The association of Mus musculus domesticus with humans in a European context has long been studied by zooarcheologists, and genomic tools are now being deployed to study adaptation in some of these European populations. With regard to colonization history, there is much zooarcheological evidence on the progression of mice from their site of first commensalism with humans in the Near East through the Mediterranean region, providing a good test on the match between mtDNA sequences and the historical record. Gratifyingly, Bonhomme et al. [3] have identified a discontinuity in mtDNA lineages that fits very well with the two phases of mouse colonization of the Mediterranean revealed by zooarcheologists (Figure 1). The eastern Mediterranean was colonized by mice during the Neolithic when they were first able to exploit stored grain. However, the western Mediterranean could not be colonized by house mice until the Iron Age (Figure 1), when settlements reached a sufficient size for the house mice not to be outcompeted by local mice living outdoors, and when seafarers such as the Phoenicians carried cargoes of sufficiently large size to inadvertently transport house mice [3, 4].
Studies by ourselves and others have looked at the mtDNA lineages of house mice in northern Europe. A different lineage from those typically seen in Mediterranean Europe has been found further north in the area between Britain and Germany [2, 5]. The mouse mtDNA again matches a regional sphere of influence of Iron Age people [6], and, unlike other mouse mtDNA lineages, it appears that this Anglo-German lineage did not arrive in northern Europe by an overland route; instead it probably came along the Atlantic coast (Figure 1).
mtDNA studies suggest another pulse of detectable mouse colonizations during Viking times (Figure 1). Like the Phoenicians, the Vikings were impressive seafarers, carrying substantial cargoes ideal for stowaway mice, and there are mtDNA signals of maritime colonization events [2, 5, 7, 8].
How did Mus musculus domesticus get from Europe to Kerguelen? This subspecies had been in the right place at the right time to make use of the first storage of grain by Neolithic humans in the Fertile Crescent in the Middle East, and to adapt to changing human cultural practices. Good fortune struck again when the subspecies found itself in western Europe at the time that British, Dutch, French and Iberian seafarers were 'discovering', exploiting and taking settlers to the rest of the world. Kerguelen-Trémarec and his crew may have been the first humans to see the archipelago that now bears his name, but the colonization route of the first mice to arrive there is still uncertain, although their starting point was certainly western Europe (Figure 1).