 The Urnfield period saw a dramatic increase in population in the region, probably due to innovations in technology and agriculture.The spread of iron-working led to the development of the Hallstatt culture directly from the Urnfield (c. 700 to 500 BC).Proto-Celtic, the latest common ancestor of all known Celtic languages, is considered by this school of thought to have been spoken at the time of the late Urnfield or early Hallstatt cultures, in the early 1st millennium BC.