The radiocarbon dates so far obtained from the Jomon and Yayoi periods in Honshu and the relevant periods in Hokkaido were plotted on a graph according to the chronological order of pottery types in archaeological framework. The distribution of plotted points is in general consistent with the chronological sequence of pottery types except for the earliest Jomon period. As to this period, plotted points of Hokkaido are markedly dispersed within a wide range of time and those of Honshu are inconsistent with the chronological order of pottery types. Moreover, in the latter there is a gap of 2500 years which is too long as to be assigned to the period of eight pottery types having no available radiocarbon date as yet. In this respect, the discrepancy between the radiocarbon date and the true age which is possibly due to the climatic change in the past seems to provide an adequate interpretation.
