Satsumon culture, as it was known 500 years prior, disappeared, and in its place emerged the Ainu culture. The Ainu lived in square, above-ground houses (as opposed to pithouses), did not make ceramics, decorated their clothes with spiral motifs, and practiced agriculture on a small scale. They also participated in a ceremony during which a bear-cub was raised in captivity and sacrificed in order to send the bear-cub spirit back to the spirit world.
Trade continued to be important to the Ainu, but they found themselves competing with the samurai class of Japan and with Chinese military forces in the Amur River Valley. Trade can bring new goods and wealth, but it can also bring danger to a society. The Ainu built structures in the mountains around their villages, possibly fortified positions for protection from raids.
Geographic distance and barriers, such as the sea, separated Ainu communities in such a way that they begin to speak different dialects. Separate Ainu communities, resulting in cultural and linguistic differences emerged: Hokkaido Ainu, Sakhalin Ainu, and Kuril Ainu.
Political pressure from Russia in the 1800s and World War II forced Ainu populations out of Sakhalin Island and the Kuril Islands, leaving Hokkaido as the only place to go. Today, although many of their traditional lifeways have changed, there are between 20,000 and 60,000 Ainu living in Japan.
The project has apparently been taken off-line, however, you can still view the information through the Internet Archive here.