Ancient DNA provides new insights – “The immune system lost its job”

Ancient bone remains from our ancestors have provided new insights into the prevalence of multiple sclerosis. By looking back in time, researchers can provide a possible explanation for why the disease is more prevalent in northern Europe.

At the beginning of the Bronze Age, significant demographic changes took place in Europe, which is still reflected in our DNA today. The so-called Yamnaya people moved from the Pontic-Caspian steppe, today’s Ukraine, to Neolithic Europe. And in Northern Europe, we presently have the highest frequency of steppe genes.

A research project led by researchers at the University of Copenhagen has examined genetic traces and geographical migration using a biobank of 5,000 prehistoric human genomes. The researchers now believe they may have found an explanation as to why multiple sclerosis (MS) is particularly prevalent in northern Europeans.

Previous research has shown that genes linked to the immune system can influence the risk of developing MS, but the origin of these genes has not been explained – until now.

The Yamnaya people lived as nomads, herding sheep and cows. Their migration to Europe is believed to have included genes for lactotolerance, which means that today most Europeans can tolerate milk. However, some of the inherited genes are now having a negative effect.

“In past times, when humans lived in close proximity to animals, they were exposed to various bacteria and viruses against which the immune system developed a defence. Up until recently, these genes were very useful. We have been able to prove that the recent rapid increase in the occurrence of multiple sclerosis can be linked to increased hygiene,” says Kristian Kristiansen, Professor of Archaeology at the University of Gothenburg and one of the researchers behind the study.

The extent to which people have contact with animals and their bacteria seems to make a difference because now it appears that the genes and the immune system, which were once meant to protect us from infections, are running amok in some cases. Kristian Kristansen, who grew up on a farm, suggests that a little bit of “animals and dirt” can benefit young children, which we are not exposed to in the same way as our ancestors.

“The immune system lost its job and has now started attacking its own body instead.”

MS is a chronic inflammatory disease in which the white blood cells of the immune system enter the central nervous system and attack the so-called myelin, the insulation of the nerve fibres needed for nerve impulses to be transmitted. MS causes inflammation that can damage the nerve fibres, which in turn can cause nerve impulses to be misdirected. Common symptoms of the disease include balance problems, tremors and sensory disturbances.

The MS study is part of a larger research project in which researchers have been trying to gain a better understanding of brain diseases such as MS, Alzheimer’s and Parkinson’s, using disciplines ranging from archaeology to medicine. The research findings were recently published in Nature.

“I hope that this knowledge can be used productively and positively to understand better the underlying cause and ways to treat it,” Kristansen says.

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