The early Bronze Age culture is commonly believed to have grown out of Beaker roots, with some Wessex and Unetice influence. In the early Bronze Age, rich individual graves are found under barrows, which indicates a complete change of the social structure. The Breton barrows have been divided into two series by Cogné and Guiot, the first dating from 1900-1600 bc, the second to 1600-1400 bc. The barrows of the first series can be up to 50 m in diameter and 6 m high. They are found in Western Brittany, along the coast, the Blavet river and at the southern border of the Monts d'Arrée. A few examples have been recorded from Normandy. The barrows contain a small cairn over a stone cist, wooden coffin or dry stone structure containing the burial. Often the chambers are covered by large stone slabs. Sometimes roofed mortuary houses are found, for example at St. Jude en Bourbriac. The stone cists can be quite large, up to 4 m long, but always only contain a single body. Grave gifts include amber beads, silver cups, gold-hilted daggers (Saint Adrien), tanged flint arrowheads and stone axes. Because of these rich grave goods, J. Briard sees them as burials of warrior-priests. Certainly not everybody was buried in this way, but nothing is known of "commoner-burials", especially as bones are not normally preserved in the acidic soils of Brittany. The gold-pin decoration of the dagger hilts and the amber-beads show close connection to the Wessex-culture, but there are technical differences.