Scientists believe a genetic similarity between snail fossils found in Ireland and the eastern Pyrenees suggests humans migrated from southern Europe to Ireland 8,000 years ago.
The origins of flora and fauna that are only found in Ireland and Iberia, but which are absent from intervening countries, is one of the enduring questions of biogeography.
Snails in Ireland today are almost identical to snails in southern France and northern Spain.
But they are genetically distinct from those found in Britain.
In a study published in PLOS One, researchers argue that "the most likely justification for the specific connection between Irish and Pyrenean Cepaea nemoralis is human-assisted movement of snails".
"There are records of Mesolithic or Stone Age humans eating snails in the Pyrenees, and perhaps even farming them," co-author of the study Angus Davison from the University of Nottingham told BBC News.
"If the snails naturally colonised Ireland, you would expect to find some of the same genetic type in other areas of Europe, especially Britain. We just don't find them.
"The highways of the past were rivers and the ocean, as the river that flanks the Pyrenees was an ancient trade route to the Atlantic.
"What we're actually seeing might be the long lasting legacy of snails that hitched a ride as humans travelled from the south of France to Ireland 8,000 years ago.
"The intriguing implication is that the genetics of snails might shed light on a very old human migration event."