There were, in Europe and beyond, peoples who were known as Celts, whose movements and behaviour are reflected in contemporary sources. They spoke a language which spread over a huge area, versions of which are still spoken and taught today in the western fringes of the former territory. Some of these ancient Celtic communities developed a unique art and a distinctive material culture, which spread thoughout Europe, and in the remote west, in Ireland, echoes of their society come down to us through the written versions of a long-extinct oral tradition.
Celtic belongs to the family of Indo-European languages. On one extreme it has been suggested that the main Celtic-speaking groups were in place as early as 3000 BC, but the more conventional view accepts that Celtic developed in the regions in which the Celts were to flourish during the period of 1300-800 BC. Celtic languages originally extended in a broad swath from south-western Iberia (Spain), through Gaul (France) and the Alpine region, into the Middle Danube, and one group of Celtic settlers, the Galatians, introduced Celtic into central Asia Minor where it as said to be recognizable in the fourth century AD.
Of the recognized Celtic languages, Celtiberian was spoken in Iberia with the earliest inscriptions dating to the third century BC with suggestion that the language was there at least two centuries earlier. The Gaulish language was spoken extensively in Gaul in the first century BC. The Lepontic language was spoken south of the Alps in the northwestern Po Valley (northern Italy) with inscriptions that are said to date to the sixth century BC. Little is known of the Celtic spoken in the Middle Danube Valley, a general area that has been rich in the Celtic archaeological study of the Hallstat and La Tene periods.
For the Celtic languages spoken in Great Britain, Ireland, and Brittany (northwestern France), it is conventional to divide them into two groups: Q-Celtic, or Goedelic, spoken in Ireland, the Isle of Man, and western Scotland, and P-Celtic, or Brythonic, which forms the basis of modern Welsh, Cornish, and Breton. The long-established belief has been tha Q-Celtic was the older form with a strong possibility that the language was spoken in Ireland, as well as other areas, as early as the sixth century BC.
It was during the late Bronze Age, roughly 1300-750 BC, that the Celtic language developed its recognizable characteristics in western Europe. By 600 BC "Celtic" was said to be spoken in Iberia, Ireland, and around the Italian Lakes, and it is reasonable to assume that it was also in use over much, but not all, of the intervening area. Although a matter of debate it is consistent with the archaeological evidence that the origin of Celtic lay within the Rhine-Danube zone late in the second or early in the first millennium.
From c.750 to c.450 BC two recognizable elite Celtic cultural areas are indicated in the archaeological record in the Rhine-Danube (West Hallstat) zone and in the Meseta of Iberia (north-central Spain). It has been suggested that the developing divergence of P-Celtic and Q-Celtic may have begun during this time.
From c.450 to 200 BC the distinctive La Tene material culture had developed around the northern and western fringes of the West Hallstat zone. It was during this time that migrations began into the Mediterranean and east European zones. La Tene materials have been found by archaeologists in Ireland.
Up to 200 BC the tranformation of the Celtic world was gradual and uneven. In the century and a half that followed the Celtic communities of continental Europe were completely overrun from a rapid escalation in the Roman desire for empire, from Germanic pressures from the Nordic zone, and from Dacian and Sarmatian pressures from the east European zone. By 400 AD the surviving celtic languages were mainly limited to the areas of Ireland, Scotland, Wales, Cornwall and Brittany.