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In page Celts:

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The mainstream view during most of the twentieth century is that the Celts and the proto-Celtic language arose out of the Urnfield culture of central Europe around 1000 BC, spreading westward and southward over the following few hundred years.[1][2][3][4] The Urnfield culture was preeminent in central Europe during the late Bronze Age, circa 1200 BC to 700 BC. The spread of iron-working led to the Hallstatt culture (c. 800 to 500 BC) developing out of the Urnfield culture in a wide region north of the Alps. The Hallstatt culture developed into the La Tène culture from about 450 BC, which came to be identified with Celtic art.[citation needed]