A study has found that 2 separate groups of snails, one in Ireland and one in the Pyrenees, share DNA markers not found elsewhere in Europe. The snail trail leads to an ancient sea journey 8,000 years ago, when humans brought them along as fast food.
A team led by Angus Davison, an evolutionary geneticist at the University of Nottingham, studied the mitochondrial DNA of nearly 900 Cepaea nemoralis snails across their European range. They found a rare shared lineage between samples from Ireland and the Eastern Pyrenees, along the Spanish-French border, but nowhere in between – except for isolated examples in Toulouse, the Isle of Man, and a single specimen from Wales.
The distinctive-looking snails have one-inch long, white-lipped shells and, according to fossil evidence, first appeared in Ireland about 8,000 years ago. They had lived in southern Europe for tens of thousands of years before that. The Pyrenean haplotypes dominate most Cepaea nemoralis populations across Ireland today, probably because they arrived there first.
The findings suggest that the snails were intentionally brought from Iberia to Ireland by Mesolithic coast-hugging sea travellers as a source of food. Archaeologists have previously discovered deep middens of burnt Cepaea nemoralis shells in Pyrenean caves dating back 11,000 years, and they are commonly found in other Mediterranean archaeological sites prior to the onset of farming (though not in Ireland).
DNA evidence indicates that much of the human resettlement of western Europe after the last Ice Age originated from Iberia from around 12,000 years ago. The earliest evidence of human occupation in Ireland dates back around 10,000 years ago. Although sea levels were much lower than they are today, Ireland may already have been an island by the time the first settlers arrived by boat. Most of the Mesolithic sites in Ireland are coastal settlements and the earliest inhabitants depended for much of their livelihood upon the sea.
The snail DNA findings provide further evidence of an established Mesolithic trade route between the Iberian ancestral homeland and their cousins in Ireland. It is curious that the snail DNA markers were found some 60 miles inland in the Pyrenees and not on the Atlantic coast of Spain or France. One explanation is that the Garonne river, which runs from the Pyrenees, through southern France, past Toulouse and up to the Atlantic coast at Bordeaux, has long been a principal route between the Mediterranean and the Atlantic. The presence of the snails in Ireland might be a long lasting consequence of this ancient transport route.
Angus Davison said: “It’s interesting to use snail genetics to find out how snails colonise, and it also maybe gives us a little insight into what humans were doing, too. One really neat thing about this study is that, if we accept that humans transported snails, it really gives us a unique insight into an individual journey 8000 years ago, and it gives us evidence of that from a source you might not imagine.”