When people first started to sow and reap cereals in the fertile plains of the Middle East about 10,000 years ago, wild mice quickly seized on this new and plentiful food source and moved into the farmers' fields and grain stores. As human communities expanded, mice took up residence in their dwellings, sharing their food and benefiting from the shelter of their walls and roofs. So the wild mouse became the familiar house mouse, following humans wherever they set up home and adapting to various new surroundings, from polar climes to coalmine shafts. Hidden in packing cases, personal belongings or food stores, the mice were transported across Europe and from there on trading ships to the rest of the world. The house mouse is a fast and prolific breeder and where the climate is mild and food plentiful, it can rapidly reach plague proportions: in the USA during 1941-2 , biologists recorded some 82000 house mice per acre (o.4 ha).
Over the years, some groups of modern house mice have developed special characteristics that help them to survive in their new environments. Long-term residents of refrigerated cold stores, for example, have grown much thicker fur to protect themselves against the permanently freezing temperatures of their homes.
