Ancient Skeletons In Situ: Evaluating Bone Diagenesis at an Open-Air Archaeological Site and Community Museum in Central Thailand

Archaeological human skeletal remains are displayed in many museums across Thailand, under glass in exhibit halls, and as part of open-air displays where skeletons are partially excavated but remain in situ. This form of outdoor exhibit is a notable component of public archaeology initiatives and local educational outreach, but the potential long-term implications for bone preservation have raised concerns. This study investigated patterns of diagenesis at the Ban Pong Manao Archaeological Site and Community Museum in Lopburi Province, central Thailand, where some ancient skeletons are curated indoors in the on-site antiquities archive, and others are displayed outdoors in covered open-air excavation units. We applied a biogeochemical approach to investigate diagenesis, using methods from stable isotope analysis and Fourier-transformed infrared spectroscopy to assess post-excavation taphonomic processes. Results from this study revealed no statistically significant differences in values for bone collagen or bioapatite preservation indices between in situ and curated skeletons. However, we observed lower collagen yields and higher bioapatite carbonate yields among in situ skeletons that suggested processes of diagenesis may be accelerated by partial exposure in open-air display contexts. After roughly 20 years, differences between post-excavation contexts are not yet substantial but over time may increase if current taphonomic trajectories are maintained. We consider the implications and limitations of these results and examine partial excavation and exposure as simultaneously deleterious and additive in the context of cultural heritage management in Thailand.