In a groundbreaking study using ancient DNA, scientists have identified why individuals of northern European descent have a higher risk of developing multiple sclerosis (MS) compared to other ancestries. The research reveals that this genetic predisposition stems from the Yamnaya, a Bronze Age people who migrated into northwestern Europe around 5,000 years ago.

The study, led by researchers from the University of Cambridge and the University of Copenhagen, involved comparing DNA samples from modern individuals with those extracted from ancient human remains. By examining the genetic profiles of the Yamnaya, who originated from the steppes of present-day Ukraine and Russia, the researchers discovered that these individuals carried gene variants associated with an increased risk of MS.

Contrary to expectations, these genetic variations proved advantageous for the Yamnaya population, allowing them to thrive and spread the genes throughout the region. Besides potentially contributing to enhanced immunity against infections carried by their livestock, the researchers suggest that the gene variants may have inadvertently triggered an autoimmune response related to MS.

The findings, published in the journal Nature, are among the many discoveries from an unprecedented gene bank containing thousands of early human samples from Europe and western Asia. The project aims to shed light on significant population migrations and the presence of disease-related genes.

MS is a complex neurological disease that can affect any population, but it is most commonly observed in individuals of northern European descent. Previous studies have struggled to explain this geographical distribution. However, the distinct genetic variants carried by the Yamnaya offer valuable insights into this phenomenon.

The researchers examined DNA from approximately 1,600 ancient Eurasian individuals, revealing important population shifts in northern Europe's history. The arrival of Middle Eastern farmers partially displaced hunter-gatherers, followed by the migration of the Yamnaya, who brought with them their herding lifestyle and the associated gene variants.

To confirm the link between the Yamnaya migration and the prevalence of MS, the research team compared the ancient DNA to a database of over 400,000 present-day individuals from the UK. The analysis showed that the MS-associated gene variations persisted primarily in the north, the direction of the Yamnaya migration, rather than in southern Europe.

In Denmark, the Yamnaya significantly replaced ancient farmers, making them the direct ancestors of modern Danes. Notably, Scandinavian countries display higher MS rates, suggesting a strong correlation between the Yamnaya ancestry and the disease.

Although the mechanism by which these gene variants influence MS susceptibility remains unclear, one possibility is the differing exposure to animal-based infections among modern humans. It is speculated that such exposures may disturb the balance of the immune system, potentially contributing to the development of MS.

While the study provides a compelling explanation for the north-south MS divide in Europe, further research is needed to validate these findings and gain a more comprehensive understanding of the underlying mechanisms. Genetic expert Dr. Samira Asgari of Mount Sinai School of Medicine emphasizes the need for continued investigation in an accompanying commentary.

The study's groundbreaking use of ancient DNA highlights the power of genetic research in unraveling the mysteries of human history and disease susceptibility. With these insights, scientists can continue to explore new avenues for understanding and potentially treating diseases like MS.