Human migrations throughout history have often been accompanied by species such as the common house mouse, attracted by stores of foodstuffs such as grain required to undertake long journeys and weeks at sea. DNA from how these species then spread alongside human settlements when landfall was made.
A genetic study of ancient and modern mouse DNA, published by BMC Evolutionary Biology, has revealed how they were carried on Viking longboats from Norway or the northern British Isles to colonies in Iceland and Greenland in the 10th century.
Scientists analysed the mitochondrial DNA of modern mice and ancient samples from mouse bones found at archaeological sites. Samples of house mouse DNA were collected from sites in Iceland, Greenland, and L’Anse aux Meadows in Newfoundland, where Vikings are known to have briefly settled.
The descendants of Norse mice can still be found in Iceland and, like its human population, the modern population of Icelandic mice has a very low genetic diversity, indicating a small initial founding population.
Those in Greenlandfared less well and were replaced by Danish mice in subsequent waves of migration from Europe.
Interestingly, no trace of their DNA was found in Newfoundland. If mice did accompany intrepid Viking explorers there, their presence was also fleeting and left no genetic evidence behind. It is possible that the nomadic life style of the indigenous Native American tribes (known to the Vikings as the ‘Skraelings’) did not encourage colonisation by the domestic mouse. The modern-day mouse population in Newfoundland is mainly descended from an English mouse lineage, which probably arrived from the port of Bristol with explorer John Cabot and his crew in 1497.