Japan has long held a particular position as a place of interest for archaeological studies for quite some time now. It has long been thought that the Japanese can trace their origins from two distinct genetic groups that inhabited the islands thousands of years ago, sometimes named the “dual ancestry” model.
In this dual-ancestry model, the Japanese derive their ancestry from the indigenous peoples of the ancient Jomon hunter-gatherer-fisher culture, inhabitants of the Japanese islands from around 16,000 to 3,000 years ago. This was then followed by a second wave of migrations to the archipelago from around 900 B.C. to 300 A.D., by the peoples of the Yayoi farmer culture. This very model, however, may be set for a rewrite. Researchers led by assistant professor for psychiatry at the Trinity College Dublin’s School of Medicine Shigeki Nakagome may have found a third source to the current established model of Japanese ancestry: ancient peoples linked to the Kofun culture that arrived to the archipelago between 300 to 700 A.D.. The landmark study was published in the journal Science Advances.
Here, Nakagome and an international team of researchers from both Japan and Ireland studied and sequenced 12 ancient Japanese genomes, which led them to their startling discovery. The newly-sequenced genomes were obtained from individuals who lived in both pre- and post-farming periods of ancient Japanese history, which had been established as a significant event during the time of the Yayoi people. It appears that later on, at around 300 A.D., an influx of East Asian ancestry was introduced to the genetic pool during the imperial Kofun period, which coincided with the beginnings of Japan’s political centralization.
Alongside these findings, studies into population size estimates of the Jomon people revealed them to hover around 1,000 over several thousand years, with a divergence event in Japanese genetic history appearing about 20,000 to 15,000 years ago. This event, evidenced by their genetic heritage drifting away from those living in mainland Asia, was said to be associated with the rise in sea levels following the end of the last Ice Age. At the time, a land bridge connected Japan to what is now the Korean peninsula; people and cultures traversed through these lands, which the authors say also correspond to the dates of Jomon artifacts obtained from around this time, which included poetry.
Niall Cooke, PhD researcher from Trinity College Dublin, added that “the indigenous Jomon people had their own unique lifestyle and culture within Japan for thousands of years prior to the adoption of rice farming during the subsequent Yayoi period,” and that “these results strongly suggest a prolonged period of isolation from the rest of the [Asian] continent.”
Said Nakagome: “Researchers have been learning more and more about the cultures of the Jomon, Yayoi, and Kofun periods as more and more ancient artefacts show up […].” He added: “We now know that the ancestors derived from each of the foraging [Jomon], agrarian [Yayoi], and state-formation [Kofun] phases made a significant contribution to the formation of Japanese populations today. In short, we have an entirely new tripartite model of Japanese genomic origins — instead of the dual-ancestry model that has been held for a significant time.”
The transition between the pre-farming Jomon and farming Yayoi period was quite different from similar cultural transitions that happened in Europe, according to the research team. Instead of population replacement, wherein a takeover of one people group removes most of the presence of another, the ancient Japanese seem to have assimilated these future groups instead. This, said the team, led to the “almost equal genetic contributions” among the Jomon and Yayoi people in the current Japanese genome.
Study co-leader Dan Bradley, from the Trinity College Dublin’s School of Genetics and Microbiology, finished by saying that “the Japanese archipelago is an especially interesting part of the world to investigate” due to its “exceptional prehistory of long-standing continuity followed by rapid cultural transformations.” “Our insights into the complex origins of modern-day Japanese once again shows the power of ancient genomics to uncover new information about human prehistory that could not be seen otherwise.”
(To read more on how ancient history can be viewed through the lens of genetics, here is our piece of how genetic analysis of Southeast Asian peoples revealed parts of their true past.)
References
- Cooke, N. P., Mattiangeli, V., Cassidy, L. M., Okazaki, K., Stokes, C. A., Onbe, S., Hatakeyama, S., Machida, K., Kasai, K., Tomioka, N., Matsumoto, A., Ito, M., Kojima, Y., Bradley, D. G., Gakuhari, T., & Nakagome, S. (n.d.). Ancient genomics reveals tripartite origins of Japanese populations. Science Advances, 7(38), eabh2419. https://doi.org/10.1126/sciadv.abh2419
- Dunham, W. (2021, September 17). Study rewrites understanding of modern Japan’s genetic ancestry. Reuters. https://www.reuters.com/world/asia-pacific/study-rewrites-understanding-modern-japans-genetic-ancestry-2021-09-17/
- Trinity College Dublin. (2021, September 17). Ancient DNA rewrites early Japanese history—Modern day populations have tripartite genetic origin. ScienceDaily. https://www.sciencedaily.com/releases/2021/09/210917161149.htm
