Ancient DNA reveals origins of Multiple Sclerosis in Europe

News Excerpt:

As per the results published in the journal “Nature”, this particular team of scientists has taken a “clever” approach to understanding ancient humans by looking at how ancestry affects modern traits, rather than trying to figure out the traits by looking only at ancient DNA samples. 

About the news:

Key highlights:

  • The findings provide evidence that differences in migrants’ dispersal patterns caused some of the regional variation in certain traits. 
    • That contradicts the idea that genetic differences arose mainly as people adapted to conditions in specific European locations.
  • More than 1,600 ancient genomes have helped to trace the roots of a host of genetic traits found in modern Europeans. 
    • The genomes suggest that many characteristics — including a heightened risk for multiple sclerosis — were carried to Europe by people who migrated to the continent in three distinct waves starting around 45,000 years ago.

New arrivals

  • Europe was settled by anatomically modern humans in three main waves: 
    •  Hunter-gatherers reached Europe from Asia around 45,000 years ago.
    •  Farmers arrived from the Middle East 11,000 years ago.
    •  Pastoralists — animal herders — came from the steppes of western Asia and eastern Europe 5,000 years ago. 
  • Archaeologists and historians had assumed that these groups mixed with one another throughout the continent and that populations in particular places evolved distinct traits in response to their local environments. But, this is not the whole story, it is expected that some of these migrants completely replaced the existing populations.

Genes and geography

  • The dispersal patterns mean that many modern Europeans carry some genetic ancestry from all three population waves, but the relative amount of each varies depending on the location.
  • Next, the researchers compared the ancient genomes with those of 410,000 modern individuals whose genetic profiles are stored in the UK Biobank, a massive database of genetic and physical information. 
    • The data provided clear evidence that many traits trace back directly to one of the three migration waves.

Evolutionary mysteries

  • One of the traits that seems to have had a strong evolutionary advantage is one associated with a predisposition to multiple sclerosis. 
  • This trait arrived in Europe with the west-Asian pastoralists and became even more common in northern Europe over the subsequent millennia.
  • Today, multiple sclerosis is a devastating disease but that superpowered immune system, or genetic variants associated with it, could have helped ancient people to survive plagues and common pathogens.
  • This research provides unprecedented detail on how ancient ancestry can influence disease risk to this day.

About Multiple Sclerosis(MS):

  • It is a long-lasting chronic disease of the central nervous system
  • It is an immune-mediated disease. This means that an abnormal response of the body’s immune system causes the disease. In this case, the immune system attacks the central nervous system (CNS) by mistake. The CNS is made up of the brain, spinal cord, and optic nerves.
  • It is an unpredictable disease that affects people differently. Some people with MS may have only mild symptoms. Others may lose their ability to see, write, speak, or walk when communication between the brain and other parts of the body becomes disrupted.
  • Myelin is the fatty tissue that surrounds and protects nerve fibers. In MS, the myelin is destroyed in many areas. This loss of myelin forms scar tissue called sclerosis. These areas are also called plaques or lesions. When the nerves are damaged in this way, they can’t conduct electrical impulses to and from the brain.

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