During the first half of the Middle Jomon period (ca 5400-4900 years ago), the people at Sannai Maruyama still mainly lived in pit dwellings. However, new complexity to the site began, with specific burials, storage facilities, and a few six pillared buildings.
Six-pillared buildings are something the archaeologists have surmised from the data. In several places, six postmolds are set in a rectangular pattern. Postmolds are circular stains in the earth, signs where wooden posts were purposefully placed in the earth and eventually rotted there. The six-pillared buildings don't have built floors--at least none at ground level, and there are many fewer of them than pit dwellings. Archaeologists have interpreted these as raised floor dwellings or special storage facilities.
Sources
See the Jomon Timeline and Definition for more specifics on the culture.
See the official Sannai Maruyama website for further information. If you are planning a visit to Japan, the site is open to visitors, with a museum and several reconstructed buildings.
Habu, Junko 2008 Growth and decline in complex hunter-gatherer societies: a case study from the Jomon period Sannai Maruyama site, Japan. Antiquity 82:571–584.
Habu, Junko and Clare Fawcett 1999 Jomon archaelogy and the representation of Japanese origins. Antiquity 73:587-793.
Habu, Junko, Minkoo Kim, Mio Katayama, and Hajime Komiya 2001 Jomon subsistence-settlement systems at the Sannai Maruyama site. Bulletin of the Indo-Pacific Prehistory Association 21:9-21. Free download
Anonymous. The Sannai Maruyama Site: Extraordinarily Large Settlement in Prehistoric Japan. Undated pamphlet available at the Sannai Maruyama site webpage.
