‘Viking’s Disease’ Hand Condition Traced Back to Ancestral Neanderthals
Researchers have discovered a link between Neanderthal genetic material and an unusual health disorder that affects modern humans. The disorder in question is Dupuytren’s disease, a.k.a. Viking’s disease, a hand condition that can cause some of a person’s fingers to become permanently bent at an angle.
Neanderthals living 40,000 to 50,000 years ago undoubtedly suffered from some form of this condition. Through genetic mixing they passed this vulnerability on to humans living alongside them in Northern Europe.
As explained in a new paper just published in Molecular Biology and Evolution, Dupuytren’s disease is far more common in people of Northern European descent than in those whose predecessors came from Africa. In fact, the name “Viking disease” comes from its predominance among descendants of the ancient Viking warriors who once ruled Scandinavia.
Highlighting the latter relationship, one study found that about 30 percent of Norwegians above the age of 60 experience the symptoms of Dupuytren’s disease, usually in their middle and/or ring fingers. “This is a case where the meeting with Neanderthals has affected who suffers from illness,” said the paper’s lead author, evolutionary geneticist Hugo Zeberg from the Karolinska Institute in Solna, Sweden. Nonetheless, he emphasized that it is important not to overstate the connection between Vikings and Neanderthals.
Representational image of Viking male suffering from Viking’s disease, also known as Dupuytren’s disease. (Krakenimages.com / Adobe Stock)
Viking’s Disease: Then and Now
It was in Europe that much of the interbreeding between Neanderthals and modern humans occurred between 42,000 and 65,000 years ago. African populations lived separately from Neanderthals, who occupied Eurasia exclusively. As a result, people of African descent only possess traces of Neanderthal DNA today.
In 1999, a Danish study of twins determined that the development of Dupuytren’s disease is most heavily influenced by heredity, with its heritability factor estimated to be at 80 percent. While other risk factors for the condition have been identified, including age, alcohol use and diabetes, a genetic predisposition must always be present.
This means that Neanderthal genetic material absorbed into the human genome is, in a very real sense, the true cause of this condition. It was the prevalence of Dupuytren’s disease among Northern Europeans in particular that intrigued the scientists enough to motivate their study of the condition’s genetic origins.
A ring finger locked in a bent position as seen in Dupuytren's disease, colloquially known as “Viking’s disease.” (Hugo Zeberg / Molecular Biology and Evolution)
To facilitate their research, the team of experts led by Hugo Zeberg analyzed data collected from 7,871 people with the disorder and 645,880 control subjects listed in the UK Biobank, the FinnGen R7 collection and the Michigan Genomics Initiative. Their purpose was to identify the presence of genetic variants that could be connected to Dupuytren’s disease.
Through extensive comparative analysis, scientists identified 61 genetic variants associated with Viking’s disease, with three of them known to originate from Neanderthals. Most significantly, the second and third most strongly associated variants came from the Neanderthals, suggesting that these extinct human cousins were particularly susceptible to Dupuytren’s disease.
The scientists taking part in the study believe that the widespread prevalence of this condition in present-day human populations would be highly unlikely without there having been contact and interbreeding with Neanderthal populations.
Contrary to popular belief, researchers have confirmed that Neanderthals and Homo sapiens interbred, leading to many humans today possessing genetic material inherited from their Neanderthal ancestors. (Rawf8 / Adobe Stock)
Neanderthal DNA: A Curse, a Blessing, or a Mixture of Both?
Studies have shown that about two percent of the human genome is comprised of DNA sourced from distant Neanderthal ancestors. Only trace amounts are found in those who are descended from people who lived in sub-Saharan Africa, based on the lack of Neanderthal penetration into that part of the world.
While it might not sound like all that much, human development has been significantly impacted by the presence of this genetic material. The study linking so-called Viking’s disease to Neanderthal genes is not particularly surprising, because other studies have found a clear connection between our Neanderthal generic inheritance and various human health conditions.
For example, comprehensive research published in 2014 found links between Neanderthal genes and type 2 diabetes, Crohn’s disease, biliary cirrhosis (an autoimmune disease of the liver) and incidence of depression. Recent studies have even suggested a link between Neanderthal genes and susceptibility to Covid-19.
These genes didn’t necessarily introduce new types of ill health to the human gene pool. But they did increase the likelihood of certain disorders developing. Further research may indicate that other human health conditions are affected by Neanderthal DNA in the same way.
For the most part, Neanderthal genes are concentrated in areas that code for the creation of human skin and hair. Scientists believe this DNA was picked up and passed on because it had survival advantages: Neanderthal contributions would have given humans the ability to grow thicker hair and skin, which would have helped protect them from the colder climates they encountered in Eurasia once they’d left the African continent.
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Given the assumptions behind this theory, the persistence of Neanderthal genes that increase disease risk seems surprising, since this DNA would reduce survival chances rather than increasing them. It’s possible that Neanderthal genes have survived in humans as a result of random chance, offering benefits in some cases and increasing vulnerability in others.
What all the research shows conclusively is that Neanderthal genes do have a significant impact on human health and development. In the context of Viking's disease, Neanderthals introduced a genetic condition to the human gene pool that is unpleasant but does not pose a significant threat to survival. The majority of individuals affected by this disorder were likely unaware of their Neanderthal genetic heritage until now. However, with this recent scientific revelation, it is probable that they will never forget their newfound ancestral Neanderthal connection.
Top image: The hand of a person with Viking’s disease, a.k.a. Dupuytren’s contracture, a condition of the hand that can cause some of a person’s fingers to become permanently bent at an angle. Source: Artwell / Adobe Stock
By Nathan Falde