The degree of intentionality behind ancient ocean migrations, such as that to the Ryukyu Islands between Taiwan and mainland Japan, has been widely debated. Researchers used satellite-tracked buoys to simulate ancient wayward drifters and found that the vast majority failed to make the contested crossing. They concluded that Paleolithic people 35,000-30,000 years ago must therefore have made the journey not by chance but by choice.1

  • 1. "There have been many studies on Paleolithic migrations to Australia and its neighboring landmasses, often discussing whether these journeys were accidental or intentional," said 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."

Yousuke Kaifu, Tien-Hsia Kuo, Yoshimi Kubota, Sen Jan. Palaeolithic voyage for invisible islands beyond the horizon. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-76831-7

How Palaeolithic maritime transportation originated and developed is one of the key questions to understand the world-wide dispersal of modern humans that began 70,000–50,000 years ago. However, although the earliest evidence of maritime migration to Sahul (Australia and New Guinea) has been intensively studied, succeeding development of Paleolithic maritime activity is poorly understood. Here, we show evidence of deliberate crossing of challenging ocean that occurred 35,000–30,000 years ago in another region of the western Pacific, the Ryukyu Islands of southwestern Japan. Our analysis of satellite-tracked buoys drifting in the actual ocean demonstrated that accidental drift does not explain maritime migration to this 1200 km-long chain of islands, where the local ocean flows have kept the same since the late Pleistocene. Migration to the Ryukyus is difficult because it requires navigation across one of the world’s strongest current, the Kuroshio, toward an island that lay invisible beyond the horizon. This suggests that the Palaeolithic island colonization occurred in a wide area of the western Pacific was a result of human’s active and continued exploration, backed up by technological advancement.

Figure 2: Trajectories of the 137 SVP drifters departed from off the east coasts of Taiwan and northern Luzon, and the years and the seasons of the track records
Figure 2: Trajectories of the 137 SVP drifters departed from off the east coasts of Taiwan and northern Luzon, and the years and the seasons of the track records - White circles and black squares are the start and end points of the drifters, respectively. Six trajectories that traversed the Kuroshio are colored. The areas within 20 km from the coasts of the islands of Central and South Ryukyus are circled.