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A joint research group led by Jonghyun Kim and Jun Ohashi of the University of Tokyo has demonstrated that the majority of immigration to the Japanese Archipelago in the Yayoi and Kofun periods (between 3000 BCE and 538 CE) came from the Korean Peninsula.

The researchers analyzed the complete genome of a "Yayoi" individual and found that, among the non-Japanese populations, the results bore the most similarity to Korean populations. Although it is widely accepted that modern Japanese populations have a dual ancestry, the discovery provides insight into the details of immigration patterns to the archipelago that have eluded scientists thus far.

The findings were published in the Journal of Human Genetics.

Today, Japan is an international hub for both business and pleasure. However, this was not always the case. The Japanese Archipelago was relatively isolated during the Jomon period until around 3000 BCE. Then, during the Yayoi and Kofun periods, immigration to the islands from continental Asia began.

"East Asian-related and Northeast Asian-related ancestries account for over 80% of nuclear genomes of the modern Japanese population," explains Ohashi, the principal investigator of the study. "However, how the Japanese population acquired these genetic ancestries—that is, the origins of the immigration—is not fully understood."

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