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Human migrations to the Ryukyu Islands were led by explorers, not drifters

Researchers at the University of Tokyo have determined that a human migration from Taiwan to the Ryukyu Islands 35,000 years ago was an intentional move, and did not happen just by chance. The team used satellite-tracked buoys to simulate ancient humans drifting at sea. The vast majority of the buoys did not successfully complete the crossing

Tracking human migrations over the last 50,000 is key to understanding human history. There has been a lot of debate as to the degree of intentionality behind the movement of Paleolithic people from Taiwan to the Ryukyu Islands, including Okinawa, between 35,000 and 30,000 years ago. 

“There have been many studies on Paleolithic migrations to Australia and its neighboring landmasses, often discussing whether these journeys were accidental or intentional,” said Professor Yosuke Kaifu. “Our study looks specifically at the migration to the Ryukyu Islands, because it is not just historically significant, but is also very difficult to get there. The destination can be seen from the top of a coastal mountain in Taiwan, but not from the coast. In addition, it is on the opposite side of the Kuroshio, one of the strongest currents in the world. If they crossed this sea deliberately, it must have been a bold act of exploration.”

To investigate the likelihood of arriving at the Ryukyu Islands by chance, the researchers deployed 138 satellite-tracked buoys to mimic drifters making the ocean journey out of Taiwan.

“The results were clearer than I would have expected,” said Professor Kaifu. “Only four of the buoys came within 20 kilometers of any of the Ryukyu Islands, and all of these were due to adverse weather conditions. If you were an ancient mariner, it’s very unlikely you would have set out on any kind of journey with such a storm on the horizon. What this tells us is that the Kuroshio directs drifters away from, rather than towards, the Ryukyu Islands; in other words, that region must have been actively navigated.”

According to geological records as well as other existing evidence, the currents in this region have been stable for at least the last 100,000 years. Previous studies also suggest that Paleolithic voyagers would not have risked heading out into stormy conditions, which eliminates the possibility that ancient humans stumbled upon the Ryukyu Islands by chance. 

“At the beginning, I had no idea how to demonstrate the intentionality of the sea crossings, but I was lucky enough to meet my co-authors in Taiwan, leading authorities of the Kuroshio, and came across the idea of using the tracking buoys,” said Professor Kaifu. “Now, our results suggest the drift hypothesis for Paleolithic migration in this region is almost impossible. I believe we succeeded in making a strong argument that the ancient populations in question were not passengers of chance, but explorers.”

The study is published in the journal Scientific Reports.

By Chrissy Sexton, Staff Writer

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