Identifying Paleolithic Hunting Targets with Synchrotron X-ray CT: Non-Destructive Analysis of Burnt Bone Fragments from Fukui Cave

A joint research group led by Professor Sumiaki Sawada of Niigata University of Health and Welfare (NSG Group) has succeeded in the non-destructive analysis of minute burnt bone fragments, dating back approximately 16,000 years, excavated from the Special Historic Site "Fukui Cave" (Sasebo City, Nagasaki Prefecture). This was achieved using high-resolution X-ray CT at the large synchrotron radiation facility SPring-8. Histological analysis of the bone tissue revealed a high probability that these bone fragments belong to medium-sized ungulates, such as deer and wild boar.

This achievement is of great significance as it not only demonstrates the actual state of animal resource utilization by humans at the end of the Paleolithic era but also helps elucidate the extinction process of large mammals like Naumann's elephants.

■ Overview

Non-destructive analysis of minute burnt bone fragments
Using high-resolution X-ray CT at the large synchrotron radiation facility SPring-8 (hereafter referred to as synchrotron X-ray CT), the team succeeded in non-destructively visualizing the internal bone structure of burnt bone fragments smaller than 1 cm excavated from late Paleolithic (approx. 16,000 years ago) strata in Fukui Cave, Nagasaki Prefecture.

Indicating potential derivation from medium-sized ungulates
Histological analysis of the bone's microstructure (osteons and Haversian canals) revealed a high likelihood that the excavated bone fragments originated from medium-sized ungulates such as deer and wild boar. Conversely, the possibility of them being bones from humans or large mammals like Naumann's elephants was negated.

A new method for analyzing fragmented bones
This technique, capable of extracting animal species information even from burnt bones with denatured DNA and proteins, is a new analytical method that contributes to understanding the relationship between humans and animals, as well as the extinction process of large mammals, in Japanese Paleolithic research where bone preservation is generally poor.

Analyzed burnt bone fragment (scale 5mm) / Burnt bone fragment CT image (scale 200μm, arrows indicate osteons)

■ Research Background

Although there are over 14,000 Paleolithic sites in the Japanese archipelago, the preservation state of bones is poor due to acidic soil derived from volcanic ash and the warm, humid climate, resulting in extremely limited cases of animal bone excavation. Consequently, what kinds of animals Paleolithic humans hunted has not been fully understood.

"Fukui Cave" in Sasebo City, Nagasaki Prefecture, is an important rock shelter site spanning the Paleolithic to the incipient Jomon periods. Burnt bone fragments have been excavated from strata dating to the end of the Paleolithic era (approx. 16,000 years ago). However, all of these were fragments smaller than 1 cm, making visual species identification impossible. Furthermore, analysis using DNA or proteins was difficult due to being baked at high temperatures.

■ Research Methods

In this study, to observe the internal structure without damaging the valuable bone specimens, synchrotron X-ray CT imaging was conducted at beamline BL20B2. After accounting for the effects of heat shrinkage on the obtained bone tissue images, they were statistically compared with various reference specimens—including elephants, Yabe's giant deer, sika deer, wild boar, bison, bears, and humans—to determine which animal the histological characteristics of the excavated fragments most closely resembled.

■ Major Findings

1. Successful non-destructive observation of bone microstructure
The team successfully observed bone microstructures such as "osteons" and "Haversian canals" non-destructively from burnt bones fragmented to less than 1 cm.

2. Confirmation of high likelihood of originating from medium-sized ungulates
Statistical analysis of the cross-sectional areas of osteons and Haversian canals indicated that the excavated bone fragments fall within the range of medium-sized ungulates such as deer and wild boar.

3. Negation of extinct large mammals and human origin
The possibility of originating from humans or large mammals that went extinct during the Paleolithic, such as Naumann's elephants and Yabe's giant deer, was negated.

4. Elucidation of hunting targets at the end of the Paleolithic
Contrary to the conventional image of "large game hunting," this study suggests that, at least in Fukui Cave at the end of the Paleolithic era, medium-sized ungulates like deer and wild boar were likely the targets of hunting.

■ Future Prospects

This research demonstrated that imaging technology using synchrotron X-ray CT can extract critical information capable of identifying animal species, even from fragmented burnt bones that were previously difficult to identify. This non-destructive analytical method is also highly useful from the perspective of cultural property protection. In the Japanese archipelago, which is unsuited for bone preservation, this research method is expected to become an effective approach for clarifying animal utilization by Paleolithic humans and the extinction process of large mammals.

■ Terminology

Fukui Cave: A rock shelter site in Sasebo City, Nagasaki Prefecture. Due to its importance in showing the transition from the Paleolithic to the Jomon period, it was designated a National Special Historic Site in 2024.

Large Synchrotron Radiation Facility SPring-8: A large synchrotron radiation facility that produces the world's highest performance synchrotron radiation, owned by RIKEN and located in Harima Science Garden City, Hyogo Prefecture. User support is provided by the Japan Synchrotron Radiation Research Institute (JASRI). The name SPring-8 stands for Super Photon ring-8 GeV. Various research, including nanotechnology and biotechnology, is conducted at SPring-8 using synchrotron radiation.