© Museum of London
Mass burial trench from the East Smithfield Black Death cemetery from London (MIN86).
In the middle of the 14th century, the Black Death swept Europe, killing millions of people, but archaeologists have recently discovered that its effects were far-ranging and surprising. People living after the plague were overall healthier than those who lived just before it, but a new study suggests that the Black Death may have caused Medieval women to shrink.

Writing in the American Journal of Human Biology, bioarchaeologist Sharon DeWitte from the University of South Carolina studied more than 800 skeletons from Medieval London with the goal of investigating "stress, sex, and plague." A bit less salacious than it sounds, the main topic covered in the research is the experience of physiological stress among members of two sexes -- male and female -- before and after the Black Death.

In examining skeletons from the 11th-12th century, the first half of the 13th century, and the mid-14th through mid-16th centuries, DeWitte calculated age-at-death from the bones and also tracked changes in the canine teeth and in the length of shin bones as a way of estimating people's health.

Using a mathematical survival analysis, DeWitte found that survivorship decreased before the Black Death but increased after it, for both males and females. That is, she found a general increase in health after the plague, explaining that "the post-Black Death demographic changes might represent a 'harvesting' effect; that is, an increase in mortality among people with compromised health."

Although generations following the plague were to some extent healthier than the ones before it, DeWitte was primarily interested in whether health outcomes were similar for males and females. She recorded the prevalence of linear enamel hypoplasia - a defect in the dental enamel caused by childhood stress such as infection - and found that these defects increased just before the Black Death and then decreased in the generations following it. This means that both male and female children suffered poor health prior to the plague, but later generations had better health.

© Sharon DeWitte / University of South Carolina
Enamel hypoplasia in a canine from the St. Mary Graces cemetery in London, dating to 1350-1540.
But the data DeWitte collected from shin bone length were a bit more puzzling. A person's adult height is produced by a complicated interaction between genes (taller parents tend to have taller children) and the environment (but if a kid with tall genes has poor childhood health, s/he may not reach their height potential). DeWitte found that male height significantly increased from the pre-plague to the post-plague time periods, which aligns with the overall picture of better health and survivorship after the Black Death.

Surprisingly, though, female stature decreased significantly in the two time periods. "These results," DeWitte notes, "suggest similar temporal trends in survivorship for both sexes but distinct male vs. female patterns of physiological stress before and after the Black Death."

What was happening to women and girls after the plague to cause them to shrink? DeWitte suggests a number of factors, including the possibility that females were better buffered from environmental stress than males before the plague or that males had better access to food after the plague.

Most intriguing, though, is DeWitte's suggestion that the decrease in female stature might reflect better nutrition following the plague. It is well known that in the period after the Black Death, standards of living in England improved considerably. The new shortage of laborers meant that wages increased to attract healthy workers and the price of food declined. More specifically, improvements in diet were seen across all social statuses, largely benefitting those lower-class people who previously did not have access to good food.

"If nutritional status or disease burden improved substantially following the Black Death in London," DeWitte suggests, "this might have resulted in earlier average age at menarche in the post-epidemic population and thus earlier cessation of growth in females." That is, better nutrition can lead to girls going through puberty earlier, which in turn can result in an earlier time at which they stop growing, making them shorter adult women. DeWitte emphasizes, though, that further work on establishing age at menarche is needed.

DeWitte's research is clear evidence that the health of post-plague generations was better than their pre-plague ancestors. However, she concludes by noting that these improvements "should not be viewed as evidence that the epidemic was ultimately good for affected populations. Any positive outcomes from the epidemic came at an unimaginably high cost in terms of the number of lives lost and the psychosocial stress experienced by the survivors." Rather, DeWitte intends her work on Medieval survivorship and health to help "identify factors that promote mortality crises and societal disruption, and that potentially can be addressed in living populations."

Kristina Killgrove is a bioarchaeologist at the University of West Florida. For more osteology news, follow her on Twitter (@DrKillgrove) or like her Facebook page Powered by Osteons.