A reappraisal of mitochondrial DNA introgression in the Mus musculus musculus/Mus musculus domesticus hybrid zone suggests ancient North-European associations between mice and humans.

The house mouse is the best-studied mammal species after humans, yet our understanding of its evolutionary history remains incomplete. Here, we focused on the colonisation of Europe by two subspecies and formation of a hybrid zone between them. We carried out a large-scale study of ~7000 mice sampled across an area embracing an ~900 km long portion of the zone, supplemented with cytochrome b and D-loop sequencing of ~1200 individuals collected worldwide. We demonstrate that the course of the mtDNA contact front is intricate and highly discordant with the consensus front for autosomal and X-linked markers, suggesting that local snapshots of mtDNA introgression may be misleading when treated in isolation. While multiple unrelated M. m. domesticus haplotypes occur in the zone area, the diversity of M. m. musculus haplotypes is limited. Moreover, we uncovered a vast region of domesticus introgression into musculus territory in northern areas and showed this introgression is unlikely to be driven by positive selection. We consider two previously published hypotheses explaining this phenomenon and put forth an alternative scenario assuming associations between mice and humans in northern Europe during the Nordic Bronze Age and subsequent zone movement associated with the expansion of Balto-Slavic peoples. [ABSTRACT FROM AUTHOR]