Looking at the teeth of adults can tell us a lot about early life-histories and unlock the secrets of the living conditions of past communities. An open access study published in the International Journal of Paleopathology aimed to give insight into the environmental and social changes seen in medieval Denmark, a time associated with the late medieval agrarian crisis and the mid-14th century Black Death epidemic.
The authors used microscopic techniques to measure instances of stress in the teeth which form as the result of infection and/or poor nutrition. Teeth are especially useful for this analysis of stress as enamel forms at regular periodicity and permanent irregularities are formed when there is growth disruption from a stressful episode. Enamel growth lines visible on the tooth surface (known as perikymata) can be seen internally, and when these lines are pronounced (accentuated striae of Retzius or AS), these are associated with growth disruption. This type of analysis is especially useful as it is becoming recognised that assessing enamel defects with the naked eye is subjective, resulting in inter-observer error in quantifying these defects.
Mandibular canine with an example of an accentuated striae of Retzius (AS) highlighted by A (red arrows). Figure from Gamble et al. 2017.
The sample (n=70) used in this research was from the rural cemetery of Sejet and the urban cemetery of Ole Wormsgade, near the mediaeval market town of Horsens, dating from between mid-12th and mid-16th centuries.
Results showed sex differences in survivorship and stress experience. In males more stress is associated with reduced survivorship and in females more stress is associated with increased survivorship. These results are supported by previous studies investigating enamel defects and mortality in mediaeval England (e.g. De Witte 2010), which have been interpreted in the context that stress will have an adverse impact on later life health and in particular on males. Or, the authors argue, cultural factors resulting in different treatment of males and females may be a factor to explain these results.
It should be noted that the individuals used in this study survived past childhood so are not necessarily representative of the frailer individuals who died prematurely. The authors argue that “the late medieval agrarian crisis in association with episodes such as the Great Bovine Pestilence and consequent periods of famine may have interacted in a complex fashion with individual frailty for the populations in this study. Evidence points to increased morbidity and mortality prior to Black Death in England, along with selectivity in response to pre-existing health conditions as part of the Black Death epidemic. It is possible that less frail individuals who survived more stress events were able to mount a stronger immune response to pathogens later in life, thus conferring an advantage that would contribute to greater longevity.”
I wonder if further work done on AS in deciduous teeth (from the non-survivors) that form in-utero and during infancy could tease apart some of these interpretations of frailty and sex of the survivors in this study.
DeWitte, S. N. (2010). Sex Differentials in Frailty in Medieval England. American Journal of Physical Anthropology, 143 (2): 285–297.