A Coronavirus Epidemic Hit 20,000 Years Ago, New Study Finds

An anonymous reader quotes a report from The New York Times: Researchers have found evidence that a coronavirus epidemic swept East Asia some 20,000 years ago and was devastating enough to leave an evolutionary imprint on the DNA of people alive today. The new study suggests that an ancient coronavirus plagued the region for many years, researchers say. The finding could have dire implications for the Covid-19 pandemic if it's not brought under control soon through vaccination. 'It should make us worry,' said David Enard, an evolutionary biologist at the University of Arizona who led the study, which was published on Thursday in the journal Current Biology. 'What is going on right now might be going on for generations and generations.'

Over generations, viruses drive enormous amounts of change in the human genome. A mutation that protects against a viral infection may well mean the difference between life and death, and it will be passed down to offspring. A lifesaving mutation, for example, might allow people to chop apart a virus's proteins. But viruses can evolve, too. Their proteins can change shape to overcome a host's defenses. And those changes might spur the host to evolve even more counteroffensives, leading to more mutations. When a random new mutation happens to provide resistance to a virus, it can swiftly become more common from one generation to the next. And other versions of that gene, in turn, become rarer. So if one version of a gene dominates all others in large groups of people, scientists know that is most likely a signature of rapid evolution in the past.

In recent years, Dr. Enard and his colleagues have searched the human genome for these patterns of genetic variation in order to reconstruct the history of an array of viruses. When the pandemic struck, he wondered whether ancient coronaviruses had left a distinctive mark of their own. He and his colleagues compared the DNA of thousands of people across 26 different populations around the world, looking at a combination of genes known to be crucial for coronaviruses but not other kinds of pathogens. In East Asian populations, the scientists found that 42 of these genes had a dominant version. That was a strong signal that people in East Asia had adapted to an ancient coronavirus. But whatever happened in East Asia seemed to have been limited to that region. The scientists then tried to estimate how long ago East Asians had adapted to a coronavirus. They took advantage of the fact that once a dominant version of a gene starts being passed down through the generations, it can gain harmless random mutations. As more time passes, more of those mutations accumulate. Dr. Enard and his colleagues found that the 42 genes all had about the same number of mutations. That meant that they had all rapidly evolved at about the same time. 'This is a signal we should absolutely not expect by chance,' Dr. Enard said. They estimated that all of those genes evolved their antiviral mutations sometime between 20,000 and 25,000 years ago, most likely over the course of a few centuries. It's a surprising finding, since East Asians at the time were not living in dense communities but instead formed small bands of hunter-gatherers.

Read more of this story at Slashdot.