The IntCal family of radiocarbon (14C) calibration curves is based on research spanning more than three decades. The IntCal group have collated the 14C and calendar age data (mostly derived from primary publications with other types of data and meta-data) and, since 2010, made them available for other sorts of analysis through an open-access database. This has ensured transparency in terms of the data used in the construction of the ratified calibration curves. As the IntCal database expands, work is underway to facilitate best practice for new data submissions, make more of the associated metadata available in a structured form, and help those wishing to process the data with programming languages such as R, Python, and MATLAB. The data and metadata are complex because of the range of different types of archives. A restructured interface, based on the “IntChron” open-access data model, includes tools which allow the data to be plotted and compared without the need for export. The intention is to include complementary information which can be used alongside the main 14C series to provide new insights into the global carbon cycle, as well as facilitating access to the data for other research applications. Overall, this work aims to streamline the generation of new calibration curves.

Land divisions are ubiquitous features of the British countryside. Field boundaries, enclosures, pit alignments, and other forms of land division have been used to shape and delineate the landscape over thousands of years. While these divisions are critical for understanding economies and subsistence, the organization of tenure and property, social structure and identity, and their histories of use have remained unclear. Here, the authors present the first robust, Bayesian statistical chronology for land division over three millennia within a study region in England. Their innovative approach to investigating long-term change demonstrates the unexpected scale of later ‘prehistoric’ land demarcation, which may correspond to the beginnings of increasing social hierarchy.

The Copper Age cemetery in Varna, Bulgaria, is famous for the earliest known, massive deposition of exquisite golden artefacts. Radiocarbon dating of the Varna i cemetery, excavated in the period 1972–91, places it in the mid-fifth millennium bc and suggests a duration of c 225 years from c 4550 to c 4325 cal bc. Construction work in the adjacent area (2.5 km to the east of Varna i cemetery) in December 2017 led to the discovery of sixteen new graves, whose characteristics are identical to the burials in the cemetery investigated in the last century. This article discusses the AMS dates of ten newly discovered inhumations. The results match well the existing cemetery chronology, showing that the new graves start slightly later and end earlier than Varna i and have a shorter duration of probably no more than a few decades. It is demonstrated for the first time that some areas of burial on the terrace were in continuous use for one or two generations only, suggesting multi-focal depositional activities as opposed to expedient and opportunistic spatial utilisation.

Radiocarbon (14C) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric 14C concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international 14C calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable 14C offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the 14C ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine 14C data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

We undertook a strengths, weaknesses, opportunities, and threats (SWOT) analysis of Northern Hemisphere tree-ring datasets included in IntCal20 in order to evaluate their strategic fit with the demands of archaeological users. Case studies on wiggle-matching single tree rings from timbers in historic buildings and Bayesian modeling of series of results on archaeological samples from Neolithic long barrows in central-southern England exemplify the archaeological implications that arise when using IntCal20. The SWOT analysis provides an opportunity to think strategically about future radiocarbon (14C) calibration so as to maximize the utility of 14C dating in archaeology and safeguard its reputation in the discipline.

Early researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older.

In 2018 Pearson et al. published a new sequence of annual radiocarbon (14C) data derived from oak (Quercus sp.) trees from Northern Ireland and bristlecone pine (Pinus longaeva) from North America across the period 1700–1500 BC. The study indicated that the more highly resolved shape of an annually based calibration dataset could improve the accuracy of 14C calibration during this period. This finding had implications for the controversial dating of the eruption of Thera in the Eastern Mediterranean. To test for interlaboratory variation and improve the robustness of the annual dataset for calibration purposes, we have generated a replicate sequence from the same Irish oaks at ETH Zürich. These data are compatible with the Irish oak 14C dataset previously produced at the University of Arizona and are used (along with additional data) to examine inter-tree and interlaboratory variation in multiyear annual 14C time-series. The results raise questions about regional 14C offsets at different scales and demonstrate the potential of annually resolved 14C for refining subdecadal and larger scale features for calibration, solar reconstruction, and multiproxy synchronization.

Since 1993 Historic England (and its predecessor English Heritage) has commissioned 9074 radiocarbon (14C) measurements on archaeological samples. Over 80% of these have been interpreted within formal Bayesian statistical models. The multiple strands of reinforcing evidence incorporated in these models provide precise chronologies that make stringent demands on the accuracy of the 14C results included in the analysis. Inter-laboratory replication is consequently a routine part of model construction and validation. We report an analysis of replicate measurements on 1089 archaeological samples. It is clear that laboratory reproducibility accounts for only part of the observed variation. The type of material dated is also critical to the reproducibility of measurements, with some sample types proving particularly problematic.

