — Birth of the ancestor of the Japanese

There are various theories regarding the origin of the Japanese, but a research group led by Doctoral Student Jonghyun Kim and Professor Jun Ohashi of the Graduate School of Science at the University of Tokyo, in collaboration with Lecturer Fuzuki Mizuno at Toho University School of Medicine and Director Takayuki Matsushita of the Doigahama Site Anthropological Museum analyzed the whole genome sequence of a Yayoi individual found at the Doigahama Site in Yamaguchi prefecture and identified the roots of the immigrants to the Japanese archipelago from eastern Eurasia in the Yayoi period. The results showed that a population with both genomic components characteristic of East Asian and Northeast Asian populations migrated from the Korean Peninsula to the Japanese archipelago during the Yayoi period and formed the ancestral population of the modern Japanese after admixture with the Jomon people.

Various theories explain the formation process of the Mainland Japanese (excluding the Ainu and Okinawan populations), but the dual-structure model proposed by Kazuro Hanihara is widely accepted. This model suggests that "the modern Japanese are descendants of the admixed population between the Jomon people, who are descendants of populations that inhabited the Japanese archipelago during the Upper Paleolithic period, and the immigrants of Northeast Asian origin, who came to the Japanese archipelago between the Yayoi and Kofun periods." Although this model was proposed based on analysis of skull morphology, previous genetic studies have supported the idea that the Japanese are descendants of the admixed population between Jomon people and immigrants.

The nuclear genome components of the modern Japanese are divided into three major categories: components derived from the Jomon people (Jomon components), components characteristic of East Asian populations (East Asian components), and components characteristic of Northeast Asian populations (Northeast Asian components). Although the East Asian and Northeast Asian components account for more than 80%, how the Japanese acquired these components was not fully understood, i.e., the roots of immigrants.

The research group extracted DNA from the skeletal remains of a Yayoi individual excavated from the Doigahama site and successfully obtained sufficient data through whole-genome sequencing. To explore the roots of the immigrants, they conducted statistical analyses using genome data from the Doigahama Yayoi individual, Jomon people, Kofun people, and modern Japanese, as well as East Asian and Northeast Asian populations. They found that the Doigahama Yayoi individual had the aforementioned three types of genomic components of modern Japanese and was genetically closest to the Kofun people among the analyzed populations, followed by modern Japanese, ancient Korean individuals, and modern Korean individuals.

Next, they statistically evaluated a model assuming that modern Korean individuals with both East Asian and Northeast Asian genomic components migrated to the Japanese archipelago and the population (individuals) of interest was originated from the admixed population between the immigrants and Jomon people. The result showed that this simple model could well explain the genomic components of the Doigahama Yayoi individual, the Kofun people population, and the modern Japanese population.

These findings strongly suggest that a population with both East Asian and Northeast Asian genomic components migrated from the Korean Peninsula to the Japanese archipelago during the Yayoi period and admixed with the Jomon people to form the ancestors of the modern Japanese people. The clarification of the major roots of the immigrants in this study is expected to contribute to deeper understanding of the formation process of the Japanese population.

Journal Information
Publication: Journal of Human Genetics
Title: Genetic analysis of a Yayoi individual from the Doigahama site provides insights into the origins of immigrants to the Japanese Archipelago
DOI: 10.1038/s10038-024-01295-w