The background of transitions in microblade industries in Hokkaido, northern Japan

The purpose of this paper is to discuss the archaeological transitions among microblade industries in Hokkaido and to propose some possible relations between human activities and natural environment. Hokkaido is situated in the north of the Japanese archipelago, and the microblade industries in this region lasted approximately from 24,000 to 13,000 cal BP, corresponding to the climatic changes of the MIS2 Last Glacial Maximum (LGM) Cold2 and MIS2 Late Glacial Warm (LG Warm). The primary purpose of this paper is to describe the whole picture of transitions observed in microblade industries through a series of examinations on the size of microblades, maintenance of burins, and the stone tool classes. Results suggest that the following changes in hunting-related stone tools were occurred during the LG Warm: 1) miniaturization in the part of spears (microblades), 2) high frequency in burin maintenance, and 3) appearance of the new hunting weapon (i.e., projectile points), and axes. Then, a preliminary discussion on the possible relations between human activities and the natural environment including some significant climate changes is made referring to the recent studies on the analyses of charred deposits on pottery from the Taisho 3 site which belongs to LG Warm. Given the fact that the alterations in the environment and human activities were coincident, I propose the hypothesis that the transitions in microblade industries in Hokkaido was an outcome of human adaptation to the fluctuation in accessible natural resources caused by the globally occurred warming trend.