A stretch of DNA linked to Covid-19 was passed down from Neanderthals 60,000 years ago, according to a new study.
Scientists don’t yet know why this particular segment increases the risk of severe illness from the coronavirus. But the new findings, which were posted online on Friday and have not yet been published in a scientific journal, show how some clues to modern health stem from ancient history.
“This interbreeding effect that happened 60,000 years ago is still having an impact today,” said Joshua Akey, a geneticist at Princeton University who was not involved in the new study.
This piece of the genome, which spans six genes on Chromosome 3, has had a puzzling journey through human history, the study found. The variant is now common in Bangladesh, where 63 percent of people carry at least one copy. Across all of South Asia, almost one-third of people have inherited the segment.
Elsewhere, however, the segment is far less common. Only 8 percent of Europeans carry it, and just 4 percent have it in East Asia. It is almost completely absent in Africa.
It’s not clear what evolutionary pattern produced this distribution over the past 60,000 years. “That’s the $10,000 question,” said Hugo Zeberg, a geneticist at the Karolinska Institute in Sweden who was one of the authors of the new study.
One possibility is that the Neanderthal version is harmful and has been getting rarer over all. It’s also possible that the segment improved people’s health in South Asia, perhaps providing a strong immune response to viruses in the region.