DNA from ancient humans is providing some vital clues about the emergence of multiple sclerosis and other devastating neurodegenerative conditions. In a series of new research papers out this week, scientists detail evidence that many genetic variants linked to MS first began to spread globally about 5,000 years ago, from populations living in Eastern Europe and Central Asia. These variations likely protected people at the time from infectious diseases but now might explain why those native to Northwestern Europe have higher rates of MS to this day.
The research is part of an extensive collaboration between scientists from around the world, including the UK, U.S., and Denmark. For the past five years, the team has been collecting and analyzing the DNA remnants of nearly 5,000 ancient humans who lived throughout Europe and Asia, in an effort that they’ve billed as the largest ancient human gene bank ever assembled. These DNA samples, collected from teeth and bones, stretch from the Mesolithic era (the Middle Stone Age) through the Middle Ages, with the oldest dated 34,000 years ago. The team’s first batch of peer-reviewed research from this project—four papers in total—was published Wednesday in Nature.
One of the major findings from this research concerns multiple sclerosis, an autoimmune condition that saps away a person’s myelin sheath, the protective layer that covers our nerves. People with MS experience many neurological symptoms, including numbness, muscle weakness, pain, and difficulty walking. Often these symptoms will come and go at first, but many patients eventually experience progressively worse illness and declining quality of life.
In recent years, it’s become clear that the Epstein-Barr virus is likely a leading cause of MS. But while nearly everyone in the world is exposed to the virus at some point in their lives, only a small percentage ever develop MS. So it’s obvious that there are other factors that can make someone more vulnerable to it, including our genetics. By comparing ancient DNA to the genes of people living today, the scientists behind this new research say they’ve figured out how some of these MS-linked genes emerged and later spread globally.
The team found that these variants first showed up among people living in the Pontic Steppe, which covers parts of modern-day Romania, Ukraine, and Russia. Some 5,000 years ago, these genes began to spread into Northwestern Europe through the migration of the Yamnaya people. The Yamnaya people were predominantly livestock herders, and the researchers believe that these variants probably provided some protection against germs caught from their animals—a benefit that outweighed the risk of MS, which tends to show up between the ages of 20 and 40.
“It must have been a distinct advantage for the Yamnaya people to carry the MS risk genes, even after arriving in Europe, despite the fact that these genes undeniably increased their risk of developing MS,” said study author Eske Willerslev, a professor at the Universities of Cambridge and Copenhagen and project director, in a statement. “These results change our view of the causes of multiple sclerosis and have implications for the way it is treated.”
The genetic legacy of the Yamnaya people continues to this day, the study authors note. Many people in Northwestern Europe can trace their lineage back to the Yamnaya, for instance, and the area is known for its relatively higher prevalence of MS. It’s not just MS that has its roots in the DNA of our ancestors; the team also published a study this week finding that some genes tied to a higher risk of Alzheimer’s and type 2 diabetes originated in hunter gatherers.
The team will continue investigating how these and other diseases might have been shaped by our ancestors. They also eventually plan to make their ancient gene bank open access, so that other researchers can easily examine the samples as well.
“These results astounded us all. They provide a huge leap forward in our understanding of the evolution of MS and other autoimmune diseases. Showing how the lifestyles of our ancestors impacted modern disease risk just highlights how much we are the recipients of ancient immune systems in a modern world,” said co-author William Barrie, a postdoc in the University of Cambridge’s Department of Zoology, in a statement.