Ireibaru: The only settlement maintained for 4,000 years on a southern isle. Exchange conducted with Kyushu from the Early Jōmon.

Traces of livelihood using spring water
The site straddles a low marshy area at the base of a hill, and an area of sand dunes spreading over an alluvial plain. The sand dune area was residential, and the low marshy area evidently served as a kitchen using spring water, where a sieve for leaching tree nuts, pottery and stone tools were recovered. The photo shows the investigation of the low marshy area. A spring is on the right side of the photo.

Water gushes forth from the spring even today

Location of the site
It faces the East China Sea, on the southern half of the main island of Okinawa.

Sobata style pottery
This Early Jōmon pottery is strongly linked to Kyushu. It shows that exchange with that region was conducted from very early on. Height: 27.5 cm; rim diameter: 28.3 cm.

Murokawa lower strata style pottery
Early Jōmon pottery. Height: 34.8 cm; rim diameter: 30.0 cm.

Sieve set in the spring of the low marshy area Woven with local bamboo as the material, it is 1 m square. Placed where spring water flows, the four corners have stakes driven into them. As acorns of a white oak (Quercus miyagii Koidz.) were inside, it may have been used for storing nuts, etc.
Bracelet (Left half) Height: 9.7 cm; width: 3.5 cm. (Right half) Height: 9.7 cm; width: 3.4 cm.	Bone implements These are from the Middle to Final Jōmon. After catching and eating wild boar, porpoise, whale, dugong, etc., the bones were processed and accessories made from them. Included are items with relief carvings and other intricate designs. (Comb, in the center at the photo's back) Length: 8.0 cm; width: 4.2 cm.
First half, Early Jōmon (6,800 ∼ 6,000 BP) The Jōmon marine transgression was underway, and the sea level was high. People began to utilize the spring, and live in the vicinity. Tsumegatamon pottery of the southern islands region is found, along with stone tools. Rock shelters were apparently used for living quarters.	Second half, Early Jōmon (5,500 ∼ 5,000 BP) This appears to be the time during the Jōmon period when the spring was most utilized. Early Jōmon Sobata style pottery of Kyushu was found. Wooden implements were recovered, along with marine shells, animal and fish bone, seeds and nuts, and a sieve placed in a streambed thought to have been used for storing seeds. The coastline was close by the site. Dwellings were made on the western side of the hill, and on areas of continental sand.
Middle Jōmon (4,500 BP) A wooden vessel and board-shaped wood were recovered along with stone tools from the low marshy area, which appears to have been used as a kitchen at this time. Sand dunes formed at the edge of the hill on the southern side of the low marshy area, from where pit dwellings and the remains of a hearth have been found. The coastline at this time was receding.	Late Jōmon (3,500 BP) At this time the low marshy area was apparently not intensively utilized. Pit dwellings were distributed on the sand dunes, and saddle querns and other stone tools, Omonawa Tōdō style pottery which resembles that of the Amami region, and fish and animal bones were scattered around the residences. It was seen from the investigation that the sand dunes were eroded by high waves or storms, and the dwellings were receiving the effects (blue dotted line is the extent of the first period of erosion).
Final Jōmon (2,500 BP) A comb was found in a streambed in the low marshy ground, but the spring area does not appear to have been heavily utilized. New dunes formed in the sand dune area, and at the back of the dunes a stone-lined hearth was found. No dwellings have yet been found. Obsidian from Koshidake in Saga, and jade from the Hime river in Niigata have been found, revealing exchange over a wide geographic area.	A residence built in the sand dune area (from the eastern part of the site) During the Middle Jōmon, people began to live on sand dunes which formed on flat land. The size was 2 m square, and the floor paved with stones packed together.
Omonawa Zentei style pottery Middle Jōmon pottery. Rim diameter: 8.3 cm.	Omonawa Tōdō style pottery Late Jōmon pottery. Rim diameter: 20.5 cm.
Comb recovered from low marshy ground This came from a Final Jōmon feature in the low marshy ground. The color was bright at the time of discovery, but has blackened on exposure to the air. Made from ebony (genus Diospyros). Length: 8.0 cm; width: 4.2 cm.

Ireibaru Site, Chantan Town, Okinawa Prefecture

A settlement maintained at a low area near spring water

Ireibaru is a settlement site between 4 and 7 m elevation, on the western coast in the central portion of the main island of Okinawa, facing the East China Sea. People used the low marshy areas and sand dunes of the site as places of livelihood from the Jōmon period (ca 6,800 ∼ 2,500 BP) to the Gusuku period (fifteenth - eighteenth centuries).

The site was discovered in a test excavation in 1996, preceding a rezoning project in conjunction with the return of American military bases, and investigations were conducted from 1998 ∼ 2005 to verify its extent. The site spreads over a low area with spring water emerging at the base of a hilly slope, and it became clear that the lower marshy spots were used as a water source, and the sand dunes on the seaside as a place of residence. It was also ascertained that the older settlements were on the hilly slope to the east, spreading out towards the coast to the west in later eras.

Kyushu pottery is also recovered

From the lower marshy ground, along with Early Jōmon tsumegatamon pottery (ca 6,800 ∼ 6,000 BP), the oldest pottery for the southern islands region extending from the Amami archipelago up to Okinawa, the Sobata style of Jōmon pottery (ca 5,500 ∼ 5,000 BP) seen in Kyushu was also recovered, as well as pottery found from the Amami archipelago to the main and remote islands of the Okinawa chain for every period from the Middle to the Final Jōmon (ca 4,500 ∼ 2,500 BP). Also, stone tools such as axes, saddle querns and grindstones have been found along with the pottery, together with wooden implements including a stone axe handle, a comb and a sieve, and plentiful quantities of the remains of plants and animals that served as food, such as bones, marine shells, and the shells of nuts and seeds. The large amounts of Sobata style pottery recovered in this area was noteworthy. It can be divided into that which was brought directly from Kyushu, and that which was made in Okinawa. Exchange with Kyushu from a very early stage of the Jōmon can be seen from this, and movement to the south of people using Sobata style pottery is conceivable. Subsequently, it is thought that the Jōmon culture brought with them took root, and gradually formed the unique Jōmon culture of the southern island region.

From the sand dune area, pit dwellings of the Middle and Late Jōmon were found, along with stone formations, pits, and a Final Jōmon hearth. For the pit dwellings, 1 example (with a round plan) for the Middle, and 2 examples (square in plan with rounded corners, and stone-paved floors) for the Final Jōmon have been confirmed. In addition, 7 stone formations have been ascertained, and from the size and shape it s possible these were dwellings. The pit dwellings and stone formations are found to have spread out along a north-south direction.

Why did settlement last 4,000 years?

A wide variety of artifacts are seen for every period from the Early to the Final Jōmon, such as pottery, stone axes and mortars, and bone and shell implements. Obsidian originating from Koshidake in Saga prefecture, and jade from the Hime river in Niigata prefecture, were found here for the Final Jōmon period. These may be said precious materials for considering exchange which took place across a broad area, extending to Kyushu and Honshu.

Ireibaru was a site that lasted 4,000 years, a phenomenon seen only here and without parallel in the southern islands. It is thought that settlement continued for such a long time in this area only because provisions for livelihood could be readily obtained from the bounties of the mountains and the sea. (Tōmon Kenji)