According to a study published in 2021 in the journal Nature, a genetic variant inherited from the Neanderthals – an ancient population of hominids that lived in Eurasia between 200,000 and 35,000 years ago – may have increased the risk factors for developing severe Covid-19 for a significant number of the world’s population.
A modification in the gene called LZTFL1 – which is believed to act on lung cells – seems to have a significant role in boosting the production of a lung surface protein which the coronavirus uses to latch onto and spread to the lungs, leading to pneumonia and sometimes even death. Nowadays, this genetic quirk seems to be more common in people of south Asian origin, a feature which could partially explain the high death toll in India during the devastating Delta wave in 2021.
Now, James Davies, a professor of Genomics at the University of Oxford and one of the experts that identified this gene, has argued at the Cheltenham Science Festival that this mutation has probably emerged from a single “romantic liaison” between a Neanderthal and a member of our species about 60,000 years ago.
“If you stop and think about it, this comes from a single interspecies relationship and a single child. And if the dinner date between the human and the Neanderthal had gone wrong, we would have had a much better time in Covid, and had hundreds of thousands fewer deaths,” Professor Davies explained.
Since the average Neanderthal group size is estimated to have been about 20 to 25 individuals, the chances of Neanderthals bumping into each other, let alone Homo sapiens, were probably very low, making the sexual encounter that introduced the Covid-related gene into modern humans a remarkable event. Moreover, genetic analyses which found that many people with high-risk of severe Covid have exactly the same 28 differences in the “letters” making up their genetic code suggest that they all descended from the same two people, rather than from a variety of interbreeding Neanderthals and Homo sapiens.
“We think it’s a single romantic liaison, and the reason we know that is that it’s inherited as this block with 28 single-letter changes, and you can track that all the way back and it has to be a single event,” explained Professor Davies. Asked for a rough estimate of how many people may have died of Covid as a result of this single, 60,000-year-old interspecies sexual encounter, Davies provided a rather grim figure: “It’s in the hundreds of thousands to a million.”
“I want you to keep in mind, when we start thinking about the time when Neanderthals and Homo sapiens bumped into each other and went on that dinner date, just how far back in time this was, and 60,000-odd years later, we are seeing the impact of that encounter in the world today in more severe forms of Covid,” concluded Simon Underdown, a professor of Biological Anthropology at Oxford Brookes University.