 Essentially a variant of the earldom hypothesis, there is little archaeological evidence in its favour, although it is clear that extensive Viking incursions on the Irish coasts were supported by a presence of some kind in the Hebrides, even if the date the latter became prominent is far from certain.As Ó Corráin himself admits "when and how the Vikings conquered and occupied the Isles is unknown, perhaps unknowable".Norse contacts with Scotland certainly predate the first written records in the 8th century, although their nature and frequency are unknown.