Coronavirus patients who carry a peculiar gene cluster – inherited from our Neanderthal cousins – have three times the risk of ending up in a mechanical ventilator in hospital.

We already know that being aged over 60, having underlying medical conditions such as diabetes, heart disease, respiratory disease or hypertension, or being obese, are all high risk factors for developing a severe case of COVID-19.

Now, according to new research, this Neanderthal link – carried by 50 per cent of people in south Asia, and 16 per cent of Europeans – “is the major genetic risk factor” for developing respiratory failure after being infected by the coronavirus.

Professor Hugo Zeberg, researcher at the Max Planck Institute for Evolutionary Anthropology, and author of the new paper.

Modern humans, homo sapiens, acquired this gene cluster through interbreeding with Neanderthals, when the two species met about 60,000 years ago.

“Obviously, factors such as your age and other diseases you may have also affect how severely you are affected by the virus. But among genetic factors, this is the strongest one,” said Professor Hugo Zeberg, researcher at the Max Planck Institute for Evolutionary Anthropology and first author of the study.

How as this discovery made?

You probably learnt in school that all of our genetic material or DNA is contained in 23 pairs of chromosome structures that look a little like wings that are found in the nucleii of all our cells.

One chromosome in each pair inherited from each of our parents.

As researchers point out, “the vast majority are the same between people, mutations do occur, and variations persist, at the DNA level”.

The researchers looked at the genetic make-up of more than 3000 COVID-19 patients, one group that was hospitalised with severe symptoms, the other group who were infected by the virus but weren’t hospitalised.

They discovered a region on chromosome 3 that contained a cluster of variants that “influences whether a person infected with the virus will become severely ill and needs to be hospitalised”.

So where did they come from?

According to the researchers, variants like these have previously been found in Neanderthals and Denisovans. Did the modern version of these variants originate from either of these early human species?

Firstly, they found that a Neanderthal from southern Europe carried an almost identical genetic region whereas two Neanderthals from southern Siberia and a Denisovan did not.

Professor Svante Pääbo specialises in the field of evolutionary genetics.

The next question was: Did these originate in Neanderthals or were they inherited by both Neanderthals and modern humans from our most recent common ancestor – of late that’s thought to be a mysterious species named Homo antecessor.

The researchers say that if “the variants had come from the last common ancestor, they would have been around in modern humans for about 550,000 years”.

But because the variants between “the Neanderthal from southern Europe and present-day people are so similar over such a long stretch of DNA, the researchers showed that it was much more likely that they came from interbreeding”.

And this would have occurred about 60,000 years ago.

So why is the variant linked to severe COVID-19?

The short answer: The researchers don’t know. One idea is that this particular cluster of genes made Neanderthals vulnerable to illness.

Professor Svante Pääbo, director, the Max Planck Institute for Evolutionary Anthropology, in a prepared statement said: “It is striking that the genetic heritage from the Neanderthals has such tragic consequences during the current pandemic.

“This is something that we and others are now investigating as quickly as possible.”

We’ll keep you posted.