New radiocarbon dating and chronological modelling have refined understanding of the character and circumstances of flint mining at Grime’s Graves through time. The deepest, most complex galleried shafts were worked probably from the third quarter of the 27th century cal bc and are amongst the earliest on the site. Their use ended in the decades around 2400 cal bc, although the use of simple, shallow pits in the west of the site continued for perhaps another three centuries. The final use of galleried shafts coincides with the first evidence of Beaker pottery and copper metallurgy in Britain. After a gap of around half a millennium, flint mining at Grime’s Graves briefly resumed, probably from the middle of the 16th century cal bc to the middle of the 15th. These ‘primitive’ pits, as they were termed in the inter-war period, were worked using bone tools that can be paralleled in Early Bronze Age copper mines. Finally, the scale and intensity of Middle Bronze Age middening on the site is revealed, as it occurred over a period of probably no more than a few decades in the 14th century cal bc. The possibility of connections between metalworking at Grime’s Graves at this time and contemporary deposition of bronzes in the nearby Fens is discussed.

Longhouses are a key feature of Neolithic Linearbandkeramik (LBK) settlements in Central Europe, but debate persists concerning their usage, longevity and social significance. Excavations at Versend-Gilencsa in south-west Hungary (c. 5200 cal BC) revealed clear rows of longhouses. New radiocarbon dates suggest that these houses experienced short lifespans. This paper produces a model for the chronology of Versend, and it considers the implications of the new date estimates for a fuller understanding of the layout and duration of LBK longhouse settlements.

Since its publication in 1954 Star Carr has held an iconic status in British Mesolithic archaeology. The original excavations at the site recorded a large assemblage of bone and antler tools from a sequence of peat deposits at the edge of the Lake Flixton. Over 60 years later this remains the largest assemblage of bone and antler artefacts of its date in Britain and has been an invaluable source of information for life in the early Mesolithic. However, the interpretation of this material has been the subject of intense debate, and the assemblage has been variously described as the remains of an in situ settlement, a refuse dump, and the result of culturally prescribed acts of deposition. Fundamentally, these very different ideas of the nature of the site depend on differing interpretations of the environmental context into which the majority of the organic artefacts were deposited. This paper presents the results of recent work at Star Carr that helps to resolve the debate surrounding both the context of the assemblage and the motivations that lay behind its deposition.

Archaeological fieldwork preceding housing development revealed a Mesolithic site in a primary context. A central hearth was evident from a cluster of calcined flint and bone, the latter producing a modelled date for the start of occupation at 8220–7840 cal bc and ending at 7960–7530 cal bc (95% probability). The principal activity was the knapping of bladelets, the blanks for microlith production. Impact-damaged microliths indicated the re-tooling of hunting weaponry, while microwear analysis of other tools demonstrated hide working and butchery activity at the site. The lithics can be classified as a Honey Hill assemblage type on the basis of distinctive leaf-shaped microlithic points with inverse basal retouch.

Such assemblages have a known concentration in central England and are thought to be temporally intermediate between the conventional British Early and Late Mesolithic periods. The lithic assemblage is compared to other Honey Hill type and related Horsham type assemblages from south-eastern England. Both assemblage types are termed Middle Mesolithic and may be seen as part of wider developments in the late Preboreal and Boreal periods of north-west Europe. Rapid climatic warming at this time saw the northward expansion of deciduous woodland into north-west Europe. Emerging new ecosystems presented changes in resource patterns and the Middle Mesolithic lithic typo-technological developments reflect novel foraging strategies as adaptations to the new opportunities of Boreal forest conditions. While Honey Hill-type assemblages are seen as part of such wider processes their distinctive typological signature attests to autochthonous, regional developments of human groups infilling the landscape. Such cultural insularity may reflect changing social boundaries with reduction in mobility range and physical isolation caused by rising sea level and the creation of the British archipelago.

Orkney is internationally recognised for its exceptionally well-preserved Neolithic archaeology. The chronology of the Orcadian Neolithic is, however, relatively poorly defined. The authors analysed a large body of radiocarbon and luminescence dates, formally modelled in a Bayesian framework, to address the timescape of Orkney's Late Neolithic. The resultant chronology for the period suggests differences in the trajectory of social change between the ‘core’ (defined broadly as the World Heritage site) and the ‘periphery’ beyond. Activity in the core appears to have declined markedly from c. 2800 cal BC, which, the authors suggest, resulted from unsustainable local political tensions and social concerns.

There is a considerable mix of models for house durations in the literature on Neolithic Europe. This article presents a summary of a formal chronological model for the Neolithic tell of Uivar in western Romania. We provide estimates of house duration and relate houses to other features of the development of this tell, from the later sixth to the mid-fifth millennium cal bc. Three wider implications are discussed: that the house must be contextualized case by case; that house duration gives powerful insights into the sociality of community; and that houses, surprisingly often taken rather for granted in Neolithic archaeology, should be fully integrated into the interpretation of Neolithic histories. From what perspective, anthropocentric or relational, that may best be done, is open to question; while it may be helpful to think in this case in terms of the lives and vitality of houses, the ability of people to create and vary history should not be set aside lightly.

