A flight of studies one genetic researcher called a “tour de force” has indicated the surprising genesis of multiple sclerosis in Europe.
Four related papers, published in Nature, sourced over 1,600 ancient genomes to trace the origins of various genetic traits in modern Europeans. They found certain characteristics, including a higher risk for multiple sclerosis (MS) and the persistent ability to digest milk, arrived in Europe via three distinct migration waves starting 45,000 years ago.
This migration pattern and the mechanisms that drove it are already familiar to scientists. What we didn’t know is that population mixing played less of a role in genetic development than previously thought — and that traits like MS may once have provided evolutionary advantages.
That’s a bombshell, because MS is a notoriously persistent auto-immune disorder that attacks the protective coatings of nerve cells in the brain. How could such an insidious disease help its host?
How multiple sclerosis works. Photo: Wiki Commons
Three major migrations
The research contends that the three major migrations influenced current European genetics. Hunter-gatherers first reached Europe from Asia around 45,000 years ago. Farmers then came from the Middle East 11,000 years ago. Finally, animal herders came from western Asia and eastern Europe 5,000 years ago.
The team sampled DNA from 317 skeletons in Europe that dated from the last two migrations, 3,000 to 11,000 years ago. They then included information on file from over 1,300 other ancient Eurasians.
Finally, they compared these ancient genomes with UK Biobank DNA of over 410,000 modern individuals. That enabled them to identify direct links between certain traits and specific migrations.
Lactase, for instance, is the chemical the body needs for processing milk. Humans developed better lactase persistence over time. The study suggested mutations near the lactase gene could have helped our European ancestors survive famines before the mass arrival of animal herders 5,000 years ago.
MS traveled to Europe at roughly the same time, the researchers found. After the west Asian herders’ arrival, it started to spread throughout northern Europe during subsequent millennia. A strong evolutionary advantage helped it along; but why?
A hyperactive immune system has its uses
Because MS stems from immune overactivity, the researchers speculated that the trait could have helped ancient populations survive plagues and common pathogens.
After all, when you’re encountering a brand new world, it’s common to find all kinds of diseases and bugs your immune system doesn’t have an answer for. Adaptation is inevitable — but one other survival strategy in these conditions is simply to scorch the earth.
That’s exactly what some populations did, according to the study. Contrary to expectations, some immigrating populations entirely replaced existing ones. Newcomers in Denmark, for example, eradicated locals rather than coexisting with or displacing them.
