Digging for Diseases

James Collins

ach morning, cheeks rosy from the wind, Jen Wagner would ride her bicycle from the artists' manor house where she was staying to the Southern Danish University campus in Odense, Denmark. The ride took half an hour, so brunsvier — a sweet breakfast pastry — and a cup of coffee were always a pleasant treat when she arrived. She would buy them at a bakery near the university, then head down to a basement lab — far away from Odense's spring sun and blossoming gardens — to continue examining an old collection of human bones.

Odense resembles a storybook village even though it's Denmark's third largest city. To most people it's famous because the fairy-tale writer Hans Christian Andersen was born there. Anthropologists like Wagner, however, know Odense for a different reason: The Anthropological Database at the university owns one of the world's largest collections of human skeletons, with 10,000 of them from the Medieval period alone.

The bones Wagner would study from March through May of 2001 were waiting for her when she arrived — packed away in stacked apple crates. Each crate contained bones from a single skeleton that had been excavated from sites throughout Denmark during the late 1960s and early '70s by several Danish archeologists. The ones Wagner was examining dated to roughly the 12th century. Some of the better preserved bones were found in wooden coffins. Others had been encased only by earth. All had been Danish peasants, supporting themselves for the most part by farming, and had died prior to the onset of the Black Death in Europe, at a time when leprosy was widespread.

Wagner's task was to search for signs of leprosy in the bones. With a bright lamp shining overhead, she would spread a crate of bones across a pool-table-green felt-covered lab bench. The felt caught the bone dust and cushioned the bones, helping to protect them from damage. No one before her had studied this particular collection, so she first needed to estimate age-at-death and determine sex. Various bones in a human skeleton provide clues to age. Jen examined characteristics of the teeth, the skull, the pelvis, and the long bones, for example, the bones of the legs. She would lift a tooth to the light to take a closer look it. She'd look at the size of the tooth, how developed the tooth's root was, and the position in relation to other teeth in the jaw. She would then lift the skeleton's humerus, the bone in the upper part of the arm that runs from the shoulder to the elbow. Perhaps it had a dent in it — a muscle marking. When muscles grow large, they create indentations in the bones. Typically a man would have a muscle that would create a dent like this, but as Wagner puts it, "it could have been a woman who just had different tasks." So, she would simply make note of the muscle marking on her sex-coding format sheet; later she would analyze all the data. "The more bones you have, the better your estimates are going to be," says Wagner. "One time, in the whole box, I had a humerus — that's it! It's just part of the game when you're dealing with archeological samples."

After noting estimates of age and sex, Wagner began focusing on signs of leprosy in the bones. Leprosy , also known as Hansen's disease, is a chronic infection that desensitizes the peripheral nerves in the human body. Ultimately, people who suffer from leprosy become physically mutilated as a result of the nerve paralysis. Signs of leprosy don't often show up in the bones. Out of the 196 skeletons Wagner looked at, a few might have been infected with leprosy in life, and five to ten percent of those few would have shown signs of it in their skeletons. "The lesions show up on the palette — the roof of the mouth — or on the tip of the little toe. It looks like someone took a pin and jabbed all over," Wagner observes. "In some cases, there's a rounding of the nasal aperture, which is the area between the nostrils on a human skull. The nasal spine can also become rounded or deteriorate entirely." Other signs of leprosy include bone swelling on certain bones and pimple-sized bumps on the tibia or fibula (the bones in the leg that go from the knee to the ankle) that make the surface of the bone look like the rough grain of a piece of wood.

In addition, leprosy itself may not be responsible for what paleopathologists, scientists who study ancient diseases, consider to be signs of the disease. Instead, the bones may have suffered damage in the soil or during excavation. "This makes paleopathology a guessing game — that's why people criticize it," Wagner remarks. Wagner's research is helping to validate paleopathology as a field; it provides a first step in being able to distinguish between leprosy and tuberculosis, both of which ran rampant in Europe during the 14th and 15th centuries. As the incidence of tuberculosis rose, the incidence of leprosy declined. Many scientists assume that a correlation exists between the rise of one and decline of the other — that the incidence of leprosy declined because the incidence of tuberculosis rose. By analyzing the data she collected in Denmark, Wagner hopes to help anthropologists better understand the link between these two diseases.

Wagner's research is part of a larger project developed Jesper Boldsen, head of the Anthropological Database at Odense University, and George Milner and James Wood, professors of anthropology at Penn State. Wood, who is Wagner's adviser, had been doing much of his research in New Guinea prior to becoming interested in Odense's collection of skeletons. An artifact from his travels in New Guinea — a female figure in a straw skirt — stares up from a corner in his office. The statue has four ear piercings, and as Wood comically puts it, "she's really become quite fashionable." Vast stacks of books about infectious diseases fill the remaining spaces in his office. In New Guinea, Wood studied the ways in which the local agricultural economy had affected health and population dynamics. On a sabbatical to Denmark seven years ago, Wood met Jesper Boldsen and decided to expand his research on human health by examining bones, using the skeletons at Odense.

In the future, Wood says, anthropologists will be able to better analyze skeletons. "In theory, we can go into old bone samples and retrieve pathogen DNA — we'll be able to build a detailed picture of the sex and age distribution of the disease," Wood states. Mark Shriver, professor of anthropology at Penn State, has developed an ancient-DNA lab just down the hall from Wood's office. Anthropologists working in the lab have already extracted human DNA from Medieval Danish bones and they believe they also have extracted DNA from an organism related to the bacterium that causes syphilis. The lab will concentrate on how various infectious diseases affected past populations.

Because very few diseases have skeletal lesions associated with them, DNA extraction in the ancient-DNA lab will allow paleopathologists to study a much wider range of diseases, including, for example, the bubonic plague, which many scholars (but not Wood) believe caused the Black Death in Medieval Europe. Traditional methods like those Wagner used in Denmark will be combined with newer methods whenever possible. According to Wood, anthropologists will continue to first visually examine bone surfaces when trying to detect leprosy and tuberculosis, and then if the bones show signs of either disease, scientist will attempt to extract DNA. "You can see reflections of experience in bones," Wood notes. "For instance, you can see the number of crises and the timing of them just by looking at layers of tooth enamel. When you see one of these skeletons, it's just incredible."

— Liliana M. Naydan

Jen Wagner received a B.A. in anthropology in May 2002, with honors in anthropology, from the College of the Liberal Arts and the Schreyer Honors College. Her anthropology adviser was James Wood, Ph.D., 517 Carpenter Bldg., University Park, PA 16802; 814-865-1936; jww3@psu.edu. Wagner's research was funded by the Schreyer Honors College, the College of the Liberal Arts, the Anthropology Department, Mark Shriver (RGSO Grant), and Phi Kappa Phi National Honor Society.