Endocranial restoration and volume estimation of the Minatogawa IV cranium using micro-CT and 3D printer systems

The Minatogawa IV cranium is one of three well-preserved Late Pleistocene Homo sapiens crania from the Minatogawa fissure site, Okinawa Island. This cranium is more damaged than Minatogawa I and exhibits some clear post-mortem distortion. We reconstructed the endocranium of this specimen after correcting the distortion and breakage by combining digital and manual restoration procedures, and established a reliable estimate for its endocranial volume (ECV) to be around 1170 cc. As with the case of Minatogawa I, this result confirmed the suggestion of previous work that the Minatogawa series has small ECVs compared with modern Japanese and Jomon populations. Some dental and osteological conditions, such as heavy tooth wear as well as Harris's lines of the long bones, suggest a possibility that the small ECV of the Minatogawa people as well as their short stature might have been caused in part by a stunting of growth due to undernutrition and possibly a microevolutionary adaptation to the food-limited insular environments.