How Black Death Survivors Gave Their Descendants An Edge During Pandemics: NPR

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Last edited Thu Oct 20, 2022, 11:11 PM - Edit history (1)

- NPR, October 19, 2022. - When the bubonic plague arrived in London in 1348, the disease devastated the city. So many people died, so quickly, that the city's cemeteries filled up. - Ed.

"So the king [Edward III], at the time, bought this piece of land and started digging it," says geneticist Luis Barreiro at the University of Chicago. This cemetery, called East Smithfield, became a mass grave, where more than 700 people were buried together. "There's basically layers and layers of bodies one on top of each other," he says. The city shut down the cemetery when the outbreak ended. In the end, this bubonic plague, known as the Black Death, likely killed 30 to 50% of people in parts of Europe and the United Kingdom.

That's a mortality rate that's at least 200 times higher than the one estimated for COVID, Barreiro points out.

"We all think that COVID-19 was insane and completely changed the world and our societies," Barreiro says. "COVID has a mortality rate of about 0.05% – something like that. Now try to project – if it's even possible – a scenario where 30 to 50% of the population dies." Now a new study, published Wednesday in the journal Nature, shows that the Black Death altered more than society: It also likely altered the evolution of the European people's genome.

In the study, he and his colleagues found that Black Death survivors in London and Denmark had an edge in their genes – mutations that helped protect against the plague pathogen, Yersinia pestis. Survivors passed those mutations onto their descendants, and many Europeans still carry those mutations today. But that edge comes at a cost: It increases a person's risk of autoimmune diseases. "The exact same genetic variant that we find to be protective against Yersinia pestis is associated with an increased risk for Crohn's disease today," Barreiro says.

The study demonstrates how past pandemics could prepare the human immune system to survive future pandemics."The evolution is faster and stronger than anything we've seen before in the human genome," says evolutionary biologist David Enard at the Univ. of Arizona, who wasn't involved in the study. "It's really a big deal. It shows what's possible [for humans], in terms of adaptation in response to many different pathogens." In the study, Barreiro & his team set out to answer a simple question: Did the Londoners, who survived the Black Death, carry a mutation – or even mutations – in their genome that protected them from the disease?

But to answer that question, they had to do something that almost sounds like wizardry: They had to extract DNA from people who died of the plague 700 years ago...

- Read More, https://www.npr.org/sections/goatsandsoda/2022/10/19/1129965424/how-black-death-survivors-gave-their-descendants-an-edge-during-pandemics