Comparisons of mean survival rates show that when the Black Death hit in 1348, people’s general health had for some time been deteriorating

Setting the stage for medieval plague: Pre-black death trends in survival and mortality
Sharon N. DeWitte
In: American Journal of Physical Anthropology (2015) Volume 158, Issue 3, pages 441–451

ABSTRACT:

The 14th-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 14th 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, 11–12th centuries vs 13th century CE, to determine if demographic conditions were deteriorating before the epidemic occurred.

The study has been done using a sample of individuals from several London cemeteries that have been dated, in whole or in part, either to the 11–12th centuries (n = 339) or 13th 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.

The age-at-death distributions from the two pre-Black Death time periods are significantly different, with fewer older adults in 13th century. The results of Kaplan–Meier survival analysis indicate reductions in survival before the Black Death, with significantly lower survival in the 13th century (Mantel Cox p < 0.001). The analysis has shown that while the mean survival rate for people in the early pre-plague period was 38.19 years, the late pre-plague rate was only 31.63; a reduction of nearly a fifth. Last, hazard analysis reveals increases in mortality rates before the Black Death.

Together, these results suggest that health in general was already declining in the 13th 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.

ABOUT THE AUTHOR:

Sharon N. DeWitte is at the Department of Anthropology, University of South Carolina, Columbia, SC

FEATURED PHOTO:

The bodies of thousands of Londoners including plague victims, lie in the Bedlam Burial Ground
© Courtesy of Crossrail