The tradition of building fixed boundaries to demarcate holdings or estates in the Scottish landscape is a relatively recent phenomenon, and was only put in place over the greater part of the country with the agricultural improvements of the late 18th and 19th centuries. Before this, the sense of territory and rights to use areas of land was no less defined, but was regularly refreshed by the beating of the bounds, a practice which is sometimes preserved in the detail of medieval charters describing a perambulation along the course of a boundary and the markers that were used to fix it in the landscape. Typically a boundary might run simply where ‘wind and water sheer‘, but prominent outcrops and summits played their parts, along with occasional trees and boulders, or an ancient standing stone or cairn. In places small piles of stones might be employed, or pits and stakes. By these means the mosaic of ownership, tenure and rights interlocked across the medieval landscape to cover all its resources, from the sea to the very tops of the mountains, including everything from fish and fowl to bog, pasture and forest. Such boundaries were often a matter of interpretation, as estate maps on the eve of the Improvements sometimes show, recording several versions of the same march as identified by different individuals. And it is such differences in interpretations and the disputes that arose from them that provide the most detailed knowledge about the marches of medieval holdings. Since the synthesis of shires and thanages by Professor Geoffrey Barrow (1973), it has been clear that components of the high medieval landscape were firmly rooted in the early medieval landscape, a period that in some parts of Scotland is included in the long Iron Age. The work in Moray by Alisdair Ross on another type of land division, the dabhach, has shown that this too is an early medieval measure that divided the landscape to provide estates with all the necessary resources of arable, pasture, peat and woodlands.
Such a division, it might be argued, is likely to be the product of centralised authority with the power to implement sweeping reform at a scale in the landscape that would not be surpassed until the 18th century. As such, there is a temptation to assign it to periods when there are named figures who might have exercised such power. Equally, however, its origins may lie earlier in the Roman Iron Age when there was evidently extensive reorganisation of settlement across a wide sweep of eastern Scotland at the end of the 2nd century AD. At the very least it should be expected that the Iron Age landscape was divided in comparable ways, even if it varied in scope and detail. And at whatever date this reformation may have taken place, it is more than likely that in most places the rights to recognisable units of land were being exchanged or altered within an already settled landscape pattern, rather than a situation where surveyors were being employed to redefine the holdings and rights on an entirely blank canvas without reference to what had gone before. In short, the study of medieval and post-medieval documentation not only provides a constructive approach into examining the landscape that emerged from the Roman Iron Age, but may also have fossilised elements of earlier landscape boundaries, from political divisions at one extreme to individual holdings at the other.
The challenges of using such data in any Iron Age reconstruction are considerable, if only because without documentation the majority of such boundaries would probably be unrecognisable. This is further compounded in those areas where there is evidence that boundary works were erected during the Iron Age, that none of them is enshrined in the march of a documented medieval estate, although the Thorneybank long cist cemetery in Midlothian lies immediately adjacent to an earlier linear earthwork flanked by a row of pits (Rees 2002). Nevertheless, a study of the distribution of Pictish symbol stones in the Aberdeenshire landscape has explored the possibilities of making comparisons between their distribution and the pattern of medieval parishes (Fraser and Halliday 2007; 2010), and while it is clear that the stones do not stand directly on these ostensibly later boundaries, the correlation of their proximity is remarkable. The extension of the argument to embrace early medieval barrow cemeteries to the north of the Forth and long cist cemeteries to the south, and then a more limited selection of Iron Age burials, has thrown up further correlations that at least require research to develop some level of explanation. Artefact distributions, such as hoards and other metalwork, would also be worth considering in this light.
