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In the mid-1300s, fleas carrying the bacteria Yersinia pestis caused the bubonic plague to spread across Europe, North Africa, and the Middle East. As many as 50% of people in those regions lost their lives to history’s deadliest known pandemic, the Black Death. Yet despite the unprecedented death toll, many individuals managed to survive. The findings of a recent study, published in October 2022 in Nature, support a long-held hypothesis that plague survivors had certain favorable genetic advantages.
A team from the University of Chicago, McMaster University, and the Institut Pasteur collected and analyzed ancient DNA from the remains of people who lived before, during, and after the Black Death in England and Denmark. Arguably the most notable finding was the increased prevalence of a protective variant of the pathogen-fighting ERAP2 gene in people who lived after the Black Death. The researchers found that people who had two copies of this gene variant, as opposed to one or zero copies, were up to 40% more likely to survive.
The genetic legacy of the Black Death:
- The researchers were able to test their findings in laboratory conditions by exposing immune cells to Yersinia pestis. The cells with two copies of the favorable ERAP2 variant were much more successful at defeating the bacteria.
- The findings are an incredible example of natural selection in action. In just a few generations, the proportion of Londoners with at least one favorable copy of the gene increased from 40% to over 50%.
- It’s not all good news, though, for people who have inherited the superior pathogen-fighting variant of the ERAP2 gene. This variant has also been linked to autoimmune diseases such as Crohn’s disease and lupus, though it is important to note that many different factors determine whether an individual has an increased risk of certain conditions.