Mesolithic Human Travelers Brought Snails To Ireland
June 20, 2013

Mesolithic Human Travelers Brought Snails To Ireland

Brett Smith for - Your Universe Online

Previous studies have suggested that the islands of Great Britain and Northern Ireland began to separate from the European mainland around 10,000 years ago, with a massive tsunami completing the process about 8,000 years ago. Any land animals to naturally migrate to the two islands would have to have made the trip before this separation.

With this set of circumstances in mind, scientists have long wondered why Ireland has some plants and animals that are so genetically different compared to those found in Britain. One of these Irish species, a common garden snail, is genetically identical to specimens found near Europe´s Pyrenees Mountains and was likely brought to Ireland by human travelers, according to a new study in the open-access journal PLoS ONE.

Study researchers performed a fossil analysis that showed a continuous record for these snails in Ireland over the past 8,000 years and evidence collected from the Pyrenees region of France showed that the mollusk was a snack thousands of years ago.

The research team also performed a genetic analysis on nearly 900 snails from both regions. They focused on mitochondrial DNA, which is passed directly from mother to child, and genomic segments that are known to vary from species to species.

The researchers said it was difficult to explain how the genetically identical snails could be present in Ireland and France but not in Great Britain.

"There are records of Mesolithic or Stone Age humans eating snails in the Pyrenees, and perhaps even farming them," said co-author Angus Davison from the University of Nottingham´s School of Biology.

"If the snails naturally colonized Ireland, you would expect to find some of the same genetic type in other areas of Europe, especially Britain,” Davison said. “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,” he continued. “What we're actually seeing might be the long lasting legacy of snails that hitched a ride as humans traveled 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," Davison said.

Dan Bradley from Trinity College Dublin told BBC News that the study reinforced the notion that some species in Ireland are genetically similar to those in southern Europe, yet not found in Britain.

"It's consistent with the idea that almost everything we have in Ireland, that can't swim or fly, was brought here on a boat,” said Bradley, a population geneticist.

Previous genetic research has also shown links between the human population of Ireland and those in Southern Europe.

"The genetic patterns in humans are there, but are much weaker,” Bradley said. “You see it in blood groups, in Y chromosomes and some diseases.”

"In order to really understand migration patterns we need more ancient DNA from different species such as small mammals," he added.