Scientists have revealed that genetic traits that once protected humans from the Black Death are now linked to increased susceptibility to autoimmune diseases.
DNA analysis of victims and survivors from the plague outbreak in the 14th century shows that those with a “beneficial” variant of a specific gene known as ERAP2 had a significantly higher survival rate, according to a report by the Guardian.
Scientists sampled remains from graves at three cemeteries in London. (Photo: Museum of London Archaeology).
These findings shed light on how the Black Death—an epidemic that wiped out about 50% of Europe’s population—shaped the evolution of immune genes like ERAP2. This, in turn, influences how humans respond to diseases today.
Researchers note that the ERAP2 variant also poses a risk factor for Crohn’s disease and is associated with other autoimmune diseases. It is considered a “selectively beneficial variant.”
Many Europeans carry the gene mutation that protected their ancestors from the plague, scientists reported on October 19 in the journal Nature.
Certain genetic variants are believed to enhance human survival after this epidemic. However, this protection comes at a cost: individuals inheriting mutations resistant to the plague face a higher risk of developing immune disorders such as Crohn’s disease, according to the New York Times.
Crohn’s disease is a disorder in which the immune system attacks friendly bacteria in the gut, leading to inflammation.
Luis Barreiro, a professor of genetics at the University of Chicago Medical Center and a co-lead author of the study, stated: “This is the first evidence showing that the Black Death was indeed a significant selective pressure on the development of the human immune system.”
For this study, over 500 ancient DNA samples were extracted from remains, including those buried in the East Smithfield plague pit in London. These samples were taken from individuals who died before, during, and after the Black Death.
Individuals with this variant had approximately a 40% higher chance of surviving the Black Death compared to those without it.
Commenting on the risks associated with this gene variant, Hendrik Poinar, a professor of anthropology at McMaster University in Canada and a co-lead author of the study, said: “These are unfortunate side effects of the selection process that provides long-term protection.”
Although the plague has infected humans for thousands of years, it struck medieval Europe with such intensity that scientists wonder whether the Black Death changed the genetic makeup of Europeans.
“We expect to see a significant change,” Poinar remarked.
