Multiple sclerosis is more common among white Europeans. Researchers studying ancient DNA may have figured out why.

• Researchers compared DNA from hundreds of ancient teeth and bones to DNA from modern humans.
• They wanted to find out how genes linked to diseases like multiple sclerosis originated and spread.
• They found genetic susceptibility for MS may be linked to a population of ancient herders.

Genes that may have once helped ancient herders fight infectious parasites could contribute to autoimmune diseases today, like multiple sclerosis.