Teams from the Universities of Cambridge and Copenhagen have published new research this week linking the origins of MS to prehistoric migration.
Herding peoples spread out from the steppes of Western Asia over 5000 years ago. They brought with them genes that increase the risk of getting MS. People from north-western Europe and Scandinavia are more likely to carry these genes than other Europeans. This may explain why MS is more common in countries like the UK, Ireland, Sweden and Iceland.
Researchers from Cambridge and Copenhagen compared modern genetic variation with a database of ancient DNA samples. They were able to link the genes known to increase MS risk to the ancient herding peoples that colonised Europe from the steppe region around modern Ukraine and southern Russia.
You can read media reports on this research here.
How did this happen?
As generations of people live, reproduce and die, genes that give protection from the dangers of that time will become more common. However, these genes may come with unwanted side effects. A gene that protects you from a deadly parasite or fatal disease may make you more susceptible to another illness like cancer or MS. But if the infectious disease is very dangerous, it could be worth the trade-off.
Animal diseases first became a significant risk for humans when they developed lifestyles based around cattle, sheep and other herd animals. Living with their herds, the herding peoples of the steppe were exposed to new diseases. They developed genetic protection against them over 5000 years ago, and these are the same genes that are linked to MS risk. The herding lifestyle was successful and the herders spread out into new territories across Scandinavia and Northern Europe, and mixed with the hunter-gather and farming peoples already there.
For hunter-gathering people, getting a reliable supply of food could have been difficult, so they developed genetic protection against famine. In modern times, those genes are linked to diabetes risk. Early farmers lived in towns and cities, so infectious diseases were a danger for them. The researchers found that steppe herder genes may also contribute to north-western Europeans being taller than southern Europeans, having a lower risk of getting Alzheimer's disease and the ability to digest milk products as adults.
Fast forward to modern times, where famine and infectious diseases are no longer a significant cause of death and disease in Europe. We still have the prehistoric genes that protected our ancestors, but now it's the trade-offs that came with them that affect our health.
