Secrets from the grave

Centuries from now, if an archaeologist were to dig up Sharon DeWitte's bleached and weathered bones, they'd find a 7-inch stainless steel rod and nine screws buried among them.

These remnants of her childhood bout with scoliosis would not be the only window into the life she led.

Her flaming red hair and the rich tapestry of arm tattoos would be long gone. But the carbon and nitrogen isotopes in her molars would hint at her mostly vegetarian diet. Her stout, calcium-rich foot bones would offer clues that she was a runner. And a bony bump on her right patella, or knee bone, would serve as a legacy of the bad fall she took on a trail one summer.

While imagining one's remains may seem grisly, DeWitte has been doing it for as long as she can remember.

"Since I was a child I've been thinking about what happens to our bodies after we die and what stories people might make up about us based on what they find," said DeWitte, seated cross-legged in her dark gray office, plaster casts of two human skulls and a femur perched on a shelf near her desk.

A CU Boulder professor of anthropology and a pioneer in the niche field of bioarchaeology, she is now the one crafting those stories.

Through hours spent alone in museum basements, analyzing the fragile bones of those who died centuries ago in pandemics, she offers new insight into why some resist novel viruses and bacteria while others succumb to them. Her work also sheds light on how pathogens, like those during the Black Death, evolve and lend insight into the past lives of individuals, including women, children, the poor and racial minority groups.

"Skeletal evidence can provide us with information about people who aren't necessarily represented in most historical documents," said DeWitte, noting that those documents were often written by and about the wealthy and powerful. "I feel honored to be able to share something about people who were likely ignored while they were alive and are not represented in many surviving documents."

Revisiting the Black Death

In the spring of 2003, as tourists milled through the exhibits nearby, DeWitte pulled boxes containing complete human skeletons off the shelves in the Museum of London storage room. The museum's famed Centre for Human Bioarchaeology is home to thousands of centuries-old skeletal remains, excavated from burial grounds around the city.

DeWitte was particularly interested in those from Black Death cemeteries, mass graves proactively set aside in London in the mid-14th century as the bubonic plague marched across the European continent.

"They knew it was coming, and they knew it was going to be terrible," she said.

For months, she gingerly pulled the bones out of sealed plastic packages and placed them one by one onto a padded table to measure and inspect them.

As she explained, leg bone length can hint at someone's stature and nutrition status, while abnormal bumps indicate injuries or infection. Porous lesions around the eye sockets can be remnants of anemia. Horizontal stripes on the surface of teeth, known as linear enamel hypoplasia, can indicate episodes of disease or malnutrition, and thick plaque can provide hints about a person's hygiene or socioeconomic status.

"When you brush and floss your teeth, you're actually looking at your own skeleton," she said. "They are an amazing repository of information about our lives."

The humanity of it all was not lost on her. She was brought to tears when she opened a bag containing the tiny bones of an infant, or another in which mother and child appeared to have died together.

"I wondered, 'What were their last moments like together?' Every day I would see something so sad," she recalled.

She stressed that she is careful not to engage in the study of skeletal remains that are held against the wishes of descendant populations.

"I want to be sure the work I am doing never causes harm to living people."

The Marginalized Hit First and Worst

DeWitte has studied hundreds of skeletons, publishing numerous papers that paint a sometimes surprising picture of the world's most deadly pandemic. The Black Death did not, according to her research, kill indiscriminately. As with the COVID-19 pandemic, it hit marginalized communities, including the poor and the frail, harder.

"Premodern structural racism," as the authors call it, may have also played a role in determining who lived or died, suggests a new paper DeWitte and colleagues published in the journal BioarchaeologyInternational.

For the study, DeWitte and collaborators at the Museum of London and Brandeis University examined the bones of individuals buried in the East Smithfield emergency plague cemetery in the mid-1300s and those in two other London cemeteries that were not plague burial grounds. Using anthropological tools to estimate the population affinity of the deceased, they found significantly higher proportions of people of estimated African affinity in East Smithfield. Through further analysis, they concluded that Black women - who were often subject to misogyny and anti-Blackness and kept as servants in London at the time - were significantly more likely to die of the Black Death than people of white European descent.

"This research shows that there is a deep history of social marginalization shaping health and vulnerability to disease in human populations," said DeWitte.

Lessons from the Past

In other work, DeWitte collaborated with scientists to extract DNA from the teeth of Black Death victims. They found that the genome of Yersinia pestis, the bacteria that killed as many as 50 million people, is not all that different from that of bubonic plague varieties circulating today.

What made it so deadly?

More research is underway to help answer that question, but one possibility, DeWitte said, may have been climate change.

The 14th century marked the end of what some refer to as the Medieval Warm Period, a 400-year span in which relatively warm conditions were the norm and, across the Northern Hemisphere, people were able to broaden and diversify crops.

"As this warm period started to end, population growth outpaced agricultural production, and you had a growing share of resources and money concentrated into the hands of very few people," she said. "It was a lot like what you see today - climate change increasing social inequality, and then a new disease gets introduced."

A Brighter Future

Arizona State University anthropologist Jane Buikstra, who coined the term and founded the field of bioarchaeology, said DeWitte's work resonates in the era of COVID-19.

"Her work speaks to the issue of vulnerability and the fact that people who are disadvantaged, often through no fault of their own, are at special risk for these emerging diseases."

DeWitte joined CU's Institute for Behavioral Science in 2023 and has plans to expand her work to Northern China, where she will soon embark on a study at a 5,000-year-old site of "catastrophic mortality" - likely a plague.

Despite the seemingly dark nature of her work, she exudes warmth and optimism as she talks about its potential for good.

By identifying the structural inequalities that made certain groups more vulnerable to disease and death in past pandemics, she hopes her work can inspire modern society to tear down those inequalities.

Hopefully, before the next pandemic hits.

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