New excavation and analysis of three crannogs – or man-made islands – in the Outer Hebrides has clearly demonstrated that they had Neolithic origins, changing our understanding of these enigmatic sites.
There are over 570 crannogs found in lochs and inlets across Scotland, with over 170 in the Outer Hebrides alone (numerous crannogs are also located in Ireland as well as one in Wales). Previously, it had been thought that they were built, used, and reused over a period of 2,500 years, stretching from the Iron Age through to the post-medieval period. Then, in the 1980s, excavation at Eilean Dòmhnuill in North Uist revealed that this particular islet was actually constructed during the Neolithic. Despite this tantalising discovery, no other Neolithic crannogs were revealed in the subsequent decades of searching.
Then, in 2012, Chris Murray, a resident of the Isle of Lewis and a former Royal Navy diver, was diving around one islet and discovered Neolithic-style pots lying on the loch bed. Joining up with Mark Elliott from the Museum nan Eilean in Stornoway, they then searched around several other islets on the Isle of Lewis, finding similarly well-preserved collections of Neolithic pottery.
To confirm whether these watery deposits were linked with the crannogs’ construction, Duncan Garrow from the University of Reading and Fraser Sturt from the University of Southampton conducted an extensive survey of three of them: those in Loch Arnish, Loch Bhorgastail, and Loch Langabhat. Using several different techniques, Duncan and Fraser aimed to identify how these islets were built, when they were built, and for what purpose.
Preliminary findings from this project were presented by Duncan and Fraser at CA Live! 2018 and in CA 325, but after completing their full analysis of the sites they found some interesting features. Both the Bhorgastail and Langabhat islets were built on natural rises in the loch, and in the Neolithic they would have been surrounded by shallow water on three ‘sides’, with deeper water on the fourth. To stabilise the boulder-built structure on the deeper side, it was discovered that at Bhorgastail timbers were used to revet the edges of the islet.
In addition, Duncan and Fraser determined that the vast amounts of pottery found around Bhorgastail and Langabhat were probably purposefully deposited directly into the water surrounding the islet, supporting the idea that these sites were used during the Neolithic. To confirm this, radiocarbon dating was used on charred residue from inside the pots found at each of the three crannogs, as well as on the wood revetments from Bhorgastail. The results confirmed that all three islets were indeed used within a narrow timeframe during the Neolithic: 3640-3360 BC.
While the exact reason for their construction is still a bit of a mystery, overall this project has demonstrated that crannog-building may have been a fairly widespread practice during the Neolithic, at least in the Outer Hebrides. More work on crannogs throughout Scotland and Ireland would help establish whether this was a practice that spread further afield as well.
The Antiquity paper outlining these findings can be read for free from https://doi.org/10.15184/aqy.2019.41.