Abstract
First reported by Carl Wedl in 1864, microbial bioerosion is one of the most common and destructive taphonomic processes to act on skeletal material within the archaeological record. It refers to when microbes such as fungi, cyanobacteria, and bacteria breakdown mineralised hydroxyapatite to access bone collagen. Significantly lower prevalence rates for bacterial bioerosion in the bones of human and animal neonatal infants have been linked to the widely accepted sterility of foetal gastro-intestinal tracts, with the implication that infants who lack evidence for bacterial bioerosion did not survive long enough for their gut microflora to develop after birth. It is possible then, that assessments of microbial bioerosion in archaeological infant skeletal remains could be used to differentiate stillborn infants from older post-natal infants. Accurate age-at-death estimations for these individuals are important as infant mortality is considered to be a sensitive indicator of maternal and population health. The main aim of this thesis was to test the efficacy of micro-CT imaging to assessments of microbial bioerosion in archaeological infant skeletal remains from a tropical environment. This was achieved using a sample of eight infants from ‘Atele, a Chiefdom Period burial site in the Kingdom of Tonga. The second aim of this thesis was to provide insights into the biosocial context of the ‘Atele population within the Chiefdom period of Tongan culture history. Age-at-death estimations were calculated for these infants using a combination of dental and skeletal ageing standards. Micro-CT imaging was then used, as a non-destructive alternative to traditional histological techniques, to image the internal microstructure of a bone from each infant. Next, the micro-CT images captured were assessed for microibal bioerosion using the Oxford Histological Index. And lastly, the results of this assessment were compared to the results of previous research preformed on the ‘Atele skeletal collection. Of the infants assessed, all but one died within the first year of life. Three of these infants died within the first three months of life. The remaining individual was given an age-at-death of ca. 35.8 gestational weeks, suggesting it could have been a stillborn or premature infant. All the ‘Atele infants assessed displayed extensive evidence of bacterial bioerosion, including the possible stillborn individual discussed above. As the gastro-intestinal tract is believed to be rapidly colonised at birth, particularly through feeding, it is likely this individual was born premature and survived long enough after birth for at least its first feed. The level of perinatal and neonatal mortality within the ‘Atele population suggests that maternal health was being negatively impacted by some factor, likely a combination of nutritional and health related stress. The results of this study show micro-CT to be a valuable, non-destructive method for the imaging of the internal microstructure of bone for assessments of microbial bioerosion, however a certain degree of skill and experience is recommended to accurately interpret the information captured. This is particularly important when applying assessment methods developed for adult lamellar bone to images of infant woven bone. This study also supports the possibility of assessments of microbial bioerosion to be used to differentiate stillborn and premature infants from older post-natal infants. It also showed interesting potential for bacterial bioerosion to be used as a breastfeeding signal when used in conjunction with other methods such as stable isotope analysis. It may be beneficial to future research to test the results of this micro-CT assessment using traditional histological techniques.