Unraveling the Tripartite Origin: A New Perspective on Japanese Ancestry

Researchers from RIKEN and other institutions have conducted a comprehensive analysis of Japanese whole-genome sequencing data, challenging the prevailing "binary structure model" of Japanese ancestry. Instead, they present evidence supporting the "tripartite origin model," which suggests that Japanese ancestors can be traced back to three distinct branches.

The RIKEN Institute of Japan recently issued a press release announcing that the commonly accepted model of Japanese origin is the "dual structure model." This model posits that the modern Japanese population evolved from a mixture of indigenous Jomon people, who inhabited the Japanese archipelago during the Neolithic Jomon Period, and rice-farming immigrants who migrated from the Asian continent during the Yayoi Period, spanning from the mid-3rd century BC to the mid-3rd century AD.

In recent years, some researchers studying human remains unearthed across Japan have proposed an alternative theory known as the "tripartite origin model." According to this model, the Japanese population is the result of a blending of three distinct groups: the Jomon people, a group originating in Northeast Asia that migrated to Japan during the Yayoi period, and a group originating in East Asia that arrived in Japan during the Kofun period (primarily from the mid-3rd century to the end of the 7th century AD). However, due to the scarcity of ancient human bone genome samples, further evidence was needed to support the "tripartite origin model."

The recent research conducted by RIKEN and the University of Tokyo is based on an extensive dataset of modern Japanese genomes and provides new evidence in favor of the "tripartite origin model." The study involved analyzing whole-genome sequencing data from over 3,250 individuals across seven regions in Japan. The findings indicate that the genetic makeup of the Japanese population is a combination of three ancestral lineages: the Jomon line and its affiliated lineage, the Western Japanese lineage, and the Northeastern Japanese lineage. To further investigate genetic affinities, the research team also examined ancient human genome data from China, South Korea, and Japan. Their analysis revealed a significant genetic similarity between individuals from the Kansai region and ancient Chinese populations residing in the Yellow River and its upper reaches during the middle and late Neolithic Age. Conversely, individuals from the Northeastern region of Japan exhibited a notably higher genetic affinity with the Jomon people.

This study contributes to our understanding of the complex origins of the Japanese population and emphasizes the importance of considering multiple ancestral influences. By leveraging large-scale genomic data, the research teams have shed new light on the evolutionary history of Japan and challenged the prevailing binary structure model in favor of the tripartite origin model.