Figure 1

Maps showing possible colonization routes taken by the western house mouse Mus musculus domesticus , based on mtDNA evidence. Neolithic (starting 12,000 years ago): colonization restricted to the eastern Mediterranean close to where this subspecies first became commensal [3]. Iron Age (starting 3,000 years ago): colonization westwards along the Mediterranean and then into north-west Europe by overland and coastal routes [3, 5]. Viking Age (around 1,000 years ago): movements around the periphery of north-west Europe and colonization of Scandinavia and Madeira [2, 5, 7, 8]. (The colonization of Scandinavia may have been earlier [7].) Recent history (a few hundred years ago): mice were taken substantial distances from western Europe, including to Kerguelen [1]. The dashed line shows the location of the hybrid zone between the subspecies M. m. domesticus and M. m. musculus.