Genetic researchers at the University of Cambridge in Britain say ancient DNA shows why northern Europeans have a higher risk of getting a nerve disease than other Europeans.
The disease is called multiple sclerosis or MS. The researchers said the risk lies in genes from horse-riding cattle herders who entered northern Europe about 5,000 years ago.
The findings come from a huge project to compare modern DNA with ancient genetic material taken from human remains including teeth and bones.
A study released last year said it identified the earliest evidence of horse riding in people called the Yamnaya. The scientists say they lived 4,500 to 5,000 years ago during the Bronze Age period of human history.
The Yamnaya moved from the grasslands of what is now Ukraine and Russia into northwestern Europe. However, the researchers say those people carried gene versions that today are known to increase a person’s risk of multiple sclerosis.
The researchers added that they believe the same genes protected those herders from infections from their cattle and sheep.
The research was published in Nature, a scientific publication.
William Barrie is a genetic researcher at Cambridge. He helped write the study. He said everyone involved was surprised. “These variants were giving these people an advantage of some kind,” he said.
The finding was made possible by a gene bank with thousands of examples of early humans in Europe and western Asia. That project is led by Eske Willerslev of Cambridge and the University of Copenhagen in Denmark.
While MS can strike any population it is most common among white descendants of northern Europeans. Scientists have been unable to explain why.
The cause of the disease is not known. However, one theory is that infections could cause it in people who have certain genetic qualities. Scientists say they have found 230 genetic variants that might increase the risk of MS.
The researchers studied DNA from about 1,600 ancient Eurasians. They used the information to develop of map of population movements in northern Europe. They said farmers from the Middle East began pushing out hunter-gatherers about 5,000 years ago. Then the Yamnaya moved in. They traveled with horses and wagons and herded cattle and sheep.
The research team compared the ancient DNA to the genetic information of 400,000 modern-day people stored in UK Biobank in Britain. They wanted to see if MS-linked genetic variations persisted in the north. That is the part of Europe where the Yamnaya moved, rather than southern Europe.
In what is now Denmark, the Yamnaya replaced ancient farmers, making them the closest ancestors of modern Danes, Willerslev said.
Rates of MS are especially high in the northern part of Europe known as Scandinavia.
The findings raise additional questions and suggest a need for more research. One of the writers of the study, Astrid Iverson of Oxford University, questioned why a gene variant that seems to have strengthened immunity later plays a part in causing what is believed to be an autoimmune disease. Differences in how modern humans are exposed to animal germs might push the immune system out of balance, she said.
I’m Mario Ritter, Jr.
Lauran Neergaard reported this story for the Associated Press. Mario Ritter, Jr. adapted it for VOA Learning English.
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Words in This Story
herder –n. a person who keeps and cares for animals that live in large groups like cattle and sheep
variant –n. a version of something that has a small difference
advantage –n. something that makes success more likely
immunity –n. the ability to resist disease
autoimmune disease –n. a condition in which the body’s own defenses against infection attack substances that the body itself creates