In Europe, the Iron Age may be defined as including the last stages of the prehistoric period and the first of the proto-historic periods.Iron working was introduced to Europe in the late 11th century BC, probably from the Caucasus, and slowly spread northwards and westwards over the succeeding 500 years. The widespread use of the technology of iron was implemented in Europe simultaneously with Asia. There is not a clear consensus on how the end of the Iron Age should be defined (see Three-age system § End of the Iron Age).