The traditional narrative of Scottish history, is that the kingdom of Dál Riata was founded by Gaels from Ulster in Ireland, who crossed the Irish Sea after being squeezed by the ascent of Conn Cétchathach's descendants (a kindred, but competing line).
This position is upheld in medieval Gaelic texts such as the Duan Albanach, which attributes to the a descent from Síl Conairi of the Érainn.
This is held to be the means by which the Gaelic language came to northern Britain and where the clans who founded Scotland (i.e. - the MacAlpines) first entered the region.
Campbell authored a paper in 2001, named Were the Scots Irish?, in the journal Antiquity, which challenged the relationship between the Gaels of Ireland and those of Dál Riata.
[4] Campbell suggests that Argyll and Antrim formed a "maritime province", united by the sea and isolated from the rest of Scotland by the mountainous ridge called the Druim Alban.