In 2003, workers building a highway through a small town in Ireland came across a long-lost medieval cemetery.
Of the approximately 1,300 bodies found at the site near Ballyhanna township, a few of the old burials stood out. Their bones were riddled with benign tumors caused by a rare disease, but for strangely different reasons.
Both individuals appeared to have a genetic condition known as multiple osteochondromas, which causes painful but usually noncancerous tumors to grow in the bone, leading over time to limb deformity, postural problems, or nerve damage.
Today we know that the disease is far from common, occurring in about one person in 50,000. Finding two bodies with the condition in such a small cemetery is quite a coincidence, especially since a genome analysis of the remains has been published in the European Journal of Human Genetics discovers that the two men who left the bones were not closely related.
In fact, their lives were several centuries apart in this small Irish parish.
“We had different assumptions about these two men when we first realized they had both suffered from multiple osteochondromas,” explains Queen’s University Belfast archaeologist Eileen Murphy, a senior author on the study.
“We assumed they were contemporary, but radiocarbon dating showed them to be several hundred years apart. We also assumed they were related, but the new [ancient DNA] analysis has shown that this is not the case.”
None of the skeletons excavated from the lost graveyard of the Ballyhanna look like they were in particularly good health when they died. Some show signs of tuberculosis or rickets.
But the bones of the two men with bony spurs were in particularly bad health.
Archaeologists suspect that the graveyard was once part of a lower-class Gaelic medieval community made up of men, women and children. Some individuals were probably very poor, while others worked as farmers, labourers, merchants, artisans or clergy.
The discovery of two unrelated men with the same rare bone disease in such a small community is unusual in itself, and it gets weirder.
Despite their similar appearance, the recent analysis revealed that the two cases of multiple osteochondroma were not even caused by the same genetic mutation.
The individuals both showed changes in the EXT1 gene, which is linked to multiple osteochondromas. But one of the mutations has never been seen in modern patients.
The first man had a missense mutation in part of his EXT1 gene, where a single nucleotide base was swapped for another, scrambling the encoded sequence for the protein. It has previously been identified in at least three modern patients with multiple osteochondromas.
The second man showed a premature stop message in the same gene that has not yet appeared in modern sequencing data from patients with the disease.
The person with the new mutation died at a younger age, around 18 to 25, and showed deformities in his hips, knees, ankle and forearm. He lived sometime between 1031 and 1260 CE.
The person who died at an older age, around 30 or 40, had less pronounced tumors, but they were visible all over his skeleton. He lived between 689 and 975 AD.
“It was really surprising that these individuals had completely different mutations that caused their condition, especially since it’s so rare,” says geneticist and first author Iseult Jackson of Trinity College Dublin.
The discovery just goes to show how much modern DNA analysis can reveal about diseases that have plagued us for millennia.
“The study shows the important contribution that ancient DNA analysis of people from the past can make to understanding conditions that still affect people today,” says geneticist Dan Bradley from Trinity College Dublin.
The research has been published in the European Journal of Human Genetics.