History of the Outer Hebrides
The Hebrides were settled early on in the settlement of the British Isles, perhaps as early as the Mesolithic era, around 8500–8250 BC, after the climatic conditions improved enough to sustain human settlement. There are examples of structures possibly dating from up to 3000 BC, the finest example being the standing stones at Callanish, but some archaeologists date the site as Bronze Age.
Source: Wikipedia — History of the Outer Hebrides (CC BY-SA 4.0)