Oral Health and the Intensification of Agriculture at Ban Non Wat, Thailand

Abstract

Many bioarchaeological studies have found a general decline in oral health with intensifying agriculture, which has been attributed to an increased reliance on a starchy carbohydrate staple and decreased dietary breadth. This evidence has contributed to a widely accepted 'agricultural model' for oral health change in prehistory, which posits a global positive correlation between the transition to and intensification of agriculture and a marked increase in rates of oral pathology, especially dental caries. This decline in oral health was often more dramatic for females, which is usually attributed to dietary differences associated with the sexual division of labour. However, this model is based mainly on prehistoric populations from the Western hemisphere, most notably maize agriculturists from North America, and presents a rather simplistic relationship between diet and oral health. Moreover, recent research from Southeast Asia does not fit this pattern, showing no clear decline in oral health with the development of intensive rice agriculture. These observations from prehistoric Southeast Asia are however based on relatively small skeletal assemblages and represent a synthesis of data from multiple archaeological sites rather than a single occupational history.

This thesis aims to address these issues by investigating whether or not there is a relationship between oral health and the intensification of rice agriculture and associated sociopolitical and environmental changes at the prehistoric site of Ban Non Wat in the Upper Mun River Valley (UMRV) in northeast Thailand. This site has a long cultural sequence that spans the development of intensive rice production from the Neolithic to the Iron Age (1750 BC – 500 AD) and a large relatively well-preserved skeletal assemblage. It therefore offers an ideal opportunity to test the agricultural model for oral health change using a diachronic perspective and evaluate its appropriateness in the context of Southeast Asia with the intensification of rice agriculture.

The oral health status of the population is based on several dental pathologies that are sensitive to diet. These include: dental caries, advanced tooth wear, tooth infections, periodontal disease and calculus, and antemortem tooth loss. These oral pathologies were diagnosed using both visual (macroscopic) and radiographic methods. The results of the visual and radiographic assessments are integrated and evaluated in relation to aspects of the local environment that may have impacted on oral health, namely diet and nutrition, subsistence practices, female reproductive biology, demographic changes and social organisation.

The results show a fluctuating pattern of oral health change from the Neolithic to Iron Age at Ban Non Wat. In general, oral health appears to have been relatively poor in the Neolithic, improved in the Early Bronze Age and deteriorated in the Late Bronze and Iron Age phases though the oral health profiles in each time period are quite different. Although there is no clear linear relationship with more intensive agricultural practices, the temporal variations in oral health at Ban Non Wat possibly reflect changes in dietary and subsistence practices. It is also likely that other factors were involved such as changes in social organisation and resource management in response to deteriorating environmental conditions. With regard to the relative oral health of males and females in each time period, results show that female oral health was consistently worse than males during the intensification of rice agriculture. However, with the exception of tooth infections, sex differences did not increase over time. Although diet was likely a factor in the different oral health profiles for males and females at Ban Non Wat, underlying physiological factors may have also contributed to this pattern. The results of this thesis do not follow model predictions for declining oral health with the intensification of agriculture and provide new evidence that the agricultural model is not universally applicable. The thesis shows that oral health changes with the intensification of agriculture are complex and specific to local environments.