In 2013, archeologists discovered the body of a 13th century farmwoman in a graveyard outside the former city of Troy in western Turkey. She sported strawberry-sized calcified nodules below her ribs, which they assumed were a sign of tuberculosis, a common disease for people of her era. But it turns out, they were wrong.
Physical and genetic analysis of the nodules suggest that they were likely abscesses from an infected placenta that led to the woman’s death—an exceedingly rare find in the fossil record. The results of the study were published recently in the journal eLife.
“There are no records for this anywhere,” Hendrik Poinar, of Canada’s McMaster University who extracted the DNA says in a press release. “We have almost no evidence from the archeological record of what maternal health and death was like until now.”
The woman's pregnancy likely assisted in preserving the genetic material, Meg Jones writes for the Milwaukee Journal Sentinel. The developing fetus requires a lot of calcium, so the extra minerals flowing through her body calcified the nodes of infection, preserving much more DNA than expected in an 800-year-old body, Caitlin Pepperell assistant professor of medicine and medical microbiology at the University of Wisconsin, Madison, who worked on the study, tells Jones.
“Calcification made little tiny suitcases of DNA and transported it across an 800-year time span,” Pepperell says in the release. “In this case, the amount and integrity of the ancient DNA was extraordinary. One typically gets less than one percent of the target organism.”
Identifying the infections, reports Jones, was something of a medical whodunnit. After archeologist Henrike Kiesewetter analyzed the skeleton and its nodes, she decided to send the little knobs to a classics professor and expert on the Trojan War. He then contacted Pepperell, who is an expert in tuberculosis. She realized the ancient infection was not TB and consulted with Poinar, an expert in ancient DNA extraction. Poinar was able to expertly extract the DNA of two pathogens, Staphylococcus saprophyticus and Gardnerella vaginalis, both of which cause urinary tract infections in women.
While the DNA of the Gardnerella has remained more or less unchanged since the Trojan woman was infected, Sheryl Ubelacker at The Canadian Press reports, the ancient Staphylococcus saprophyticus is more similar to modern strains of the bacteria that primarily infect cows. In the press release, Pepperell explains that people living in close proximity to animals in the past probably suffered from similar bacterial infections as their livestock. As humans have moved away from farm life, those bacteria have taken different paths.
“It seems to indicate that the strains that caused infection in Byzantine Troy are from a separate pool from the strains that cause human infection now," Pepperell tells Ubelacker. “Maybe if we looked in areas of the world where people live with their livestock now we would find a similar strain. We don't really know.”
While solving an 800-year-old medical mystery is interesting, Poinar says it’s more than just a curiosity. It could help researchers figure out how bacteria change and adapt and could lead to new forms of antibiotics, he tells Ubelacker. “It’s like capturing evolution in action in a fossil form that we rarely see.”