Hijiridaki is a limestone cave about 50 m long and 200 m above sea level, in Honjo Village, Oita Prefecture. It is thought to be a Medieval burial place. Archaeologists and anthropologists learned of this cave and became interested in some skeletons with travertine adhesions that were found there. KAGAWA Mitsuo and OGATA Tamotsu directed excavations at the cave in 1961 (preliminary) and 1962 (full scale), the latter being one of the special research projects in cave sites, conducted by the Japanese Archaeological Association in the early 1960s. Finds included human skull fragments, a human talus, microblades, a microcore, a trapeze, and so on. All of the artifacts were obsidian and were regarded as belonging to the final phase of Late Palaeolithic. The human remains and artifacts were obtained from the same layer, and thus were considered to be contemporary. Palaeolithic human skeletons were unusual in the Japanese islands.
HARUNARI Hideji, the head of the Archaeology Section of the research project "The Interdisciplinary Study on the Origins of the Japanese People and Culture" (Grant-in-Aid for Scientific Research on Priority Areas; Project Number 09208103; OMOTO Kei'ichi as the head of project), recently attempted to reexamine the site and to elucidate its nature. The new excavation team was organized as follows:
|Vice-Directors||HARUNARI Hideji, ODA Shizuo|
|Advisers||KAGAWA Mitsuo, OGATA Takahiko|
|Archaeological staff||TSUJIMOTO Takeo, and others|
|Anthropological staff||NARASAKI Shuichiro, and others|
|Paleozoological staff||KAWAMURA Yoshinari, and others|
|Dating staff||MATSU'URA Hideji, KONDO Megumi|
|Surveyor||Maizo-Bunkazai Support System Co.|
The field work was carried out from the 10th through the 22nd of December, 1999, with the great cooperation of Honjo village. Many scholars and students from north to south, from Miyagi to Okinawa, volunteered to join the excavation.
Deposits in the cave contained three layers. The humus layer I was 10 to 15 cm thick, the sandy gravel layer II was 15 to 25 cm thick, and the bottom clayish layer III was deeper than 3 m. Layer I included Medieval human skeletons and coins, layer II lacked artifacts, and the topmost part of layer III included a few human and animal remains. The cave is a fissure or fault, which may have formed in the early part of the Pleistocene. The animal remains from the topmost part of layer III were bats, rats, and moles. All of them are present types of species, that is to say, Holocene. According to the radiocarbon dating of charcoal, the topmost part of layer III formed about the fifteenth to seventeenth century; human bone from a disturbed deposit was dated around the fourteenth to fifteenth century. The Medieval context is evident, but there was no primary Pleistocene context inferable in the deposits in any part of the cave.
The 14 or 15 obsidian artifacts and the human remains unearthed in 1961 were controversial from the first report. The issue was conceived by KAGAWA Mitsuo, GOTOH Shigemi and OGATA Tamotsu, and they regarded reexamination as necessary. But they did not reexamine the site and repeatedly published affirmative comments in papers. In 1981, TACHIBANA Masanobu published a report on 26 obsidian implements as artifacts unearthed from the cave, but he did not notice a jumble of artifacts from other sites. Nobody paid attention to the true number of artifacts. Further, there is no site yielding only obsidian artifacts in Oita Prefecture, where chert or rhyolite are common. The estimated source of obsidian is in Nagasaki or Saga Prefecture. In the Oita area, Hijiridaki is unusual in its set of types as well as its stone material.
(1) Artifacts unearthed in 1961 and 1962 include Late Palaeolithic types such as the trapeze of the middle phase, and microblades and microcores of the final phase, and even types of Late Jomon or later. The greater part of them have chipped edges with renewed patinas. A good hypothesis is that someone might have collected them in cultivated fields in northwest Kyushu and brought them to the cave sometime in the recent past.
(2) The fluorine content of the human cranium, unearthed in 1962 from the upper part of layer III, is 0.560%. The content of the newly recovered human bone (phalanges) unearthed in 1999, from about the same place as the cranium, is 0.529%. The content of the scapula of a badger (Meles meles), revovered from disturbed soil near the entrance, is 1.08%, and its radiocarbon age is 9940 ± 60BP (Beta-142915). Assuming all the sampls are from the same context, comparison of all the data indicates that the human bones are not older than a thousand years.
(3) Morphological study of the cranium is tentative so far, but it is only weakly similar to Pleistocene or Jomon craniums. On the other hand, its similarity with modern Edo period skulls is not necessarily weak. An example of a thick skull like the Hijiridaki one exists among Edo samples. The Hijiridaki cranium is thought unlikely to be of Pleistocene age.
For the past forty years, Hijiridaki cave has been known for its Pleistocene human remains and Palaeolithic artifacts. Now this distinction is denied. There is no positive proof of the archaic quality for the cranium or of a Palaeolithic context in the cave itself. A late Holocene or Medieval context is likely, but the lithic artifacts are still at issue.