A new study has identified that the stretch of DNA that may be linked to COVID-19 was passed down from the Neanderthals 60,000 years ago. However, they still do not know the reason why this particular segment increases the risk of having severe illness from the coronavirus.
The new findings posted online on Friday but have not yet been published in a scientific journal, suggest that modern health system came from ancient history.
Geneticist Joshua Akey of Princeton University said, "This interbreeding effect that happened 60,000 years ago is still having an impact today."
Stretch of DNA Linked to COVID-19
According to the study, the genome piece spans six genes on Chromosome 3 and has had a puzzling journey throughout human history. It is now common in some countries such as Bangladesh, wherein 63% of the people carry at least one; and across South Asia where almost one-third of people have inherited the segment.
But elsewhere, the segment is far less common. For instance, only 8% of Europeans carry the gene, and just 4% have it in East Asia. Meanwhile, it is almost not present in Africa.
It is not clear yet what evolutionary pattern created this distribution over the past 60,000 years. Geneticist Hugo Zeberg of the Karolinska Institute in Sweden and one of the authors in the study said that it is the $10,000 question that needs to be answered.
One explanation could be that the Neanderthal version of the segment is harmful and has been getting rarer in humans. Or it could also have improved the health of the people in South Asia, which provides a strong immune response to viruses in the region.
The researchers are only starting to understand why other people have a more severe case than others.
Neanderthal Genes Can Be Harmful but Provide an Evolutionary Edge
Genes also play a role. Just last month, researchers found that two places in the genome are associated with a higher risk. One is on Chromosome 9, which includes gene ABO that determines blood type, and the other one is on Chromosome 3, where the Neanderthal segment is found.
But genetic findings are rapidly updated as more people become infected with the virus. The new study showed an even stronger link between the disease and the Chromosome 3 segment. People who carry two copies of the segment are three times likely to suffer a severe form of the infection than those who do not have it.
Many Neanderthal genes disappeared because it has been a burden on people's health and may have made it harder to have children.
But some genes appear to have provided an evolutionary edge and became more common. It has been associated with increased fertility and fewer miscarriages in one-third of European women with the Neanderthal hormone receptor.
Furthermore, Dr.Zeberg also knew that some of the Neanderthal genes common today help humans fight viruses. He also found that the version that raises people's risk of severe COVID-19 is also found in a Neanderthal who lived 50,000 years ago.
It is possible that an immune response that worked against ancient viruses has overreacted against the novel coronavirus, and people develop a severe form of COVID-19 because their immune system launch uncontrolled attacks that scarred their lungs, which caused the inflammation.
Dr. Zeberg said that the 60,000 journey of this segment in humans might explain why it is dangerous today.