A new study has found out that the genes linked to severe coronavirus symptoms may have been passed down from Neanderthals over 60,000 years ago due to the interbreeding with modern humans, says a report in the New York Times.
According to the researchers, the interbreeding effect that happened 60,000 years ago is still having an impact today. They discovered that a particular segment of the genome that spans six genes on Chromosome 3 may be causing severe illness due to the coronavirus. The study was conducted based on data from 3,199 hospitalized COVID-19 patients and control patients.
That particular genome segment has been inherited in a puzzling manner throughout human history, says the report. Further, the study has also revealed that 63 per cent of Bangladeshis now carry at least one copy.
The genome segment of 49.4 kilobases size, however, is not found in other parts of the world as much as it is found in Asia, especially Bangladesh. Only eight per cent of Europeans and four per cent of East Asians carry it. Interestingly, this particular genome is not present in Africans.
The researchers are trying to understand why coronavirus is more dangerous for some people than others. The new data suggest that there is a stronger link between the disease and the Chromosome 3 segment. The people who carry two copies of these genes are three times more likely to suffer from severe illness than people who do not.
Chromosome 3 passed down from Neanderthals to modern humans
According to Hugo Zeberg, a geneticist at the Karolinska Institute in Sweden who is a co-author in the yet to be published study, nearly 60,000 years ago, some ancestors of modern humans settled in Europe, Asia and Australia. These people encountered Neanderthals and interbred with them. As Neanderthal DNA entered our gene pool, it spread down through the generations, long after Neanderthals became extinct.
However, Neanderthal genes turned out to be harmful to modern humans and became a burden on people’s health or made it harder to have children. As a result, due to evolution, the Neanderthal genes became rarer and began to disappear from our gene pool. But, some genes appear to have provided an evolutionary edge and have become quite common. The scientists speculate that it may have provided an improved immunity against virus in some particular regions.
In May, Dr Zeberg, and his co-authors Dr Paabo and Dr Janet Kelso from the Max Planck Institute in Leipzig, Germany, found out that at least one-third of European women have a Neanderthal hormone receptor. It is associated with increased fertility and fewer miscarriages.
When Dr Zeberg looked at Chromosome 3 in an online database of Neanderthal genomes, he discovered that the version that raises people’s risk of severe coronavirus is the same version found in a Neanderthal who lived in Croatia 50,000 years ago.
So far, research has suggested that men are more at risk than women and older people are more at risk than the young. Social conditions and even blood types are now being studied for their affect on the risk factor.
The scientists have stated that it is also possible that the genome segment from neanderthals, which had provided immunity from virus thousands of years ago, has now been triggering ‘overreactions’ against the new coronavirus.
It has been found that severe cases of COVID-19, with lungs damage and heightened inflammation are caused by an aggravated immune response in some individuals. People of Bangladeshi descent are showing a higher mortality rate due to coronavirus in the United Kingdom, the report mentioned.