Prehistoric man brought Ireland its tiny shrew
Submitted by Baz on Tuesday, 30 December 2003 Page Views: 17791
EnvironmentIrelnd's smallest mammal, the pygmy shrew, originated in Andorra, scientists believe. A genetic study indicates that the tiny animal — about half the size of a mouse — was introduced to Ireland by humans from southwest Europe in the Mesolithic.The creature probably arrived here as an accidental passenger on boats and not from Britain by means of natural colonisation, as previously thought.
The finding supports the theory that many of Ireland’s animals were originally transported here by prehistoric man. It is also the latest research to show a genetic link between northern Spain and Ireland.
Biologists at the University of York conducted a genetic study of the species, comparing specimens from Ireland, Britain, and the continent as far east as Turkey and Russia. It found the Irish pygmy shrews were nothing like British and other northern Europe specimens but were closely related to those in Andorra, a tiny principality in the Pyrenees between France and Spain.
“During the process of human colonization of Ireland in the Mesolithic (part of the Stone Age), or as a result of subsequent trading links, humans could have accidentally or deliberately transported a variety of species between these two areas,” the report concluded. “The findings would clearly be of great interest to archaeologists as the continental source area of Irish pygmy shrews may also represent the continental source area of Irish people or at least somewhere from where people embarked to trade with Ireland.”
Silvia Mascheretti, one of the authors of the study published in Proceedings: Biological Sciences, said: “There was a rather unexpected finding that the animals in Ireland were related to individuals from Andorra.
“This similarity suggests that the colonisation was through humans, probably by boat. Very few individuals survived this journey by boat which explains the great similarity of all the Irish individuals.”
At around 60mm in length, the pygmy shrew is Ireland’s smallest land mammal. It has very poor eyesight, hunting by smell and touch. Because of its high metabolic activity, it must eat at least its own body weight in food each day. Unlike in Britain, it is the only species of shrew found in Ireland.
It has been a long-standing mystery how Ireland got its present fauna after the last ice age. Few mammals, if any, survived the glaciation event when Ireland was under about a kilometre of ice. One theory was that they arrived via a land bridge which may have briefly existed between Ireland and Britain.
The study has ruled out this method for the pygmy shrew, at least, although biologists believe other species may also have been imported. “It does start to get to the data that really answers the question as to where Irish mammals came from,” said Dr Tom Hayden, a biologist at University College Dublin.
“This is a crucial question. This allows us to knock the current thinking of where the source population probably was on the head — that it wasn’t actually Britain.”
Hayden, who gathered the specimens of Irish pygmy shrews for the study, said: “The big problem is exactly where Ireland’s mammals came from. We would expect those in Britain to be most like ours, but that doesn’t seem to be leaping off the data at the moment.
“We tend to forget that the sea routes were less daunting at that time. In retrospect, it may not have been such a big deal to have contacts between southern France or northern Spain by the sea route.”
Dr Dan Bradley, a geneticist at Trinity College, Dublin, said the pygmy shrew data tied in with an aspect of his human genetic findings.
“It is a plausible hypothesis that the bulk of our fauna was introduced — that it didn’t walk here but was brought here on boats. It seems to back up the idea that sea routes were important, not necessarily from Britain.”
Source: The Times On-line August 2003
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