A gene passed down from Neanderthal ancestors could play a part in how their descendants respond to Covid-19, a study published on Tuesday found.
The gene variant that increases the risk of becoming seriously ill with Covid also reduces the risk of contracting HIV by 27 per cent, researchers in Germany and Sweden found.
During the coronavirus pandemic, people from South Asia were found to have been at greater risk of catching the virus than other groups.
The mutated genes inherited from Neanderthals doubled the risk of severe Covid-19, Dr Hugo Zeberg, of the Max Planck Institute for Evolutionary Anthropology in Germany, found.
About 50 per cent of South Asians carry the mutation compared to one-fifth of Europeans.
“This major genetic risk factor for Covid-19 is so common that I started wondering whether it might actually be good for something, such as providing protection against another infectious disease”, Dr Zeberg said.
“We don't know at the moment why it was likely advantageous 10,000 years ago. There are many genes involved in the immune system in this region of the genome, so there are many plausible candidate genes.
“If I were to guess, smallpox would be a good candidate. It also enters cells using chemokine receptors. But at this point, this is just speculation.”
In the spring 2021, the team found the frequency of the Neanderthal variant had increased significantly since the last ice age, and it had become an unexpectedly common.
That hints that it may have a benefit, which inspired the team to continue research.
By analysing patient data, they found that carriers of the risk variant for Covid had a 27 per cent lower risk of contracting HIV.
“This shows how a genetic variant can be both good and bad news: Bad news if a person contracts Covid-19, good news because it offers protection against getting infected with HIV”, Dr Zeberg said.