Ancient genetic material sheds light on the reason why individuals of northern European descent are more susceptible to multiple sclerosis compared to other ethnicities. This can be attributed to the genetic inheritance from horse-riding cattle herders who migrated into the area approximately 5,000 years ago.

The results are from a large study that compared current DNA with DNA extracted from the teeth and bones of ancient humans. This allowed researchers to track prehistoric migration patterns and identify disease-related genes that were present.

On Wednesday, researchers stated that when the Yamnaya, a group of people from the Bronze Age, migrated from the steppes in present-day Ukraine and Russia to northwestern Europe, they brought with them gene variants that have been linked to a higher risk of multiple sclerosis in modern times.

However, the Yamnaya thrived and spread these genetic variations. The study published in Nature suggests that these genes may have also provided immunity to diseases carried by their livestock.

“The results of our research were unexpected,” stated William Barrie, a genetics expert from the University of Cambridge. “These genetic variations were providing these individuals with some type of benefit.”

This discovery is a result of a unique genetic database containing numerous samples from ancient humans in Europe and western Asia. The project was led by Eske Willerslev, a pioneer in the field of studying ancient DNA, from Cambridge and the University of Copenhagen. Previous studies have also identified prehistoric human relatives, including Neanderthals.

The initial step of utilizing the latest gene database to investigate MS was a rational decision. This is due to the fact that although MS can affect any demographic, it is particularly prevalent among individuals of white European descent, and researchers have yet to determine the cause.

The potentially disabling disease occurs when immune system cells mistakenly attack the protective coating on nerve fibers, gradually eroding them. It causes varying symptoms — numbness and tingling in one person, impaired walking and vision loss in another — that often wax and wane.

The exact cause of MS is still unknown, but one prominent theory suggests that certain infections may activate it in individuals with a genetic predisposition. Over 230 genetic variations have been identified that could raise the likelihood of developing MS.

The initial focus of the study was analyzing the genetic material of approximately 1,600 ancient individuals from Eurasia. This revealed significant changes in the population of northern Europe. Initially, farmer populations from the Middle East began to replace hunter-gatherers. Later, around 5,000 years ago, the Yamnaya people migrated into the region with their horses and wagons, as they were primarily nomadic herders of cattle and sheep.

The scientists analyzed the ancient DNA and compared it to a database of 400,000 individuals currently living in the UK. They were specifically looking for genetic variations linked to MS and discovered that these variations were more prevalent in the north, where the Yamnaya people migrated, rather than in southern Europe.

According to Willerslev, the Yamnaya people quickly replaced the indigenous farmers in present-day Denmark, making them the most closely related ancestors of present-day Danes. Scandinavian countries have particularly high rates of multiple sclerosis.

How could genetic variations that were thought to have enhanced immunity in the past contribute to the development of an autoimmune disorder? According to Dr. Astrid Iversen from Oxford University, this could be attributed to differences in modern humans’ exposure to animal-borne pathogens, which may disrupt the balance of the immune system.

The results provide a possible reason for the discrepancy in rates of multiple sclerosis between northern and southern Europe. However, genetic specialist Samira Asgari from Mount Sinai School of Medicine in New York, who was not involved in the study, cautioned that further research is necessary to validate this connection. She shared her thoughts in a commentary accompanying the findings.

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