From their onset, the first radiocarbon dates gave a range of the absolute chronology to come, but in their detail, they opened more problems than they settled, chiefly because of the possible or unsuspected questions in relation to the reliability of the samples themselves (Delibrias and Giot, 1970). It is only with the experience of great numbers of dates, and the possibility of considering them so to speak statistically, that one can evaluate the real implications of the time scales provided by the method.
In Brittany, beginning with a few dates provided by the Groningen Laboratory under H. de Vries, we have been afterwards nearly totally supplied by the Centre des Faibles Radioactivités at Gif-sur-Yvette (Giot, 1960, 1961, 1962, 1963, 1965, 1966, 1967, 1968, 1969, 1970, 1971; Coursaget and Le Run, 1968; Delibrias, Guillier and Labeyrie, 1964, 1965, 1966, 1969, 1970; Coppens, Durand and Guillet, 1968; Vogel and Waterbolk, 1963).
We now benefit with more than 200 radiocarbon dates for Brittany alone. We shall consider here about 140 of them, disregarding some duplicates, dates pertaining to periods older than the Neolithic cultures or on the contrary later than the Iron Age, and dates only concerning geological natural sites, though these can be full of interest by their information about the botanical scenery and the effects of cultivation or pasture.