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The genetic legacy of Neanderthals, a factor that could be crucial against COVID-19

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A group of researchers has been studying the inheritance of men who lived on Earth 60,000 years ago for months. Their findings could explain why the disease affects more or less the populations of some countries

New studies appear to have uncovered the links between the way COVID-19 manifests itself and the presence of inherited Neanderthal genetics.

To the extent that almost half of the Neanderthal genome still survives, scattered in small amounts among almost all the DNA in today’s population – with the exception of Africans, since it appears that Neanderthals never lived on the continent – those genes are they have associated with everything from hairiness to fat metabolism.

Many seem to be related to the immune system and to be decisive before the risk of developing diseases such as lupus, Crohn’s disease, diabetes and, scientists say, Covid-19 also belongs to that list. Two long sections of DNA, both inherited from Neanderthals, appear to confer resistance or susceptibility to severe COVID-19, depending on which is present.

The investigations were led by scientists Svante Pääbo and Hugo Zeberg in the German city of Leipzig, both pioneers in the study of Neanderthal DNA.

Their first paper, published in Nature in September, described a Neanderthal DNA strand, known as a “haplotype,” that is associated with an increased risk of severe disease. Having a copy of the haplotype, which is found on the third of the 46 chromosomes that humans possess, doubles the chances of ending up in intensive care. Those who are unlucky enough to own two copies, one from each parent, face an even greater risk.

But that genetic bad luck is not evenly distributed. The genetic sequence is most common among people of South Asian descent, with 63% of the Bangladeshi population carrying at least one copy; and among Europeans, where the prevalence is around 16%. As expected, it is practically absent from Africa. Surprisingly, it is also very rare in large areas of East Asia.

The second study, published this week in the Proceedings of the National Academy of Sciences, refers to another Neanderthal haplotype, which is found on chromosome 12. Its effect is protective, although it is also less powerful: having a single copy is associated with a 22% less chance of critical illness.

This helpful sequence is more common than the harmful one. It is present in all parts of the world except sub-Saharan Africa. Between 25% and 35% of the Eurasian population carries at least one copy. In Vietnam and eastern China, more than half the population is a carrier. It also exists, at much lower rates, among American populations of primarily African descent, many of whom will also have more recent Eurasian ancestry.

The haplotype hinders the spread of RNA viruses, of which SARS-COV-2 is one, by causing cells infected with them to rapidly self-destruct. It is known to provide at least some protection against the West Nile virus, hepatitis C, and interestingly SARS-COV-2, which caused the SARS outbreak that began in 2002.

“Certainly there are other factors, such as advanced age or underlying conditions such as diabetes that have a major impact on the development of the disease,” said Professor Pääbo, from the OIST Evolutionary Genomics Unit. “But genetic factors also play an important role and some of them have been contributed by Neanderthals.”

The researchers hope their work will help clarify why some countries, and some populations within those countries, appear to have been more affected by COVID-19 than others. They note, for example, that British people of Bangladeshi descent suffer from severe COVID-19 at roughly twice the rate of the general population.

If COVID-19 becomes an endemic disease, as seems likely, gene sequencing may, in the future, help clinicians assess which patients are likely to be vulnerable to its worst effects. Understanding the mechanisms by which genes confer resistance or susceptibility can help in the search for drugs. And history suggests that sars-cov-2 is unlikely to be the latest novel coronavirus to make the leap from animals to humans.

According to scientists, Neanderthals became extinct about 40,000 years ago, although they did not disappear from Earth completely. In the last decade it has become clear that Neanderthals mated with the ancestors of modern humans, and that at least some of those unions produced viable offspring. The result is that almost half of the Neanderthal genome still survives, scattered in small amounts throughout most of the DNA of modern people.

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