If carrying insects and small animals on board is commonplace today, could it have been different in the past — ten to 12 centuries ago? Not so, going by the evidence provided in a paper published recently in the journal BMC Evolutionary Biology. The paper provides an interesting find that rodents carried by the Vikings, the Scandinavian people who raided much of Northern and Western Europe from 8 to 10 century, left behind a genetic trail.
Looking at the trail the study concludes that mice distribution in Iceland, Greenland and Newfoundland parallels the human explorations of these areas. They were able to confirm this by comparing the DNA of modern mice population with the DNA obtained from archaeological material like bones from these places.
To understand the spread of mice populations, the study considers two sub species of common house mice. One is the Mus musculus , found in Sweden, Poland and Denmark, while the other is Mus domesticus , members of which are common in Norway, UK, Ireland, France and Germany.
In addition to studying the Mitochondrial DNA (the DNA that is present outside the nucleus in a cell), the authors have used four nuclear genetic markers to differentiate between the two subspecies.
In the case of Iceland, the DNA of both modern and ancient mice matches the sub species Mus domesticus . This shows that the population that initially reached the island survives till date. “In Iceland, the [mitochondrial DNA] data show the arrival and continuity of the house mouse population to the present day,” they write.
The modern mice of Newfoundland too, belong to the same subspecies as that of Iceland. But whether the Vikings carried the early mice to Newfoundland is not known due to lack of DNA material of early mice.
Greenland tells a slightly different story. While the DNA from ancient mice bones here belong to the same sub-species as Iceland, the modern mice that populate this area belong to Mus. musculus . This suggests that the initial population that came to Greenland went extinct.
( The author is a freelancer based in Chennai>madhav.vishnubhatta@gmail.com )
