Some five thousand archaeological sites to date provide an understanding of Japan in the Paleolithic (Stone Age), or Pre-Ceramic era. Despite considerable debate about the length and nature of the prehistoric chronology, a number of facts emerge. Originally Japan was linked to the Asian continent by land bridges to Siberia and Korea. Over these arrived the earliest peoples in successive waves of migration. Genetic and linguistic studies indicate that these ancestors, bearing Archaic Mongoloid traits, arrived from around Lake Baikal in Russian Central Asia, and later from Southeast Asia and China by way of Korea. Most major original migrations take place by the end of the Paleolithic era; and as these peoples intermix and adapt to environmental changes, they evolve to form the modern Japanese. Today only the aboriginal peoples of the north, the Ainu of Hokkaido, and of the extreme south, the Ryukyuans of Okinawa, remain ethnically distinct, bearing close connections to the peoples of prehistoric times. These Paleolithic peoples are hunters, fishermen, and gatherers of plant foods. Inhabiting seasonal temporary settlements, they live as self-sufficient, multigenerational family groups known as bands (made up of from 20 to 150 members). They leave behind fragmentary architectural remains; increasingly complex stone tools; sporadic burials, some with grave goods; and evidence of trading networks.
200,000?B.C.: Sea recedes from the Kanto Plain around Tokyo, leaving the marine deposit known as the Shimosueyoshi Formation. From c. 130,000 to 13,000 B.C., several volcanic eruptions deposit distinct layers of ash atop the formation. This stratigraphic geological sequence will serve to date Paleolithic archaeological sites there and elsewhere in Japan, with much scholarly debate about chronology.
Crude stone tool assemblages, but no human fossil evidence, found at sites in Oita, Tochigi, and Miyagi prefectures are posited by excavators to be some 200,000 years old and to suggest the earliest immigration of Homo erectus to Japan.