It may have once helped our ancestors fight off other forms of infections - but scientists have now claimed that a strand of DNA passed down from Neanderthals to modern humans could be a major risk factor for contracting severe forms of COVID-19. 

Neanderthal DNA could be a coronavirus risk factor

Possessing Neanderthal genes could increase the chances of suffering from a severe coronavirus infection, according to a new study published by the Max Planck Institute in Germany. The DNA strand, which researchers claim triples the risk of developing severe COVID-19, is a genetic hand-me-down from approximately 60.000 years ago, when Neanderthals and modern humans interbred. 

In the study, published this week in the journal Nature, researchers estimate that around 16 percent of Europeans and half of south Asians still carry these genes today. The gene cluster is most commonly found in Bangladesh, where 63 percent of the population carry at least one copy of the sequence. In Africa and East Asia, on the other hand, it is virtually non-existent. 

The origins of the risk genes were discovered when scientists in Germany and Sweden compared the DNA of seriously ill coronavirus patients with those from Neanderthals and Denisovans. They found that the DNA sequence that makes patients more likely to fall seriously ill was very similar to samples collected from a 50.000-year-old Neanderthal from Croatia. 

“The probability that humans who inherited this gene variation have to be put on a ventilator when they contract the novel coronavirus Sars-CoV-2 is three times higher,” said Hugo Zeberg, an evolutionary anthropologist at the Karolinska Institute in Stockholm. It is also linked with a higher risk of hospitalisation and respiratory failure - making the risk associated with the gene cluster similar to other coronavirus risk factors like age or pre-existing conditions. 

Genes may have once provided protection against other diseases

How exactly the genes may worsen COVID-19 is still unclear, but researchers suggest that one gene plays a role in the immune response, while another has been linked to the way the virus invades human cells. “We are trying to pinpoint which gene is the key player, or if there are several key players, but the honest answer is that we don’t know which are critical in COVID-19,” said Zeberg.

Zeberg and his co-author, Svante Pääbo, director of the Max Planck Institute of Evolutionary Anthropology in Leipzig, hypothesise that modern humans have retained the Neanderthal genes because they once provided protection against other types of infection. It’s only now that their downside is being exposed.

“The genes in this region may well have protected the Neanderthal against some other infections that are not around today,” said Pääbo. “And now, when we are faced with the novel coronavirus, these Neanderthal genes have these tragic consequences.”