New insights into the invasive process of the eastern house mouse (Mus musculus musculus): evidence from the burnt houses of Chalcolithic Romania

The house mouse invasion of the European continent has crucial implications for our understanding of the synanthropization process of European small mammals during the Holocene. Mice remains collected from a Chalcolithic burnt house in southern Romania, provided a unique opportunity to document which of the two house mouse subspecies was the commensal taxa of the late Neolithic Romania and question the factors of its invasive process. To obtain the subspecific status of the Mus remains, we performed molar shape analysis with geometric morphometrics, using 160 specimens sampling the extant Eastern European Mus taxa as modern comparatives. Along with an overwhelming majority of eastern house mice (Mus musculus musculus) living constantly in the Chalcolithic house, indigenous small mammals (common hamster, field mice, voles and white toothed shrews) were also occupying the settlement sporadically, highlighting the antiquity of the synanthropisation of European small mammals. This secured occurrence of the eastern house mouse in late Neolithic Romania, led us to propose two testable research hypotheses: first, an eastern house mouse commensalism center in Eastern Europe happening during the sixth millennium BC, when neolithization reached the natural distribution of free living populations of Mus musculus musculus in the Pontic steppes of Ukraine; second, new trajectories of trading networks, stimulated by copper metallurgy around the fifth millennium BC, having allowed long-distance translocation of the commensal eastern house mouse from Eastern to Southern Europe Neolithic settlements.