A study of DNA taken from victims of the Black Death and other survivors in medieval Europe shows that the massive plague continues to have an impact on our biology today.
It is not only because of the pathogen Is still activeBut, because the deadly, widespread pandemicThis triggered adaptations in the immune system, which remained active for hundreds of decades.
These changes may not be for our long-term good. Scientists have discovered that the same genes that confer resistance to the plague may also be linked to increased susceptibility to autoimmune diseases like Crohn’s disease or rheumatoid.
This finding suggests that pandemics could have unexpected and sometimes harmful long-term effects that can ripple down through generations.
The Black Death was a devastating event that swept across Europe and Asia in the middle to the mid-1700s. It claimed the lives of tens to hundreds millions of people in Europe, Asia, Africa. It was caused in part by the Yersinia pestisA bacterium that is transmitted to humans by fleas can cause a deadly disease. Death in less than a Day.
These infectious diseases are one of the most powerful pressures on natural selection. Particularly for people. Consider sickle cell anemia, which is a genetic condition that can also offer a certain degree of remission. Resistance against more dangerous malaria. A person with sickle cell is more likely than someone without it to survive. malariaThey’ll also be able to have more children with sickle cell anemia. The incidence of sickle cells anemia increases over time in populations who live in malaria-prone areas.
A team of international scientists, led by Jennifer Klunk of McMaster University Canada and Tauras Vigalys of University of Chicago, wanted to determine if the Black Plague had affected the human genome.
“When a pandemic of this nature – killing 30 to 50 per cent of the population – occurs, there is bound to be selection for protective alleles in humans, which is to say people susceptible to the circulating pathogen will succumb,” Hendrik Poinar, evolutionary geneticist, explainsMcMaster University
“Even a small advantage can make the difference between survival and death.” Survivors who are still in their reproductive years will inherit their genes.
Researchers today have a lot to study because the Black Plague was so prevalent and many people were buried in mass graves. Scientists focused their attention on the 100-year period before, during and after the Black Plague. They collected over 500 samples from victims of the Black Plague in London and Denmark. These samples represented three categories: people who died before the plague (retrieved form a London mass grave), people who died during and those who survived.
Researchers were able to find four genes associated with the Black Death by comparing their genomes. This was a feat that has never been achieved before in human history. These genes produce proteins that protect our bodies against pathogens. Individuals with one or more of the variants were more likely than others to survive the plague.
In order to confirm what the ancient DNA implied, researchers created cultures from human cells that represented different genetic profiles and infected them. Yersinia pestis. They found that the genes they had previously studied were present in the most resistant cultures to the bacterium.
Particularly, those who had two identical copies of ERAP2 gene were approximately 40 to 50 percent more likely than those with the other copies to survive the plague. These genes seem to have conferred an increased susceptibility.
“The selective advantages associated with the chosen loci are amongst the strongest ever reported by humans and show how a single pathogen could have such an effect on the evolution the immune system,” says geneticist Luis BarreiroUniversity of Chicago
As time passed, the effects of the plague decreased and the human race moved on. There was one problem. Researchers discovered that some gene variants are associated with increased susceptibility for autoimmune diseases. Since the plague would have been the bigger evolutionary pressure back in the 1340s – like malaria and sickle cell anemia – this result was probably unavoidable.
The researchers believe this evidence provides empirical support for an association between autoimmune risks and adaptation to an infection that has been around for centuries.
Understanding the dynamics of the immune system is crucial to understand how past pandemics like the plague have contributed to modern disease susceptibility. Poinar says.
The results of the research by the team have been published in Nature.
