A research group led by Professor Yasuo Ihara of the University of Tokyo, in collaboration with the National Museum of Nature and Science and the National Museum of Nature and Science, analyzed the advancement of humans into the island by accidental drifting, and it is said that a group of about 10 people crossed the island. For example, it was shown that the descendants may have persisted as a group.
Late Pleistocene humans crossed the sea and advanced to islands like the Ryukyu Islands in Japan.If it was a deliberate migration, it would be a good nautical technique at the time, but if it was a coincidence, it has been debated for many years how many drifters were needed to maintain the population of its descendants.
This time, we evaluated the possibility that the descendants of migrants will continue as a group by population simulation.Since modern-day hunter-gatherers travel on a family-by-family basis, the accidental drift of a boat on which the family was aboard was compared to the deliberate migration by the same number of young men and women.A comprehensive study of realistic combinations of fertility and mortality as hunter-gatherers shows that in the case of accidental drifting, the sustainability of the population is significantly less than that of intentional migration, and the sustainability of the population is significantly less than 10 under many conditions. It turned out that about a few drifters were needed.
For example, in the Ryukyu Islands, Homo sapiens appeared in the entire archipelago 3 to 5000 years ago, but the islands were small and separated, and there were complex and strong currents including the Kuroshio Current.Therefore, it is difficult for sustainable numbers to drift ashore, and from this result, it seems that the advance of humankind to the Ryukyu Islands is a deliberate migration.On the other hand, in Indonesia around 3 million years ago, the original people crossed the narrow strait several times to Flores Island.The islands in this area are large, and it seems possible for about 100 men and women who were accidentally washed away by the tsunami to be washed ashore at the same time.
Instructor Ihara said that there was some strong motivation to go out to the sea knowing the danger, and pointed out that it may have been the driving force for the spread of humankind to the world.
Paper information:[Journal of Human Evolution] A demographic test of accidental versus intentional island colonization by Pleistocene humans
