Abstract
Dental enamel formation is susceptible to physiological stress, resulting in permanent changes known as accentuated lines (ALs). This thesis explores the occurrence of accentuated lines (ALs), in the dentition of two nineteenth century archaeological assemblages; migrant adults (n = 45) and colony-born children (n = 10) interred in New Zealand (c. 1857-1904 AD) and adults (n = 9) and children (n = 16) interred in London, United Kingdom (c. 1821-1853 AD), alongside a group of contemporary children (n = 28) from Dunedin, New Zealand. Accentuated lines are widely interpreted as a biomarker of lived stress or hardship during infancy and childhood, and can illuminate associations between health, infant development, and an individuals’ broader environment. The Developmental Origins of Health and Disease (DOHaD) paradigm highlights the first few years of life as notably vulnerable and plastic, and adversity in childhood is known to have lifelong ramifications.
During the nineteenth century, many working-class peoples experienced declining health and living conditions in association with growing industrialisation and urbanisation. Emigration to British colonies, such as New Zealand, was sold as a means to escape hardships and to improve future prospects. In this thesis, ALs were observed in almost all archaeological samples, however, patterns of AL formation varied between adults of different ethnic and geographical background. Differences in AL occurrence in relation to key biological life stages were also observed, consistent with expectations under DOHaD.
Although ALs are commonly presented as a proxy of stress, many factors may influence enamel formation, making interpretation of potential aetiologies difficult. The analysis of modern children with known maternal and medical histories in this thesis highlights the need to incorporate multiple lines of evidence when interpreting AL occurrence. In this study, it was found that 65% (54/83) of the ALs observed in 86% (24/28) of modern participants, potentially occurred contemporaneously with a documented stressor, including vaccination, introduction of solid food, dental eruption and cessation of breastfeeding. These findings illustrate the value of integrating contextual and biological data to interrogate impacts on dental growth and development. Overall, this thesis demonstrates the usefulness of bioarchaeological research in reconstructing life experiences, even in poorly preserved archaeological samples. However, considering an individuals’ wider environment alongside using theoretical frameworks such as DOHaD can enrich and improve interpretation of ALs as a proxy of stress.