The Mass Grave (1850s)

Almost a year after Vercellotti first tapped his trowel on the bed of lime, he and a crowd of students set to the task of systemically uncovering the entombed skeletons in area 1000. They chipped away the cementlike lime and tried to avoid inhaling the powdery white dust. Once they broke through the shell in early July, they brushed and scooped away the soil, sometimes with teaspoons. They found that each skeleton was buried separately, but all were blanketed in lime.

One skeleton clutched a cross, head to the side, jaw agape. Another had a twisted spine, likely evidence of scoliosis. All had been buried in shrouds and were lying in unusual positions as though they had been dumped hurriedly. Everything fit the hypothesis that they were victims of an epidemic.

The researchers carefully uncovered another exceptionally complete skeleton—an older woman, as shown by her frail bones and worn teeth. She was lying on her side, probably in the same position in which she died. In the soil beneath her, they could see the impression of her fingers and ear, and the lines left by her bodice’s laces. “I loved excavating her,” Vercellotti said. “She was beautiful,” Gino Fornaciari agreed. Beneath her skull, they found a single, golden hoop earring, and they began to call her the Lady with the Gold Earring.

That earring was a clue: This was no medieval matron. The hoop style, as well as buttons and fasteners for clothing found with other skeletons, showed that these people died in the mid-1800s—too late to be victims of the Black Death. So what did kill them?

To find out, Poinar and Vercellotti pulled teeth from their skulls and scooped soil from where their stomachs once lay, seeking to sample and identify the pathogen’s DNA. They already have a working hypothesis: cholera.

In 1855, this terrible diarrheal disease, transmitted by the waterborne bacterium Vibrio cholerae, swept through Italy, part of a worldwide pandemic. Poinar is just as eager to find DNA from V. cholerae as from plague, because tracing the evolution of cholera is still urgent today.

Like other pathogens, V. cholerae keeps evolving into new forms, and it continues to erupt into worldwide pandemics. Since the 1960s, the seventh known pandemic has infected 3 million to 4 million people and killed nearly 100,000 every year, with a new strain causing particular devastation in Haiti recently. If researchers can trace the bacterium’s evolutionary history, they might be able to identify the key mutations that trigger virulence or adaptation to different habitats, for example. This could help them design better vaccines or medicines.

Poinar has already sequenced a sample of mid-19th century cholera from the United States. The researchers gathered DNA from a cholera victim’s intestines, which in 1849 were preserved in jars in the Mütter Museum in Philadelphia. Their unpublished results match that strain with those that caused pandemics from 1899 to 1923; all these strains differ from the El Tor strain that swept Haiti last year. If Poinar gets cholera DNA from Pozzeveri, it will let him compare the Philadelphia V. cholerae genome with one from the same time but a different place.

After extracting DNA from many of the 40 teeth he gathered at the site, Poinar sent samples to the Lawrence Livermore National Laboratory in California. There, the DNA is being scanned with a new microarray that can detect DNA from 3000 different pathogens, including the microbes that cause plague, TB, malaria, syphilis, Lyme disease, and cholera.

Despite the unexpected bonus of a probable cholera epidemic, Poinar was still intent on finding plague victims. On his last day at the site, he kept going back to the medieval trench, where the teeth peeped tantalizingly from the wall. Vercellotti gently brushed dirt off the jaw and sprayed it with water, hoping to loosen the sediment. But the jaw wouldn’t budge. He finally gave up. “Next year,” he promised. Poinar left Italy still haunted by hopes of a plague sample.

Two weeks later, when he returned to his lab in Canada, he got a tiny package from Vercellotti. It held the tooth he had wanted so badly. Vercellotti had managed to excavate it in the season’s final week, and its DNA is now being analyzed.