There is a long history of enclosing ‘forts‘ and settlements from the late second to early first millennium BC into the middle and later first millennium AD. It is difficult to establish any particular floreunt within this timescale (Hingley 1992, 19), although there does appear to have been a significant lull, if not certainly a hiatus, in the early centuries AD. Some sites display activity over a long period, although not necessarily (and probably not) continuously. More dating evidence is required, as there is no real chronological control in any part of Scotland, beyond a sketchy outline in East Lothian and Aberdeenshire. It is therefore difficult to trace the development, character or meaning of enclosure over time at either national or regional level.
Origins / early enclosures
Some of the larger earthwork ‘forts‘ (Traprain Law, East Lothian Armit et al. 2002; Eildon Hill North, Roxburghs. Rideout et al. 1992; Dunagoil, Bute Harding 2004, 141; Ben Griam Beg, Sutherland, Mercer 1991; Ralston 2006, 172-3) have been speculatively dated to the Late Bronze Age, but without unequivocal confirmation from excavation. They have been regarded as part of a pattern of large hilltop enclosures across Britain (e.g. Armit 1997c, 54) although others (Ralston and Ashmore 2007) have hesitated to place these large early sites within a single chronological horizon since some sites (e.g. Burnswark, Dumfries Jobey 1978) appear to have later origins. Arguably more securely dated to the Late Bronze Age are smaller promontory forts (Cullykhan, Banffshire; Gob Eirer, Isle of Lewis) and some curvilinear enclosure recently examined in East Lothian (Haselgrove 2009; but see Sharples 2011). Whether the potentially widespread adoption of enclosure in East Lothian (Haselgrove 2009, 115) was typical of other areas of Scotland or was a precocious development is therefore an interesting question. East Lothian is one of the more intensively investigated parts of Scotland, so this may reflect sample bias or represent a real difference (c.f. Cowley 2009, 222)?
Early to mid first millennium BC
A wide range of palisaded and earthwork enclosures was erected during the first half of the first millennium BC, although close dating has been precluded by the 800-400 cal BC radiocarbon calibration issue (Ralston and Ashmore 2007). Harding (2004, 66-7) argues that the repeated association of palisaded enclosures with ring-ditch houses and cord rig traces in southern Scotland represents a mid first millennium BC phenomenon. These palisaded enclosures are often seen as a kind of ‘pioneer‘ settlement utilising cleared woodland in its construction. Some palisaded enclosures later developed into settlements defined by earthworks. Whilst generally interpreted as settlements bounded by fences, their potential appearance as fortified stockades has recently been reasserted (Halliday and Ralston 2010), especially in relation to the possibility that ‘double palisades‘ may have been box ramparts. The extent of early palisaded enclosures is still to be determined due to potential issues of visibility in the north and west, although there are at least some in the cropmark record outwith south east Scotland.
Later first millennium BC
In this period there would appear to be less emphasis on major hillfort earthwork construction, and it is widely believed that by the end of the millennium a high proportion of forts had fallen out of use. Armit (1997c, 64-5) cited a 20% occupancy of forts on the eve of the Roman invasion and dating evidence from a number of excavations can be adduced to support this (e.g. Broxmouth, Hill 1982a; Brown Caterthun, Dunwell and Strachan 2007; Balloch Hill, Peltenburg 1982). At many sites in southern Scotland where earthworks are overlain by unenclosed settlements, the ‘abandonment‘ of enclosure is generally assumed to have occurred before the Roman invasions (Hill 1982a; Haselgrove 2009), and is not now considered a result of pax Romana. The formation and modification of enclosed settlements continued, This period was the probable context for the appearance of rectilinear enclosures (palisaded and banked) across much of southern and eastern Scotland. Further dating of ‘open‘ settlements overlying enclosing works is required.
Early first millennium AD
Some forts and enclosed settlements were demonstrably being occupied into the first two or three centuries of the first millennium AD (e.g. Castle O‘er and Bailiehill, Dumfries, RCAHMS 1997). Renewed occupation of varying scale at large forts in southern Scotland after putative periods of abandonment or a different type of use has been identified – e.g. at Burnswark, Dumfries Eildon Hill North, Roxburghshire and Traprain Law East Lothian- in some cases posited as ‘boom towns‘ (Armit et al. 2002). By the 3rd or 4th century AD few enclosed places were still in demonstrable use – Traprain Law being a notable exception as evidenced by the construction of the Cruden Wall, probably in the fourth or fifth century AD (Close-Brooks 1983).
Mid to later first millennium AD
In this period there was a new wave of building forts, primarily between the 5th to 9th centuries AD (Alcock 2003, 190). Those with a distinctive morphology are the royal or princely ‘nuclear forts‘ (ibid), some located on earlier fortified sites (e.g. Dunadd, Lane and Campbell 2000) some apparently de novo (e.g. Dundurn, Perths. Alcock et al. 2000). They probably developed by accretion over several centuries, but with different organising principles to those evident in pre-Roman Iron Age forts (Harding 2004, 207) – although some have suggested that The Dunion, Roxburghs. may be an Iron Age precursor of the form (Rideout et al. 1992, 117). Other new Early Medieval forts are more akin to Iron Age precursors in appearance, notably Mote of Mark, Kirkcudbright and Clatchard Craig, Fife (Laing and Longley 2006; Close Brooks 1986, although Harding (2004, 233) suggests an Iron Age origin for its outer enclosure).
There was also ‘refortification‘ of earlier promontory sites (e.g. on the Moray Firth littoral including Cullykhan, Banffs.) and reuse of earlier sites with no demonstrable rebuilding (e.g. Craig Phadrig, Inverness. Harding 2004, 89-90), but all after a break in activity. There are acknowledged difficulties in distinguishing Early Medieval constructions and modifications of Iron Age antecedents within the survey dataset (e.g. Ralston 2004, 2007).
Good dating evidence is an issue across the board. Recent ‘key-hole’ work eg in Strathdon (Cook 2010) offers the prospect of obtaining at least an outline chronology in an area relatively quickly, if stratigraphically-secure material can be identified. Such approaches will inevitably simplify each site sequence, being focussed only on enclosure phases, and need to be followed by more extensive excavations on key sites to develop the picture.