Ancient genes predisposing people to multiple sclerosis (MS) may have spread due to the protection they afforded against infectious diseases thousands of years ago.
A major migration of sheep and cattle herders 5000 years ago appears to have introduced genes that increased the risk of MS into northern Europe, where it is around twice as common as in the south.
While these genes conferred protection against diseases carried by the livestock they were also linked with MS, an autoimmune disease affecting nerves in the brain and spinal cord.
The findings published in Nature, which are included as part of four research papers with overlapping authors, also revealed genes increasing the risk of Alzheimer’s disease and Type 2 diabetes in hunter gatherers.
Collectively, they show how prehistoric genomes have shaped modern populations.
Study co-author William Barrie, PhD, a postdoc in the University of Cambridge’s zoological department, said the researchers were “astounded” by the results.
“They provide a huge leap forward in our understanding of the evolution of MS and other autoimmune diseases,” he explained.
“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.”
The findings come from the world’s largest ancient human gene bank, amassed from bones and teeth from humans in multiple museum collections, the oldest of which lived around 34,000 years ago.
The database encompasses the Mesolithic and Neolithic areas, Bronze and Iron Ages, the Viking period and into the Middle Ages.
Barrie and colleagues compared this ancient DNA with that of around 410,000 people living in modern Britain, which is held in the UK Biobank.
The results showed that genes associated with MS were introduced into north-western Europe by the Yamnaya people, who herded livestock and migrated east from the Pontic Steppe region, which includes parts of Ukraine, south-west Russia and western Kazakhstan.
While the genes protected these people from animal-borne infectious diseases, they also conferred an increased risk of MS—a disease that has been previously linked with almost 230 genes that increase its risk by almost a third.
Other research in Nature adds evidence to the way in which genetic selection and migration in ancient humans impacted on modern European populations.
One study using genomic data sequenced from ancient humans showed a distinct genetic impact from transitioning from hunter gatherers to farmers.
Other research linked diabetes and Alzheimer’s genes to Western hunter-gatherer populations, whereas the increased average height of northern versus southern Europeans came from other, Steppe-related ancestry.
A final investigation examining a hundred ancient Danish skeletons showed genetic patterns in changing land use, diet, culture, and population demographics.
Researcher Astrid Iversen, PhD, from the University of Oxford, said: “We now lead very different lives to those of our ancestors in terms of hygiene, diet, and medical treatment options and this combined with our evolutionary history means we may be more susceptible to certain diseases than our ancestors were, including autoimmune diseases such as MS.”
Lars Fugger, PhD, a professor at the University of Oxford, added: “This means we can now understand and seek to treat MS for what it actually is: the result of a genetic adaptation to certain environmental conditions that occurred back in our prehistory.”
The studies may help explain the origin of other neurodegenerative diseases and could also shed light on genetic markers for autism, ADHD, schizophrenia, bipolar disorder, and depression.