Our mediaeval ancestors may have passed on to us the genes that helped them escape the Black Death pandemic, but these genes are now making us more susceptible to certain diseases, according to a study published on Wednesday in the journal Nature.
In the study, the changes that let people survive the plague that swept over Europe and killed at least 200 million people were discovered by analysing the DNA of centuries-old skeletons. However, auto-immune conditions including lupus, rheumatoid arthritis, and Crohn’s disease are associated with the same abnormalities.
These illnesses cause the immune system, which normally protects our bodies from illness and infections, to turn against us and begin attacking the body’s own healthy tissues. Professor of anthropology Hendrik Poinar of McMaster University in Ontario and senior author of the study said, ‘A hyperactive immune system may have been great in the past, but it might not be as helpful in the environment now.’
The Black Death, which swept through Europe, the Middle East, and northern Africa in the 14th century and killed up to 50% of the population, was the single deadliest incident in recorded human history.
According to research, seismic occurrences must have had an effect on human evolution. The researchers concluded that this study demonstrates how bacteria gradually change humans.
While past research has sought to examine the effect of the Black Death on the human genome, this study shows the significance the plague had on the evolution of the human immune system, said Barreiro.
Furthermore, a unique aspect of this research, he added, was to focus on a narrow time window around the event.
However, the more recent Covid-19 pandemic will not leave a similar legacy on human evolution, said the senior author, attributing this to the much lower death rate when compared to Black Death.