The SIRFA resource assessment has identified more than 1000 radiocarbon dates for archaeological material from across the Outer Hebrides. There are likely more out there buried in unpublished reports, or yet to come to light through the planning process. There are also other scientific dating techniques, namely OSL archaeomagnetic dating, thermoluminescence (TL) dating and Optically Stimulated Luminescence dating (OSL). Of these techniques, only the latter two (TL and OSL) have been used extensively across the Outer Hebrides but has been shown to have significant potential, specifically within machair-forming deposits (Kinnaird et al 2019). Nevertheless, the current assessment of c-14 dates highlights some trends that are worth noting in terms of chronology knowledge gaps.
Dates that fall within the Palaeolithic and Mesolithic periods are surprisingly high, almost 16% of the dates in this study. This is especially odd given the very limited dataset for these periods. However, further scrutiny highlights that the vast majority of these early dates are from isolated environmental samples, including peat deposits, loch sediment deposits, offshore marine and continental shelf deposits, with less than 15% of these dates directly associated with anthropogenic activity.
For the Neolithic period, there is a reasonably good geographic spread of radiocarbon dates drawn from a number of early prehistoric settlement sites include Coileagan an Udail (the Udal, Crawford 1977), Eilean Domhnuill (Armit 2003), An Doirlinn (Garrow et al 2017a), vastly expanded with dating outputs from the Neolithic stepping stones project (Garrow et al 2017b; Blankshein et al 2023). Despite this, the overall timeline of Neolithic activity remains poorly resolved, limiting the ability to identify patterns across domestic and monumental sites. More specifically, there is an almost complete lack of independent dates for Neolithic monuments, making it unclear how different structures such as chambered cairns, stone circles, and standing stones relate to one another chronologically. Neolithic pottery, while distinct in style, lacks a formal chronological sequence. The presence of a Chalcolithic phase in the Outer Hebrides remains is uncertain, as current interpretations are based on mainland evidence and there is a lack of secure dating. The region’s Beaker culture appears to have unique characteristics, but again a lack of secure dating inhibits more detailed understanding of Beaker development across the Outer Hebrides.
For the Iron Age, despite a number of large excavation projects and many radiocarbon dates, the dating of brochs and complex roundhouses remains vague, but could be refined through Bayesian analysis of previous excavations. The lack of primary broch phase dates however remains problematic (see also Armit 1991b). For the early historic period, the small site database of known sites is matched by a similarly limited number of radiocarbon dates. Furthermore, of the 103 radiocarbon dates that fall between the 5th and 11th centuries AD, almost 80% derive from just two excavation projects: the SEARCH project excavations at Bornais (Sharples 2019, 2020), and Cille Pheadair (Parker Pearson et al 2018), both in South Uist. Other key chronological questions for this period include the timing of Christian conversion, which currently remains unknown, and the chronological relationship between early Christian sites and pre-existing pagan structures. The earliest Scandinavian contact, and the speed of the transition from Iron Age to Norse culture, also requires further investigation and chronological refinement.
For more information about c-14 dates from the Outer Hebrides, you can download the datasheets for each archaeological period.
Chronology Research Questions
What is the chronological relationship between Neolithic monuments across the Outer Hebrides?
Whilst Neolithic monuments (chambered cairns, standing stones, stone circles) still dominate the Hebridean landscape, there has yet to be a systematic programme for dating these sites. It is currently not known what the interplay or relationship was between the construction of these different monuments, nor if their use represents different periods throughout the Neolithic. A more detailed chronology would provide insight into the construction of different styles and would provide some level of insight into Neolithic Hebridean monumentality.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
What is the chronology of the earliest Christian sites across the Outer Hebrides?
The arrival of Christianity is understood to have originated from Ireland, however, there has thus far been little to no evidence of these early sites found. Can this traditional narrative be further supported with archaeological evidence? Did Christianity in the Hebrides originate from the south, or from the Picts in the east? Building a chronology of early Christian sites will help us to further understand Iron Age connectivity, insularity and social links.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
What is the earliest date associated with brochs or complex roundhouses in the Outer Hebrides?
The chronology of brochs and complex roundhouses is still only vaguely understood in the Outer Hebrides and requires both clarification and more detail. As an initial step, reanalysis of previous large-scale excavations of these sites, particularly those with deep stratigraphy should be undertaken. The use of Bayesian analysis to model these chronologies is recommended. However, the existing broch and complex roundhouse excavations have focused on upper levels and there is currently a lack of secure stratigraphy for initial occupation phases. Therefore, new excavations will be required if researchers are to address this question fully.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
What is the earliest evidence for human habitation or activity in the Outer Hebrides?
There has been no evidence found thus far for Palaeolithic activity among the Outer Hebrides. However, it is not clear whether the lack of evidence is evidence of absence, a result of destruction of Palaeolithic sites in the ensuing centuries, or simply that their character and location are just unclear/unknown so have not been identified yet. The presence of Palaeolithic sites in Skye (Hardy and Ballin 2024) and Islay (Mithen et al 2015) may indicate that they also exist in the Outer Hebrides. This type of evidence is likely to survive in areas not directly impacted by ice sheets, such as caves, gulleys and at the bottoms of protected bays. It is likely that theseis questions will be addressed via a combination of targeted survey and opportunistic discoveries via walk-over surveys, archaeological monitoring or evaluation within a developer-funded context and as a result of coastal erosion. Within a developer-funded context, the research significance of any potential palaeolithic evidence information should be emphasised. The potential for discoveries as a result of offshore developer-funded work is potentially significant. Another approach could be the careful appraisal of existing lithic assemblages, where these exist, with reference to mainland and other west coast assemblages.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
What is the overall chronology of Neolithic activity across the Outer Hebrides?
We still need better resolution on the chronology of all examples of Neolithic activity across the Outer Hebrides. This would be of significant value to furthering Hebridean Neolithic research. A refined chronology would illuminate potential patterns in site types; it would highlight additional gaps in Neolithic research. This question aims to encapsulate domestic, monumental, and any other site type, and it researchers are encouraged to make use of grey, published, and unpublished data for initial data collation. Further, systematic dating of collections in museums and Comann Eachdraidh is recommended. Researchers are encouraged to make use of grey, published, and unpublished data for initial data collation. Further, systematic dating of collections in museums and Comann Eachdraidh is recommended.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
What was the chronology of the Mesolithic-Neolithic transition across the Outer Hebrides?
Transitionary periods are notoriously tricky to pin down. The Hebridean Mesolithic-Neolithic transition is especially so, given how few known Mesolithic sites have been identified across these islands. When did this transition begin? What were the mechanisms and processes? How do they compare with other areas such as Orkney, Shetland and the Scottish mainland? Additionally, what did this transitionary period look like? Reassessment and reanalysis of existing datasets, reports, archives and collections, alongside new programmes of meaningful scientific dating, are likely ways forward. In a developer-funded context, the research significance of dating and other post-excavation work needs to be emphasised.
Status:
Active
Date accepted:
26/08/2026
Date of next review:
26/08/2031
When did the Outer Hebrides convert to Christianity?
It is still not known when conversion to Christianity took place in the Outer Hebrides nor how this happened. The Papar Project has indicated placename evidence for holy sites among the Outer Hebridean islands. Were these the first of their kind or were they constructed on top of previous ‘holy’ (albeit pagan) sites? What is the overall chronology for the emergence and expansion of early Christian sites across the Outer Hebrides? When does Christian iconography and material start to appear in other settings? At what point did Christian sites dominate and begin to define the structure of the Hebridean landscape?
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