(Door) Are our ancestors the 20,000-year-old Minatogawa people? DNA analysis suggests a possible link to the Japanese people

The Minatogawa people—a keyword—whose nearly 20,000-year-old full skeletons were discovered in Okinawa Prefecture, may have been ancestors linked to modern Japanese people. This possibility has been revealed through DNA analysis. While the established theory for the roots of the Japanese people is the "admixture hypothesis" involving indigenous Jomon people and migrants from the continent, the possibility of tracing them back even further has emerged.

DNA analysis and other studies have confirmed that the origins of the Japanese people trace back to the Yayoi people, who were a mixture of the Jomon people, who were widely distributed from Hokkaido to Okinawa between approximately 15,000 and 3,000 years ago, and the migrants who arrived from the continent thereafter.

On the other hand, the relationship with the Minatogawa people, who existed from a time earlier than the Jomon people, had not been clear. This is because human bones and ruins alone leave open the possibility that the Minatogawa people moved to other lands or died out, meaning they are not necessarily direct ancestors. The fact that the skeletal structure of the Minatogawa people's faces does not closely resemble that of the Jomon people has also been a subject of debate.

A research team including members from the Graduate University for Advanced Studies (SOKENDAI) and Toho University adopted a method using mitochondrial DNA, an organelle in cells that is relatively easy to analyze. They successfully extracted and analyzed DNA for the first time from the right femur of Minatogawa Man No. 1, whose remains were well-preserved and included a full skeleton.

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Mitochondrial DNA has the characteristic of being passed from mother to child, and due to mutations that occur during this process, slight differences rarely arise even between parent and child. By comparing these traces left in the DNA, one can trace the lineage of that individual or group.

The results of the analysis revealed that Minatogawa Man No. 1 possessed the ancestral characteristics of a type of gene commonly found in modern Japanese, Jomon, and Yayoi people. This suggests the possibility that the lineage of the Minatogawa people's descendants has continued to the present day without interruption.

However, among the approximately 2,000 modern Japanese people analyzed, there were no direct descendants who inherited the same genetic characteristics as Minatogawa Man No. 1.

Jun Gojobori, a lecturer at SOKENDAI (physical anthropology) who is part of the team, says, "It seems likely that human groups on the Japanese archipelago have been genetically connected from the Paleolithic era to the present day." He added that as research progresses, it is possible that direct descendants of the Minatogawa people could be found among modern Japanese people.

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Minatogawa Man No. 1 was 153 centimeters tall, which was small for an adult male. Analysis of the skull shows that the temple muscles were developed and the lower jawbone was sturdy. The teeth were also strong, with particularly thick and long roots supporting the molars. From another nearby cave, the world's oldest fishhooks made from spiral shells 23,000 years ago, as well as crab claws and eel bones, have been found.

Hisao Baba, an honorary researcher at the National Museum of Nature and Science (human morphology), observes, "They ate mice and fish bones and all, and crunched through hard things like tree roots. Their cooking was likely limited to just roasting over a fire."

What can be understood from the skull is that its features, such as the rugged head shape and deep-set eyes with prominent brow ridges, retain the ancient appearance of Homo sapiens (early modern humans) who emerged in Africa about 200,000 years ago. It is said to closely resemble the indigenous people of Australia and the Wajak people, who were discovered in Indonesia and possess primitive features in their skulls.

Baba speculates, "Perhaps early modern humans who came to East Asia from Africa about 40,000 years ago crossed over to Okinawa and became isolated, adapting to the environment while retaining their ancient features to become the Minatogawa people."

Gojobori and his research team plan to begin analysis of nuclear DNA, which contains more information than mitochondrial DNA, using Minatogawa Man No. 1. If successful, they say they will be able to understand the relationship between the roots of the Japanese people and the Minatogawa people more clearly. (Tetsuya Ishikura)

◆ Keyword

<Minatogawa People> In 1970, the full skeletons of four men and women from the Paleolithic era, dating back about 20,000 years, were found in a rock crevice called a "fissure" in Yaese Town, Okinawa Prefecture. They are called the Minatogawa people after the place name where they were excavated. In contrast to their small and slender upper bodies, they had sturdy skeletal legs, hips, and jaws. It is believed they lived a hunter-gatherer lifestyle while wandering in groups across the island, which had little flat land and was rugged. It is extremely rare for full skeletons from the Paleolithic era to be found in Japan.

The discoverer, the late Seisho Oyama, a businessman from Naha, found wild boar bones at the site three years before discovering the human bones. Since then, he had reportedly continued the excavation, believing that "there must be human bones that I have been chasing."