The linear earthwork discovered at Thorneybank is characteristic of a type of boundary that has been discovered widely in Lothian and the Borders, both through fieldwork in the uplands and aerial photography in the lowlands. While the majority of those in the uplands, mainly of Roxburgh, are flanked by ditches, many of their lowland equivalents are simply marked by lines of pits. With a few notable exceptions these are known only through cropmarkings and are thus limited to the principal areas where cereals are grown in Berwickshire and East Lothian. When the first rash of examples were discovered in the late 1970s, it was anticipated that the whole landscape was divided up in this way, but now, thirty years later, there are still large gaps in the distribution and data collection and analysis has been sufficiently rigorous that it can be confidently asserted that such an all-encompassing land division was not the case, though such boundaries in eastern Berwickshire occur over a distance of several kilometres along Bunkle Edge and around Chirnside. By and large, pit-alignments, as these curious boundaries are known, form localised clusters, in some cases almost certainly forming systems (e.g. at The Chesters, Barney Mains or Eastfield , Inveresk, East Lothian). This is probably the case with the three that survive upstanding in the vicinity of Milkieston Rings, Peeblesshire, and find comparisons with the ditched linear earthworks on White Hill and perhaps Woden Law, in Roxburgh. In several instances in the cropmarks there is simply a single earthwork apparently forming a large enclosure around a fort, such as Huntshaw Hill at the foot of Lauderdale and it is such an enclosure against the crest of a steep escarpment that seems to lie at the core of the system at Barney Mains. The relationship to the forts in these cases, however, is quite unknown and at Killielaw Knowe in eastern Berwickshire there is an extensive system with a rectilinear layout where no evidence of any settlement earthworks have yet been recovered. Nor is there any clear relationship between the system at Eastfield, Inveresk, and any of the various palisaded or ditched enclosures within its compass. Equally unknown is how any of these systems functioned and what they were designed for. Systems where the earthworks lie open on the slopes of a hill, such as at Woden Law, are particularly puzzling.
These systems are not entirely limited to the south-east of the country and are also found on the Solway plain, though not much further west than the River Nith. Of particular note here is the system around Castle O‘er in Eskdale, where the results of trial trenching carried out by Mercer suggest a date in the early centuries AD. While this system is apparently centred on a major fortification in the area, that on Craighousesteads Hill, Dumfries is not, apparently ignoring the circular settlement on the crest of the hill. Other Dumfriesshire settlement enclosures on the Solway Plain, such as Whinnyrig, Calvertsholm and Raeburnfoot, Gretna seem to have been incorporated into systems of earthworks (RCAHMS 1997, 55-7, fig. 52), though at Hayknowes a rectilinear settlement was constructed over one of the boundaries. Unlike their counterparts in the east several of these seem to include long droveways, but other than this possible indication of stock management little is known about their function. The relationship to the annexes of the fort at Castle O‘er, however, perhaps signals that these localised systems of landscape enclosure, both in Dumfriesshire and the eastern Borders, indicate places of importance in the Iron Age landscape, rather than any general importance of enclosure in the Iron Age landscape.
Others of the linear earthworks that occur in the Border hills may have been constructed as markers on the boundaries of larger territories, in particular the short cross-ridge dykes, sometimes in very remote places, but in other instances in the immediate proximity of a prehistoric settlement. An example can be found adjacent to a fort on Wether Hill in Northumberland, though there is no particular reason why it should relate to any period of occupation of the fort. The date is a useful marker in pointing up that this type of earthwork is perhaps more likely to belong in prehistory than in the Middle Ages. Over the years several cross ridge dykes have been interpreted as sectors of much longer boundary works such as The Catrail in Roxburgh, and Heriot‘s Dyke in Berwickshire. By virtue of their discontinuity across the landscape, linking up burns and other natural features, both have been subject to claims and counter-claims by the protagonists of competing theories, but at least one sector of The Catrail seems to be of late Iron Age date (Barber 1999), while in one sector of the earthwork known as the ‘Deil‘s Dyke‘ in Dumfriesshire the core of the bank was dated to the early Iron Age. If these works do indeed hold any long-distance integrity, then they are important monuments about which relatively little is known.