The development of the complex drystone architecture of the Atlantic has seen exensive discussion (see theme 5.9). The role of maritime links is of prime and indisputable importance here, enabling the transmission of knowledge and architectural preferences within social contexts that remain uncertain. This whole area remains one of active debate.
Edins Hall, Scottish Borders © RCAHMS
The adoption of exotic architecture has often been seen as an indication of construction and use by high-status occupants. The so-called 'southern brochs' are an excellent example of this - Macinnes' model of a network of high-status sites with occupants controlling a prestige goods economy associated with the redistribution of Roman goods is still widely accepted (Macinnes 1984). More could be done on the background to this phenomenon - there are other stone houses in the southern Scottish Iron Age, often termed duns (e.g. Stanhope (Peeblesshire), Castlehaven (Kirkcudbrightshire), Castlehill Wood (Stirlingshire); RCAHMS 1967, 157-8; Barbour 1907; RCAHMS 1963, 81). How do these fit into the model of exotic influence? And how many more such brochs can be anticipated? The Buchlyvie broch was an unprepossessing mound before excavation (Main 1998), while the recently-discovered broch at Castle Craig, Auchterarder gave no hint of any surface presence (DES 2011, 144-5). Are all southern brochs similar, or should the Galloway ones be seen as an integral part of the Atlantic world, rather than an introduced innovation (Henderson 2007a , 165-66; Cavers 2008, 16-17)? And do they all date to the Roman Iron Age? The lack of Roman finds from some extensively-excavated examples (e.g. Edin's Hall; Dunwell 1999) raises questions over the suggested tight, Roman Iron Age chronology.
Whitslade roundhouse and souterrain, Scottish Borders © RCAHMS
Other architectural styles or concept are widespread in space and time. Souterrains vary in date from the Late Bronze Age/Early Iron Age in the Northern Isles to the Roman Iron Age south of the Forth, with a presumed floruit in the last centuries BC and first two centuries AD (Armit 1999; Miket 2002). There are differences in construction and dating across the areas of occurrence, but similarities in conception, situation and material assemblages imply links in terms of their function and behaviour. Composite ritual and storage functions (Henderson 2007a , 142-7) have been argued although such a composite functional interpretation may not be sustainable for all areas (see Dunwell & Ralston 2008 on Angus souterrains versus Carruthers on Orcadian examples).
Ring-ditch houses may be a further example of longevity accompanied by gradual transfer over territory. They appear to be present for up to a millennium north of the Tay before they are documented south of the Forth, (although there is the possibility of a visibility or research bias here, and the nature of the ring-ditch and its formation remains a key question; see theme 4.2). A parallel issue is the re-use or re-invention of crannogs across much of the first millennia BC and AD (and into the medieval period).
It is also clear that the movement of these different building traditions was accompanied by the independent growth of local 'sub-styles' wherever they passed. There are good examples of local distinctiveness within these architectural 'streams'. For example, wheelhouses in Shetland can be argued to be distinct in design from those in the Western Isles (Harding 2009 , 112-4). In turn both areas are quite distinct from Orkney, where classic wheelhouses are absent, but where there are buildings with radial partitions (e.g. at Howmae), suggesting that wheelhouse traits did penetrate the archipelago and so the total distinction drawn may be overemphasised (Harding 2006 , 74; Henderson 2007a , 160). At Scatness in Shetland wheelhouse use extends into the second half of 1st millennium AD, albeit with significant structural differences to earlier forms (Dockrill 2003, Dockrill et al. 2010).
Complex Atlantic roundhouses on Barra and North Uist are also considered distinct from their counterparts on South Uist (Armit 1997 a & b, 2002; Sharples and Parker Pearson 1997). These arguably represent local variations (perhaps autonomous or hierarchical) among the societies of the Western Isles that adopted Atlantic roundhouse architecture. The Atlantic roundhouse need not have resulted from a homogenous cultural background or social structure (Romankiewicz 2011).
- The mechanisms behind the spread of these phenomena remain hotly debated.
- Are the Galloway brochs late 'bastard forms' (Cowley 2000, 174) or part of the Atlantic mainstream (Henderson 2007a, 165-66; Cavers 2008, 16-17)?
- How do lowland brochs fit into their settlement landscapes, especially in relation to other stone architecture?