Insights from ancient human DNA provide clues to the high prevalence of multiple sclerosis in present-day northern Europeans.
The prevalence of multiple sclerosis in northern Europeans can be attributed to a genetic inheritance from horseback-riding cattle herders who migrated into the region around 5,000 years ago. This conclusion is based on the analysis of ancient DNA alongside modern genetic data, shedding light on both historical population movements and the introduction of disease-related genes. As the Yamnaya people from the Bronze Age journeyed from the Ukraine and Russia steppes into northwestern Europe, they brought along gene variants associated with an elevated risk of multiple sclerosis, according to researchers. (source)
The Yamnaya people thrived and spread these genetic variations, which likely provided protection against infections from their livestock, as concluded in a study published in the journal Nature.
“This discovery was quite surprising to everyone,” stated William Barrie, a genetics researcher at the University of Cambridge and co-author of the study. “These genetic variations appear to have given these individuals some form of advantage.”
This is one of several findings stemming from a groundbreaking genetic database containing thousands of samples from early human populations in Europe and western Asia. The project is led by Eske Willerslev of the University of Cambridge and the University of Copenhagen, a pioneer in the study of ancient DNA. Similar research has also identified even earlier human relatives, such as Neanderthals.
The logical first step in exploring MS was to utilize the new gene bank. This is because while MS can affect any population, it is most prevalent among individuals of white Northern European descent, and scientists have yet to ascertain the reason for this disparity.
This potentially debilitating disease arises when immune system cells erroneously attack the protective coating on nerve fibers, gradually causing their deterioration. It leads to diverse symptoms – such as numbness and tingling in one individual, impaired walking and vision loss in another – which often fluctuate over time.
The cause of MS remains unclear, although a leading theory suggests that certain infections could trigger it in genetically susceptible individuals. Over 230 genetic variants have been identified that may heighten the risk for this condition.
The initial analysis involved studying DNA from approximately 1,600 ancient Eurasians and identifying significant population changes in northern Europe. Initially, farmers from the Middle East started overtaking hunter-gatherers, and around 5,000 years ago, the Yamnaya people began migrating with horses and wagons, herding cattle and sheep.
The research team compared the ancient DNA with data from around 400,000 present-day individuals stored in a UK gene bank to observe the persistence of MS-linked genetic variations in the north, where the Yamnaya migrated, rather than in southern Europe.
In what is now Denmark, the Yamnaya swiftly replaced ancient farmers, establishing themselves as the closest ancestors of modern Danes, according to Willerslev. The prevalence of MS is notably high in Scandinavian countries.
Dr. Astrid Iversen from Oxford University suggested that gene variants which were once thought to enhance ancient immunity may now be contributing to autoimmune diseases due to differences in modern humans’ exposure to animal germs, potentially disrupting the balance of the immune system. This may explain the geographical divide in multiple sclerosis (MS) prevalence between northern and southern Europe. However, genetic expert Samira Asgari from New York’s Mount Sinai School of Medicine cautioned that further research is necessary to confirm this link, as stated in an accompanying commentary.
