How Snails Point to the Trails of Ancient Seafarers in Ireland

Laura Holden

Cepaea nemoralis, a common land snail, may have been brought over to Ireland when European travelers came over to settle there.

When a group of French or Spanish travelers sailed the Atlantic to Ireland about 8,000 years ago, they carried along a species of snails that today bear genetic witness to their passage. The snails might have been stowaways — or maybe they were just snacks.

Irish land snails today possess certain genetic markers that are shared solely with snails living in the northern Spain and southern France. A single delivery by humans — whether as cargo or escargot — is the best explanation for the genetic relationship between the two geographically distant species, researchers at the University of Nottingham suggest.

"It's a packed lunch that they would have carried around with them," Angus Davison, an evolutionary biologist at the University of Nottingham. 

... "This work suggests quite strongly that they were taken to Ireland by Spanish people, which is still a bit weird, because why would they do it?" Jones said, "[If this was] anywhere else you'd think they were mad," but in parts of France and Spain, where cave dwellings with millions of snail shells have been discovered, there's strong evidence that snails were a dietary staple. As Jones explained: "What's easier, to chase down a woolly mammoth and eat it, or pick up a lot of snails?"

When those cave dwellers moved, they may have taken snails along. "While they weren't the first humans, this lot came from France ... without stopping along the way," Davison explained. If they stopped en route to go ashore for long, the snails would have died, or been found in other parts of Europe, too. "It tells you about a single event," he said.

Davison and Adele Grindon (then a graduate student at the University of Nottingham) spent two years collecting samples of the snail species Cepaea nemoralis from Ireland, Britain, Northern Spain and Southern France. Then they analyzed the mitochondrial DNA of the specimens — an easy section to sequence, Davison explained. They found seven snail lineages around Europe, one of which was unique to only two places: Ireland and the slopes of the Pyrenees.  

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