A research group including Assistant Professor Sasumu Aiko of the Department of Rehabilitation Sciences at Niigata University of Health and Welfare and Project Professor Suwa Gen of the University Museum, The University of Tokyo, has identified through comparative morphological analysis that the Ushikawa human bones, which had been thought to be one of Japan's Pleistocene hominin fossils, are in fact bear bones, making it clear that the "Ushikawa man" was not human.
The two Ushikawa bones were discovered in a limestone quarry in Ushikawa-cho, Toyohashi City, Aichi Prefecture, in 1957 and 1959, and were reported by Professor Emeritus Suzuki Takashi of the University of Tokyo as fossils of a human dating back to the Middle Pleistocene (78 to 1000 years ago). One was thought to be the left upper arm bone of a woman and the other the left femur of a man, but recent research has suggested that they may have been animal bones.
The research group observed the Ushikawa human bones and bear bones (11 brown bears and 13 Asiatic black bears) housed at the University Museum, the University of Tokyo, with the naked eye and a microscope, while also analyzing cross-sectional images taken with CT scans. As a result, they identified the woman's left humerus as the radius in the bear's forearm, and the man's left femur as the bear's femur.
The decisive factor was the rough surface structure unique to bear radii and the shape of the femoral head, which are similar to those of bears. The Ushikawa bones also date to the Late Pleistocene epoch, before about 2 years ago, and considering the distribution of mammals at that time, it was found that they were most likely from a brown bear.
The discovery of the Ushikawa bones was a major catalyst for the subsequent research into ancient humans. The research group believes that even if they are found to be bear bones, their academic significance will not change.
Furthermore, based on these results, apart from the fossils unearthed in the Ryukyu Islands, the only human fossil currently believed to belong to Japan's Paleolithic period is the Hamakita human bone discovered in Negataka Cave in Shizuoka Prefecture.
Paper information:[Anthropological Science (Japanese Series)] Identification of the parts and animal species of the "Ushikawa human bones" and a brief history of their study
