The long-term use of freshwater animals by Paleolithic people on subtropical Okinawa Island, Japan

Migration to islands requires developing subsistence strategies with limited resources. Okinawa Island, a remote subtropical island in Japan, was colonized by Homo sapiens at the end of the Pleistocene. Recent excavations at the Sakitari Cave site have revealed that Pleistocene people used freshwater crabs and snails as food resources between 35,000 and 13,000 years ago. Because long-term use of specific resources can affect animal populations, this study examined temporal changes in the proportions of animal taxa and size variation in freshwater crabs and snails obtained from Sakitari Cave. The results showed that terrestrial mammals were limited in their food consumption, and the proportion of freshwater resources increased during the Last Glacial Maximum and/or after deer extinction. And no size-reduction was observed in freshwater crabs and snails. These small-sized aquatic animals have high reproductive capacity and population density, and thus can be utilized for a long period of time on the island.