In a stunning revelation, ancient DNA has shed light on why northern Europeans have a higher risk of multiple sclerosis (MS) compared to other ancestries. According to researchers, this heightened risk can be traced back to a genetic legacy from Bronze Age horse-riding cattle herders who migrated to the region about 5,000 years ago.
This groundbreaking finding is a result of a monumental project that involved comparing modern DNA with that extracted from the teeth and bones of ancient humans. By analyzing both prehistoric migration patterns and disease-linked genes, scientists gained a valuable insight into the origins of MS and its prevalence in certain populations.
The study unveiled that when the Yamnaya, a Bronze Age people from the steppes of Ukraine and Russia, arrived in northwestern Europe, they carried certain gene variants associated with an increased risk of MS in present-day populations. Surprisingly, these genetic variants not only aided the Yamnaya in flourishing but also provided protection against infections transmitted by their cattle and sheep.
William Barrie, a genetics researcher at the University of Cambridge and co-author of the study, expressed his astonishment at the findings. 'What we found surprised everyone. These variants were giving these people an advantage of some kind,' he emphasized.
This extraordinary research project, led by Eske Willerslev from Cambridge and the University of Copenhagen, marks the first gene bank of its kind. It boasts thousands of samples gathered from early humans in Europe and western Asia, expanding our knowledge of ancient DNA and its implications.
Given the prevalence of MS among white individuals with northern European ancestry, exploring the disease through this gene bank seemed like a logical first step. Although MS can affect any population, it is most commonly observed in individuals of northern European descent—a phenomenon that has puzzled scientists until now.
Multiple sclerosis is a debilitating disease where the immune system mistakenly attacks the protective coating on nerve fibers, causing gradual erosion. Symptoms vary from person to person and can include numbness, tingling, impaired walking, and vision loss. While the exact cause of MS remains elusive, one prevailing theory suggests that certain infections can trigger the disease in genetically susceptible individuals. Over 230 genetic variants have been identified to increase the risk of MS.
The research team began by examining the DNA of approximately 1,600 ancient Eurasians, thus uncovering significant population shifts in northern Europe throughout history. First, farmers from the Middle East displaced hunter-gatherers, and then, 5,000 years ago, the Yamnaya made their way into the region, accompanied by horses and wagons, as they herded cattle and sheep.
To determine whether MS-linked genetic variations persisted in the north, the team compared the ancient DNA to the genetic data of around 400,000 present-day individuals stored in a UK gene bank. The results showed that these genetic variants were more prevalent in northern Europe, where the Yamnaya had settled, as opposed to southern Europe.
The researchers also noted that in what is now Denmark, the Yamnaya quickly replaced the ancient farmers, making them the closest ancestors of modern-day Danes. Importantly, Scandinavian countries have some of the highest rates of MS in the world.
But how could gene variants that were once advantageous for ancient immunity end up playing a role in an autoimmune disease like MS? Dr. Astrid Iversen from Oxford University, a co-author of the study, suggests that differences in how modern humans are exposed to animal germs may disrupt the balance of the immune system.
While these findings offer a plausible explanation for the north-south divide in MS prevalence across Europe, Samira Asgari, a genetic expert from New York's Mount Sinai School of Medicine, reminds us that further research is needed to confirm the link.
The discovery of this genetic legacy sheds new light on the complex interplay between past migrations, ancient DNA, and the prevalence of diseases in specific populations. With continued advances in genetic research, we inch closer to unraveling the mysteries that have plagued our understanding of diseases like MS for decades.
