Soil surrounding centuries-old skeletons can reveal how the deceased people spent their last day on Earth, according to a new study published in the journal Heritage Science.
Danish researchers used the new technology to investigate the remains of a 10- to 13-year-old child who had been buried in the medieval town of Ribe, in Denmark, some 800 years ago.
According to their findings, the day before death was indeed painful for the poor child, who was likely suffering from a severe illness. In a desperate attempt to save his or her life, the child was given a high dose of bacteria-killing mercury.
“I cannot say which diseases the child had contracted.” Kaare Lund Rasmussen, a chemist from the University of Southern Denmark, said. “But I can say that (the child) was exposed to a large dose of mercury a couple of months before its death and again a day or two prior to death.”
“You can imagine what happened: that the family for a while tried to cure the child with mercury-containing medicine which may or may not have worked, but that the child’s condition suddenly worsened and that it was administered a large dose of mercury which was, however, not able to save its life,” he added.
The detailed insight into the life of the child did not come from analyses of the child’s bones. Rather, Rasmussen and colleagues extracted the crucial information from the soil surrounding the skeletal remains.
The sampling technique relies on the compounds released when a body decays in the grave.
“If we can localize an element in the soil in the immediate vicinity of the skeleton which is not normally found in the soil itself, we can assume that it came from the deceased and this can tell us something about how the person lived. We are not interested in death, but in the life before death,” Rasmussen said.
The soil samples must be taken from the regions once occupied by the individual’s lungs, kidneys, liver and muscle tissue.
For example, the compounds that were originally part of the kidneys have now become part of the soil — provided they have not been washed away by groundwater.
“If there was mercury present in the kidney at the time of death it would have been transformed rapidly to mercury sulphide, which is very immobile and undissolvable in water. In this way we can obtain information about the deceased even though we do not analyze the bones,” Rasmussen said.
Locating the compounds in relation to the decayed organs is very important to get clues about the last days of the deceased. For instance, mercury is excreted very fast from the lungs, within hours or at the most a couple of days.
“When we found high mercury concentrations in the soil that had once been the lungs of the child, we could conclude that the child probably was exposed to mercury within the last 48 hours or so before its death,” Rasmussen said.
Although bones can also be analyzed for excess mercury, the technique has some limitations, according to Rasmussen.
“While the soil gives insight into the last months and days before death, the bones can only give information about the mercury exposure from about 10 to three years prior to death,” he said.
Rarely found naturally in soil, mercury is particularly interesting for archaeologists as many cultures in different part of the world have been in contact with this chemical element.
In medieval Europe, mercury was used for centuries in the color pigment cinnabar, which was employed for illuminating manuscripts by medieval monks. Since Roman times mercury was widely applied as the active ingredient in medicine administered against a variety of diseases. Such treatment was practiced well into the 1900s — for instance, the Danish novelist Karen Blixen received it in 1914.
“Mercury is extremely toxic and surely some died from mercury poisoning and not the ailment it was meant to cure,” Rasmussen said.
Rasmussen and his colleagues have already used the technique on soil samples from 19 medieval burials in the Lindegaarden cemetery in Ribe and Ole Wormsgade in Horsens, Denmark.
Image: Sampling holes in the soil are placed in the position of the lungs, liver, kidney and the muscles of the upper arms. Credit: County Museums of Odense