Although it has been hundreds of years since its initial outbreak in the 1300s, many of us are familiar with the infectious disease known as the bubonic plague (or black death), the most deadly pandemic ever recorded, wiping out a third of the European population.
An international team of scientists has now discovered that this devastating pandemic actually shaped human evolution, leaving a mark on our genetic makeup, still affecting our health 700 years later.
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The plague finds its origin in the fourteenth century but reappeared regularly on the continents Europa, Africa, and Asia in the centuries that followed. Although there are no more outbreaks in modern times, research published in the peer-reviewed journal Nature shows that the plague continues to affect our health to this date.
Scientists discovered a specific gene in the DNA of ancient skeletons with mutations that could explain why some people survived the plague while others didn't.
Linked to modern-day autoimmune diseases
The researchers examined a total of 206 remains (taking over 500 samples) of people who lived before, during, or after the Black Death pandemic. They looked for a particular genetic mutation related to the plague caused by a bacterium known as Yersinia pestis.
Researchers extracted DNA from the remains of people buried in the East Smithfield plague pits, which were used for mass burials in 1348 and 1349.
Credit: Museum of London Archaeology (MOLA) - Cropped for size by Universal-Sci
Interestingly it turns out that people with two identical copies of a particular gene, known as ERAP2, were 40 percent more likely to survive the plague compared to those with the opposing set of copies.
Those that survived the terrible disease passed the beneficial genetic adaptation on to their children, so the mutation continued to survive. Even today, the mutation is still common.
It turns out that genetic adaptation also contributes to the development of autoimmune diseases, such as Crohn's disease. In other words, the mutation that saved millions of lives hundreds of years ago still affects people's health.
The researchers stated that, over time, our immune systems have developed to react in different ways to pathogens, to the point that what had once been a protective gene against plague in the Middle Ages is today associated with heightened vulnerability to autoimmune diseases. ''This is the balancing act upon which evolution plays with our genome''.
Will the coronavirus have similar effects?
The scientists also looked at whether the corona pandemic could have a similar effect on our genetic makeup in the long term. But that is unlikely since SARS-CoV-2 mainly affects the health of the elderly. They often have already passed on their genes to their children before they become seriously ill or die.
It was the black deaths' capability to kill people of all ages and in huge numbers that made its long-lasting impact on our genetic makeup.
Nevertheless, according to Hendrik Poinar, author of the paper, comprehending the dynamics that shaped our immune system is vital to understanding how pandemics contribute to our susceptibility to disease in modern times.
Research like this may prove very valuable in our never-ending quest to understand the human immune system.
If you are interested in more details about the study published in the peer-reviewed journal nature, be sure to check it out listed below.
Sources and further reading:
Evolution of immune genes is associated with the Black Death (Nature)
Black Death (wikipedia)
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