Black Death victims offer clues to childhood malnutrition and adult disease

The Black Death arrived on the shores of England in May 1348 and, in less than two years, spread throughout the country, killing an estimated 2 million people. The death toll from the disease, which was caused by the bacterium Yersinia pestis, got so high that officials in London and other cities opened new cemeteries where hundreds of bodies were interred every day. 

According to a new study, those who died around the time of the Black Death may help scientists answer a decidedly modern question: How can malnutrition early in life shape the health of humans far into adulthood?

The answer may be more complicated than scientists once suspected, said Sharon DeWitte, lead author of the study and a professor in the Institute of Behavioral Science and Department of Anthropology at the University of Colorado Boulder. 

In the new research, DeWitte and her colleagues examined chemical clues hidden in the teeth of nearly 275 people buried in English cemeteries before, during and after the Black Death. The team discovered something surprising: People who experienced malnutrition early in their lives may have survived threats to their health, like plague, at greater rates than their peers up until young adulthood, or roughly before the age of 30.

Those survival advantages, however, could have dropped significantly when the same individuals entered their middle and late adult years.

What this might indicate is that if people experienced a period of starvation early in their childhoods or adolescence but survived, that could have shaped their development in ways that were beneficial in the short term but led to poor outcomes once they got older,"

Sharon DeWitte, lead author of the study and professor in the Institute of Behavioral Science and Department of Anthropology, University of Colorado Boulder

She and her colleagues will publish their findings July 30 in the journal Science Advances.

The research is part of DeWitte's ongoing effort to understand the past to help humans living today. 

"Mortality varied during a catastrophe 700 years ago in ways that might have been preventable," she said. "My hope is that we can absorb that lesson and think about how human health can vary across different social categories today, and figure out the points of intervention where we can do something to reduce that burden."

Childhood health

How experiences early in life shape our health long into the future is far from clear cut.

Some studies of modern humans, for example, have linked low birth weights in infants to health problems later in life. Babies born small, a possible sign of nutritional stress, seem to be more prone to illnesses like cardiovascular disease and diabetes in adulthood than the population at large.

The Black Death, sometimes known as the second pandemic of plague, might be an ideal laboratory for studying these questions, DeWitte noted. In part, that's because the death toll around Europe varied drastically-in some parts of England, for example, about 30% of the population died, while mortality rates reached 75% in Florence, Italy.

"It raises questions about why mortality was higher in some populations than others," she said.

To pursue those questions, DeWitte and her colleagues turned to teeth.

Environment matters

She explained that what humans eat as infants and children leaves a mark in the development of our adult teeth-subtly shifting the types, or "isotopes," of carbon and nitrogen atoms present in the dentine. In particular, when people experience extreme nutritional stress, their bodies will begin to break down their own fat stores and muscle, which have a different signature of isotopes than food that is eaten.

In the current study, DeWitte's team examined the isotopes present in the teeth of hundreds of people buried in English cemeteries between 1100 to 1540 AD. They included the East Smithfield Black Death Cemetery, which opened in London in 1348 and where the bodies of hundreds of plague victims were stacked in a mass burial trenches.

DeWitte emphasizes that the team's results are far from definitive-in many cases, the group doesn't have any records about the humans included in the research, so it's hard to know for sure how they died or how healthy they were in life.

But the findings carry hints that malnutrition early in life may shape the health of adults in ways that aren't necessarily good or bad-it all depends on context. 

When infants or children don't have enough to eat, DeWitte said, their bodies may develop in ways that prime them for hardship later in life. They may have altered metabolism, for example, so that they use calories, which may be scarce, more efficiently.

Those changes can be beneficial-that is, until the environment changes and food becomes more plentiful. Some evidence, for example, suggests that in the wake of the Black Death, conditions for survivors in England improved as laborers demanded higher wages.

"People who experienced nutritional stress as children may have had a mismatch with their environments later in life," DeWitte said. "If there's now a resource abundance, but their bodies were shaped for an environment of scarcity, they may have poor health outcomes, like packing too many fat stores, which can lead to cardiovascular disease."

For DeWitte, the study is another example of what humans living today can learn from people who died hundreds of years ago:

"For a very long time, I've been interested in this question of why some people experience good health and others living in the exact same society don't."