If your hand has this spot, you may have the blood of another species.

A new study led by the 2022 Nobel Prize winner in Medicine finds that the "Viking disease" is actually a legacy of our ancestors' interbreeding with other species, Neanderthals.

'Viking disease' is a rare condition in which older men have several fingers stuck in a bent position . Because the condition is most common in northern Europe – affecting 30% of men over the age of 60 – it is known as Viking disease (after the Vikings who lived in northern Europe).

According to SciTech Daily, a group of scientists from the Karolinska Institute (Sweden), led by Associate Professor Hugo Zeberg and Professor Svante Pääbo, analyzed the genetic data of more than 7,800 people with Viking disease and found a surprising factor: Traces of other species .

A few bent fingers may be due to an underlying gene variant inherited from our ancestors other than the Neanderthals - (Photo: KAROLINSKA INSTITUTE)

Viking disease, officially called Dupuytren's contracture , can affect women, but most patients are men. It usually starts with a lump in the palm of the hand that grows larger and causes one or more fingers to bend.

"Because Dupuytren's contracture is rare in people of African descent, we wondered whether Neanderthal gene variants might partly explain why," explains Professor Zeberg.

Neanderthals were a different species from the genus Homo, along with our modern Homo sapiens (also known as Homo Sapiens), as well as the Denisovans, Homo Erectus.

Homo sapiens groups that left Africa tens of thousands of years ago met and lived with many other human communities such as Neanderthals and Denisovans, giving rise to intermarriage. Therefore, Africans are the most "pure" Homo sapiens population, becoming an important control in the study of heterogeneous genetic factors in humans.

According to the study, the 7,800 people mentioned above belong to 3 groups of patients in the US, UK and Finland.

The team then compared the data collected from these patients with the genomes of 645,800 other healthy people, screening for 61 genetic risks that could be linked to Viking disease.

From there, they screened further and discovered three genetic traits that were indeed the legacy of the Neanderthal ancestors, including two factors that played the second and third most important roles in the disease.

The discovery helps complete an increasingly complete picture of how genes from other human species influence modern humans. It's not always a negative effect. Neanderthal genes also help many people reproduce more easily, avoid certain infectious diseases, have better metabolisms, etc.

One of the study's two lead authors - geneticist Svante Pääbo - is the 2022 Nobel Prize winner in Medicine for his discoveries related to Neanderthals, including the successful sequencing of their genome.