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It is estimated that the historic pandemic killed more than half of the population in the most populated areas of Europe, Asia and Africa.
The black plague, caused by the ‘Yersinia pestis’ bacterium, is considered one of the pandemics deadliest
To identify the specific genetic differences between the survivors and the victims of the pandemic, as well as the way in which this event marked the evolution of the immune system, an international team of researchers analyzed 500 DNA samples from the 14th century, taken from plague victims buried in a London mass grave between 1348 Y 1349, as well as people who died before the arrival of the disease and survivors.
In particular, scientists looked for signs of disease-related genetic adaptation in the London population, zeroing in on a “window of 64 years before, during and after the Black Death, which reached in the middle of the decade of 1300.” After analyzing the samples, they discovered four genes
According to their results, published this Wednesday in Nature, individuals with two identical copies of the ‘ERAP2’ gene had between a 37 % and a 50 % more likely to survive than those without, so this characteristic was passed down from generation to generation, decreasing the mortality rate of the waves of bubonic plague, which would be repeated in the following centuries.
As this became less and less devastating, the alleles that provided protection against ‘death black’ continued to evolve. However, some of its current variants are associated with greater susceptibility to Cohn’s disease and rheumatoid arthritis, in which the immune system mistakenly attacks the body itself, destroying healthy tissue in the digestive tract and joints, respectively .
These results, the researchers note, provide empirical evidence of an association between autoimmune diseases and adaptation as a species to an infectious disease that wiped out much of the population .
“The selective advantage associated with the selected ‘loci’ is one of the strongest ever recorded in humans, demonstrating that a single pathogen can have a very strong impact on the evolution of the immune system” and, therefore, of humanity, pointed out Luis Barreiro, co-author of the publication.
