The period between the start of the Iron Age and the historic period (431 AD) saw the gradual infiltration of small groups of Celtic-speaking people into Ireland,[7][8] with items of the continental Celtic La Tene style being found in at least the northern part of the island by about 300 BC.[9][10] The result of a gradual blending of Celtic and indigenous cultures would result in the emergence of Gaelic culture by the fifth century.[7][11] It is also during the fifth century that the main over-kingdoms of In Tuisceart, Airgialla, Ulaid, Mide, Laigin, Mumhain, Cóiced Ol nEchmacht began to emerge (see Kingdoms of ancient Ireland). Within these kingdoms a rich culture flourished. The society of these kingdoms was dominated by an upper class consisting of aristocratic warriors and learned people, which possibly included Druids.