A stretch of DNA, thought to triple the risk of developing severe COVID-19, has been passed down by Neanderthals to modern humans, scientists claim.
The group of genes, found on chromosome three, was linked to a higher risk of hospitalisation and respiratory failure after infection with the SARS-CoV-2, the virus which causes COVID-19. Researchers based at the Karolinska Institute in Sweden and the Max Planck Institute for Evolutionary Anthropology in Germany have now identified the origins of the gene cluster by comparing its DNA sequence with that of our extinct human ancestors.
'I almost fell off my chair because the segment of DNA was exactly the same as in the Neanderthal genome,' Professor Hugo Zeberg, co-lead author on the study, told the Guardian. The last common ancestor between the groups lived 550,000 years ago, during which time the genetic variant would have almost certainly been altered. Therefore, it is more likely that the 'variant was inherited by modern humans from the Neanderthals when they interbred some 60,000 years ago' he explained.
It remains unclear how these genes may cause worsened COVID-19 symptoms, but one is known to play a role in the immune response and another has been linked to how the virus invades human cells. The authors suspect these genes persisted in modern humans because they were once beneficial, perhaps helping to fight off ancient viruses. 'Now, when we are faced with the novel coronavirus, these Neanderthal genes have tragic consequences' said Professor Svante Pääbo, director of the Max-Planck Institute for Evolutionary Anthropology and co-lead author on the study.
The study, first reported in July (see BioNews 1155), now published in Nature, also revealed differences in the prevalence of this variant across the globe, with roughly 50 percent of people in South Asia carrying the risk variant, only 16 percent in Europe and almost no carriers in Africa and East Asia. The variant was most commonly found in people from Bangladesh (63 percent), which may explain why people of Bangladeshi descent in the UK are twice as likely to die from COVID-19 than the general population.
However, Professor Mark Maslin, a professor at University College London and author of the book 'The Cradle of Humanity', cautioned that their work risks oversimplifying the causes and impact of the pandemic. 'COVID-19 is a complex disease', which is 'influenced by many environmental, health and genetic factors', he said. 'As COVID-19 spreads around the world it is clear that lots of different populations are being severely affected, many of which do not have any Neanderthal genes.' he added.
The authors, too, emphasise there are many other elements involved. 'Obviously, factors such as your age and other diseases you may have also affect how severely you are affected by the virus' said Professor Zeberg, 'but among genetic factors, this is the strongest one.'