How the Black Death Changed European DNA Forever

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How the Black Death Changed European DNA Forever…

In the mid-14th century, Europe was hit by one of the most devastating events in human history: the Black Death. Between 1346 and 1353, a microscopic bacterium—Yersinia pestis—spread across continents, killing tens of millions and reshaping societies overnight. But what was the genetic impact of the Black Death and how is it still felt in peoples DNA today?

Now the origins of the pandemic is linked to Central Asia, likely around the Tian Shan mountain ranges, that run through modern-day Kyrgyzstan and other countries. From there, the disease moved westward along trade routes like the Silk Road, eventually reaching the Black Sea. In 1347, it entered Europe via merchant ships arriving in Mediterranean ports, and from that moment on, it spread with astonishing speed.

Within just a few years, it had reached nearly every corner of Europe. The mortality was catastrophic. Estimates suggest that between 30% and 60% of Europe’s population died—roughly 25 to 50 million people. Entire communities vanished, and normal burial practices collapsed under the sheer number of dead.

Yet the plague did not kill people randomly. Instead, the Black Death acted as a powerful force of natural selection, and this resulted in it changing one of the most important systems in the human body: the immune system. But this came with lasting trade-offs. Now evidence suggests that individuals who were already in poorer health, or whose immune systems responded less effectively, were more likely to die. That means the survivors were not just lucky—they were, in many cases, biologically better equipped to survive infection.

Because those individuals survived, they passed this variant on to their descendants. As a result, its frequency likely increased in the population during and after the pandemic. This is one of the clearest examples of natural selection acting on humans in recorded history. But like many evolutionary adaptations, this advantage came with a cost.
The same immune-related variants that may have helped people survive the Black Death are now associated with a higher risk of autoimmune diseases. Conditions like Crohn’s disease, rheumatoid arthritis, and lupus are all linked to an overactive immune system

Sources:
Spyrou, M.A., Musralina, L., Gnecchi Ruscone, G.A. et al. The source of the Black Death in fourteenth-century central Eurasia. Nature 606, 718–724 (2022). https://doi.org/10.1038/s41586-022-04...
Ancient DNA shows people with certain genes were more likely to survive the Black Death | University of Chicago News
Klunk, J., Vilgalys, T.P., Demeure, C.E. et al. Evolution of immune genes is associated with the Black Death. Nature 611, 312–319 (2022). https://doi.org/10.1038/s41586-022-05...
How Black Death survivors gave their descendants a genetic edge : Goats and Soda : NPR
How the Black Death shaped human evolution | National Institutes of Health (NIH)
How the Black Death changed our immune systems | Science | AAAS
Black Death: DNA analysis reveals source of plague | CNN
Genetic traits of Black Death survivors linked to autoimmune diseases today | Health | The Guardian
Black Death 700 years ago affects your health now - BBC News

Creative Commons Imagery:

Flappiefh File:1346-1353 spread of the Black Death in Europe map.svg - Wikimedia Commons Creative Commons Attribution-Share Alike 4.0 International license. Deed - Attribution-ShareAlike 4.0 International - Creative Commons

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