Since the first Palaeolithic site (Iwajuku in Honshu) was excavated in Japan twenty one years ago, some five hundred sites between the ages of 30000 and 10000 years BP have been inevestigated. Vertical stratifications of assemblages are present at some twenty of the sites, and thirteen radiocarbon determinations have now been obtained. On the basis of these materials, which are of course by no means sufficient, it is possible to suggest a general outline for the chronological sequence of the Late Palaeolithic cultures in Japan.
In this paper, the writer wishes to discuss problems of the human occupation of Japan prior to 30000 BP. A radiocarbon determination in excess of 31900 BP has been obtained for Cultural Horizon 7 of Fukui Cave, and lithic artifacts are being recovered from the Musashino and Shimosueyoshi loam deposits which predate 30000 BP. As an example, Fig. 4 shows some columnar sections at the famous Iwajuku site in Honshu. Two assemblages named Iwajuku I and Iwajuku II were obtained from Locality A during excavation in 1949. The dark zone in which Iwajuku I occured is dated to 24000 BP. Recent re-investigation of the site have revealed the existence of another artifact-bearing horizon at Locality D: the artifacts are made in quarzite and the horizon is clearly below the Hassaki pumice layer. These artifacts, therefore, should predate to be 30000 BP (Fig. 5).
These older assemblages include choppers, chopping-tools, pointed tools, proto-handaxes, flakes, cores, and hammer-stones. The ratio of flake tools to core tools is approximately 5:5 or 4:6. Frequently the implements are made on chert, quartz vein or quarzite. It is possible that Lower Palaeolithic peoples of mainland Asia reached Japan during the time of the last major sea transgression, and that, they or their descendants left the assemblages which we are now recovering. As to the feasibility of the entry, some geologists are now suggesting that the area of the Korean Strait was probably dry at the time of the transgression; therefore, human and faunal movements from the Asiatic mainland were not entirely impossible.
