Ancient DNA helps trace the origins of multiple sclerosis in European descendants

5,000 years ago, sheep and cattle herders migrated from Asia to Europe, bringing with them their pastoralist lifestyle and an increased risk of multiple sclerosis, according to a new Harvard University study. DNA For thousands of people past and present.

This discovery answers a long-standing mystery in medical science: Why is this debilitating autoimmune disease more common in people from northern Europe? The research also reframes the modern disease, suggesting that its origins go back to an evolutionary compromise.

the Multiple sclerosis It is a neurological disease in which a person's natural immune system turns against his or her nervous system. Thousands of years ago, as people began living around livestock and their germs, immune-related gene variants began to give humans an evolutionary advantage, perhaps because they helped strengthen defenses against attack by microorganisms. Infections And Parasites They carried their animals.

But genes don't do just one thing. In a prehistoric world rife with infectious dangers, a strong immune response could mean the difference between life and death. Thousands of years later, these same genetic variants also increase the risk that their descendants will suffer from an uncontrolled immune response to MS.

For many years, researchers have debated the “hygiene hypothesis,” which is the idea that… asthma waves Allergies It may be the result of modern life that is too clean to allow the immune system to develop. The new paper details how variants of certain genes linked to the immune system became more common because they gave people an evolutionary advantage thousands of years ago.

“What was perfected over 5,000 years and improved in our evolution is essentially what we are trying to combat today,” said Lars Fugger, a professor of neuroimmunology at UCLA. Oxford university Who cares for patients with multiple sclerosis and is one of the authors of the article. “So there's no puzzle that's too difficult to deal with.”

The study, one of four published Wednesday in the journal natureis part of a larger effort to analyze DNA They have been recovered from ancient human remains and reveal the origin and evolution of various traits and disease risks. Researchers also discovered, for example, that a version of a gene called APOE4 Which increases the risk of suffering Alzheimer's disease It was probably introduced to European populations by hunter-gatherers.

“Processes that occurred thousands of years ago have clear and profound impacts on the health and longevity of people today,” said Ivan Irving Pease, study author and assistant professor of population genetics at the University of Copenhagen.

analysis DNA Ancient traces extracted from bones or teeth have rewritten our understanding of human prehistory, providing new data on the waves of migration that gave rise to modern populations.

Researchers already know, for example, that the population of Europe today is made up of three main waves of migration: hunter-gatherers who arrived in the region 45,000 years ago, farmers who arrived from the Middle East about 11,000 years ago, and pastoralists who migrated from the Middle East. Pontic steppe, a grassland extending from Central Europe to Central Asia, about 5,000 years ago.

But potential DNA Changing our understanding of human biology has so far been limited by a lack of DNA in sufficient samples, he said. David Reicha geneticist who studies DNA old in Harvard university And those who did not participate in the new studies.

In their latest work, the scientists analyzed… DNA It includes more than 300 individuals, a third of them from Denmark, who lived between 25,700 and 1,200 years ago. They included a father buried alongside his young son, a hunter-gatherer called Dragsholm Man, who adopted the diet of migrant farmers, and Bursmus Man, who was discovered in a swamp with an arrow through his nose and sternum.

By combining this data with previously sequenced ancient samples, they created a database of 1,600 ancient genomes from across Eurasia.

He explained that the goal is to create a database containing 5,000 ancient genomes that will help scientists search for the roots of disease risks and their spread. Eski WillerslevAn evolutionary geneticist at the University of Cambridge and leader of the project.

So far, ancient DNA reveals that basic traits, such as height and disease risk, first evolved outside Europe and were imported into the population through multiple waves of migration.

“In terms of our susceptibility to disease and our appearance, it was largely created by these migration events,” says Willerslev.

the Multiple sclerosis It is a complex disease, caused by a combination of environmental and genetic factors that are only partially known. but, Lawrence Steinmanneurologist stanford medicine He, who was not involved in the research, said the new work provides a fascinating and provocative line of evidence that traces genetic risk back to ancient populations.

“MS usually doesn't affect you until you're a young adult, so you could have spread and increased the population and had offspring before the manifestations of MS develop — and these genes can give you an advantage against some types of infections.” Steinman said.

The idea that infectious diseases helped shape human evolution is not new, but the researchers said they were still surprised to see such a clear signal that MS risk genes had been “positively selected,” meaning they increased in frequency because they provided Evolutionary advantage. .

but, Samira Asgharicomputational biologist in Icahn School of Medicine at Mount Sinai He, who has dedicated himself to understanding the human genetics of infection and immunity, said the specific advantage suggested by the articles — greater protection against infection — is a plausible explanation, but remains a hypothesis.

“This is the part that needs more research to prove,” Asghari said.

The researchers have other work, not yet peer-reviewed, that shows an explosion in pathogens jumping from animals to humans about 5,000 years ago, which they say could bolster the argument that pathogens surrounding early Europeans shaped their genes.

“What we see consistently in the immune system is that genes are selected based on which pathogens the population encounters over time,” says Astrid Iversen, professor of virology and immunology at the University of Oxford.

Many experts cautioned that delving into the genetic roots of human diseases will not directly lead to new treatments, but they can't rule that out either. “Understanding biology from different angles can accelerate progress toward better medicines,” Asghari said.

Washington Post