Examining frequency and directionality of Palaeolithic sea-crossing over the Korea/Tsushima Strait: a synthesis

Offshore landmasses in the Western Pacific were colonized during the Late Pleistocene through deliberate seafaring by modern humans. However, our knowledge of the developmental process of the Palaeolithic seafaring is still limited due to lack of reliable chronology for such seafaring. To contribute to this issue, we synthesize lines of evidence on repeated sea-crossings over the Korea/Tsushima Strait, a major passage to the Japanese archipelago. Shortly after the earliest evidence of flake assemblages around 39,000–37,000 cal BP, a sudden appearance of blade reduction is observed, suggesting multiple sea-crossings over this strait in the early Upper Palaeolithic. Subsequently, a unique type of stemmed points spread across the strait, signaling another sea-crossing during 29,300–27,500 cal BP. Furthermore, the obsidian provenance analysis suggests bidirectional sea-crossings during the Last Glacial Maximum. These sea-crossings seem to have occurred regardless of narrowness of the strait with changing sea level, whereas it is possible that bidirectional crossing was triggered by this factor.