Setting the stage for medieval plague: Pre-black death trends in survival and mortality.

OBJECTIVES The 14(th) -century Black Death was one of the most devastating epidemics in human history, killing tens of millions of people in a short period of time. It is not clear why mortality rates during the epidemic were so high. One possibility is that the affected human populations were particularly stressed in the 14(th) century, perhaps as a result of repeated famines in areas such as England. This project examines survival and mortality in two pre-Black Death time periods, 11-12(th) centuries vs 13(th) century CE, to determine if demographic conditions were deteriorating before the epidemic occurred. MATERIALS AND METHODS This study is done using a sample of individuals from several London cemeteries that have been dated, in whole or in part, either to the 11-12(th) centuries (n = 339) or 13(th) century (n = 258). Temporal trends in survivorship and mortality are assessed via Kaplan-Meier survival analysis and by modeling time period as a covariate affecting the Gompertz hazard of adult mortality. RESULTS The age-at-death distributions from the two pre-Black Death time periods are significantly different, with fewer older adults in 13(th) century. The results of Kaplan-Meier survival analysis indicate reductions in survival before the Black Death, with significantly lower survival in the 13(th) century (Mantel Cox p < 0.001). Last, hazard analysis reveals increases in mortality rates before the Black Death. CONCLUSIONS Together, these results suggest that health in general was declining in the 13(th) century, and this might have led to high mortality during the Black Death. This highlights the importance of considering human context to understand disease in past and living human populations.