Whoever said that history tends to repeat itself couldn’t be more right. Pandemics aren’t new to us; we’ve seen them before. But what are the odds that our ancient ancestors went through something similar to what we’re going through right now with the Covid19 pandemic?
Apparently, it’s quite possible!
A group of researchers from the University of Arizona and the Australian Centre for Ancient DNA (ACAD) conducted a study that led to the discovery of a coronavirus epidemic outbreak in the East Asia region that occurred ~20,000 years ago, leaving traces in the DNA of modern humans from that region.
“We found traces of humanity’s age-old arms race with coronaviruses written in our DNA,” Yassine Souilmi, one of the co-authors of the study, wrote in an article he published in collaboration with The Conversation.
But what does this mean for us, modern humans?
Background: Dawn of the … Undead?
Viruses are tiny, simple creatures who aren’t alive (no cells, no way to turn food into energy) and aren’t necessarily dead. Their only objective is to reproduce and, for that, they need hosts. When invading, they interact with specific proteins produced by the host cells, called viral interacting proteins (VIPs).
They’re responsible for many of the pandemics we’ve seen throughout history, which may be too many to count by now. “In the 20th century alone, three variants of the influenza virus each resulted in wide-ranging outbreaks that killed millions: the ‘Spanish Flu’ of 1918-20, the ‘Asian Flu’ of 1957-58, and the ‘Hong Kong Flu’ of 1968-69”, Souilmi wrote.
These types of major health-related events usually lead to great population adaptations that might result in resistance to infection or reduced symptoms. In current times, geneticists have created tools that allow them to look for traces in our genes that demonstrate historical adaptation events.
“Our team was curious to see whether historical encounters with ancient coronaviruses have left any such trace in today’s human populations,” reads Souilmi’s article.
Analysis: Has There Been A CoronaVirus Epidemic Before?
To understand if any major coronavirus outbreak took place in ancient history, the research team collected DNA samples from thousands of people across 26 populations and analyzed 420 genes that encode VIPs that specifically interact with coronaviruses (CoV-VIPs) to try and find traces that indicate adaptation. 42 of those genes showed strong adaptation signals, and all of them were found in East Asian populations.
“These independent lines of evidence support an ancient coronavirus (or a similarly interacting virus) epidemic that emerged in the ancestors of contemporary East Asian populations,” the scientific paper reads.
The 42 CoV-VIPs had accumulated about the same number of mutations, meaning that they rapidly evolved simultaneously, under the pressure of a big selective event. By estimating when those mutations occurred, the researchers inferred that a coronavirus outbreak took place sometime between 20,000 and 25,000 years ago in East Asia.
Souilmi also reveals that “the 42 VIPs are primarily expressed in the lungs, which is the tissue most affected by COVID-19 symptoms,” he adds that “these VIPs interact directly with the SARS-CoV-2 virus responsible for the current pandemic”.
Outlook: What can yesterday tell us about tomorrow?
This study shows that, during the epidemic, some genes involved in viral interactions were positively selected, which may have resulted in increased resistance and reduced disease severity. “Our results show how the hunt for genetic traces of historical viral outbreaks may help us treat the outbreaks of the future,” Souilmi says.
But how?
“Evolutionary genomics analyses have identified several new candidate genes that might provide novel drug targets,” the paper reads. Suppose particular mutations in VIP genes are responsible for ameliorating the effects of coronavirus infection. In that case, they can be targeted in drug treatment studies that might still be useful to us today, as we’re still fighting this pandemic.
“By revealing the identity of our ancient pathogenic foes, evolutionary genomic methods may ultimately improve our ability to predict—and thus prevent—the epidemics of the future,” the authors conclude.