Savagnin blanc — not to be confused with the sauvignon blanc the sommelier recommended with your cheese course — is a fruity, acidic grape from the vine-encrusted hills of Jura, near France’s border with Switzerland. And if you visit and sip the region’s white wines today, you’ll be tasting the exact same grape, down to the genetic level, that has gone into its wines for at least 900 years.

“It’s kind of frozen in time,” said Nathan Wales, an archaeologist at the University of York in the UK and the lead author of the paper, published Monday in the journal Nature Plants. “I had assumed that they were just recycling the names, and lineages would come and go, but we can see that’s not the case.”

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The study followed an analysis of the DNA of 28 grape seeds found in wells and latrines at various archaeological sites in France, where crushed wine grapes were dumped, or simply excreted by animals or people who ate them. Dr. Wales’s team then compared those sequences to GrapeReSeq, a genetic bank for contemporary wine grapes.