The devastation caused by the Black Death left such a profound genetic imprint on humans that it continues to harm our health nearly 700 years later. In the mid-1300s, when the Black Death swept across Europe, up to half of the population perished.
A groundbreaking analysis of the DNA of ancient skeletons revealed abnormalities that let plague survivors survive. However, these mutations are linked to auto-immune disorders that currently affect humans. The Black Death is one of human history’s most momentous, lethal, and miserable events. According to estimates, up to 200 million people perished.
As per BBC, researchers hypothesized that an event of such magnitude must have influenced human evolution. They could precisely date the human remains to before, during, or after the Black Death by analyzing DNA extracted from the teeth of 206 old skeletons.
Bones from London’s East Smithfield plague trenches, used for mass graves, were analyzed with additional samples from Denmark. The remarkable finding, published in the journal Nature, concerned alterations in the ERAP2 gene.
If you had the proper mutations, you had a 40% greater chance of surviving the disease. Professor Luis Barreiro from the University of Chicago told me, “That’s huge, it’s a huge influence, and it’s surprising to find anything like that in the human DNA.”
The gene’s function is to produce the proteins that fragment are invading germs and present the fragments to the immune system, so preparing it to recognize and destroy the enemy more efficiently.
You inherit a copy of the gene from each parent, which is available in both functional and inactive forms. Consequently, those who were most likely to survive got a version with optimal functionality from their parents. And as a result of the survivors having children and passing on these advantageous mutations, they grew exponentially more prevalent.
Professor Hendrik Poinar, an evolutionary geneticist at McMaster University, told me, “It’s enormous that we detect a 10% shift over two to three generations; it’s the strongest selection event in humans to date.”
Modern investigations employing the plague bacterium Yersinia pestis verified the results. Blood samples from individuals with advantageous mutations were more resistant to infection than those from those without. Prof. Poinar remarked, “It’s like watching the Black Death emerge in a petri dish; that’s eye-opening.”
Even now, these mutations are more prevalent than they were before the Black Death. The issue is that they have been connected to auto-immune disorders such as the inflammatory bowel disease Crohn’s – something that kept your ancestors alive 700 years ago but may be detrimental to your health now.
Other historical influences on our DNA have a lasting effect on us. Around 1% to 4% of present human DNA is a result of our ancestors’ mating with Neanderthals, and this inheritance impacts our resistance to diseases such as Covid. “These wounds from the past continue to have a tremendous effect on our susceptibility to disease now,” stated Professor Barreiro.
Prof. Barreiro stated that the 40% survival advantage represented the “strongest selected fitness effect yet assessed in humans.” It dwarfs the benefits of HIV-resistance variants and milk digestion modifications, but he cautions that precise comparisons are difficult.
However, the Covid epidemic will not leave a comparable legacy. Your ability to reproduce and pass on your genes drives evolution. Covid kills the elderly who have already passed their childbearing years. Plague’s capacity to kill people of all ages and in such large numbers contributed to its enduring influence.
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