In the context of unanswered questions about the nature and development of the Late Neolithic in Orkney, we present a summary of research up to 2015 on the major site at the Ness of Brodgar, Mainland Orkney, concentrating on the impressive buildings. Finding sufficient samples for radiocarbon dating was a considerable challenge. There are indications, from both features and finds, of activity pre-dating the main set of buildings exposed so far by excavation. Forty-six dates on thirty-nine samples are presented and are interpreted in a formal chronological framework. Two models are presented, reflecting different possible readings of the sequence. Both indicate that piered architecture was in use by the thirtieth century cal bc and that the massive Structure 10, not the first building in the sequence, was also in existence by the thirtieth century cal bc. Activity associated with piered architecture came to an end (in Model 2) around 2800 cal bc. Midden and rubble infill followed. After an appreciable interval, the hearth at the centre of Structure 10 was last used around 2500 cal bc, perhaps the only activity in an otherwise abandoned site. The remains of some 400 or more cattle were deposited over the ruins of Structure 10: in Model 2, in the mid-twenty-fifth century cal bc, but in Model 1 in the late twenty-fourth or twenty-third century cal bc. The chronologies invite comparison with the near-neighbour of Barnhouse, in use from the later thirty-second to the earlier twenty-ninth century cal bc, and the Stones of Stenness, probably erected by the thirtieth century cal bc. The Ness, including Structure 10, appears to have outlasted Barnhouse, but probably did not endure as long in its primary form as previously envisaged. The decay and decommissioning of the Ness may have coincided with the further development of the sacred landscape around it; but precise chronologies for other sites in the surrounding landscape are urgently required. The spectacular feasting remains of several hundred cattle deposited above Structure 10 may belong to a radically changing world, coinciding (in Model 2) with the appearance of Beakers nationally, but it was arguably the, by now, mythic status of that building which drew people back to it.

A formally modeled radiocarbon chronology for a new profile through the great Neolithic tell of Vinča-Belo Brdo, Serbia, is the third interwoven strand in refining the chronology of the tell. This now joins models for the whole sequence based on the archive of early excavations, and for the last two known horizons at the top of the settlement mound, investigated in recent decades. In the new deep sounding, Vinča culture occupation from the 52nd century cal BC is slightly later than in the main sequence, probably reflecting the horizontal extension of the tell as it began to grow. The last dated occupation falls in the late 47th–early 46th century cal BC, slightly earlier than in the main sequence, but the top of the profile is affected by the slippage that caused the new excavations. Formal estimates are given for the succession and varying durations of burnt and unburnt houses, and indicate a period in the first part of the 5th millennium without house burning. Overall, the combined results from the three interwoven strands serve to produce a radically enhanced understanding of the temporality of the tell, which builds on, rather than supplants, previous research. We knew previously that Vinča-Belo Brdo was very long-lived, but now we can time that history with much greater precision. We can assert with much greater confidence that its vertical buildup was steady and largely uninterrupted. We have begun, from the work on the top of the tell and in the new deep sounding, to grasp better the fluctuations in house durations from generation to generation, and can now contrast the relative fortunes of unburnt and burnt houses. We can say much more about the timing and tempo of the ending of the tell, and about the possible circumstances in which that took place.

Radiocarbon dating and Bayesian chronological modelling, undertaken as part of the investigation by the Times of Their Lives project into the development of Late Neolithic settlement and pottery in Orkney, has provided precise new dating for the Grooved Ware settlement of Barnhouse, excavated in 1985–91. Previous understandings of the site and its pottery are presented. A Bayesian model based on 70 measurements on 62 samples (of which 50 samples are thought to date accurately the deposits from which they were recovered) suggests that the settlement probably began in the later 32nd century cal bc (with Houses 2, 9, 3 and perhaps 5a), possibly as a planned foundation. Structure 8 – a large, monumental structure that differs in character from the houses – was probably built just after the turn of the millennium. Varied house durations and replacements are estimated. House 2 went out of use before the end of the settlement, and Structure 8 was probably the last element to be abandoned, probably during the earlier 29th century cal bc. The Grooved Ware pottery from the site is characterised by small, medium-sized, and large vessels with incised and impressed decoration, including a distinctive, false-relief, wavy-line cordon motif. A considerable degree of consistency is apparent in many aspects of ceramic design and manufacture over the use-life of the settlement, the principal change being the appearance, from c. 3025–2975 cal bc, of large coarse ware vessels with uneven surfaces and thick applied cordons, and of the use of applied dimpled circular pellets. The circumstances of new foundation of settlement in the western part of Mainland are discussed, as well as the maintenance and character of the site. The pottery from the site is among the earliest Grooved Ware so far dated. Its wider connections are noted, as well as the significant implications for our understanding of the timing and circumstances of the emergence of Grooved Ware, and the role of material culture in social strategies.

Bayesian statistical frameworks have been used to calculate explicit, quantified estimates for site chronologies, and have been especially useful for resolving the complex probability distributions of calibrated radiocarbon dates to the level of individual prehistoric lifetimes and generations. Here the technique is applied to the Neolithic tell of Vinča-Belo Brdo in order to answer long-standing questions about the timing and circumstances of its demise. Modelled date estimates place the end of the site in the second half of the forty-sixth century cal BC. Two successive horizons of closely spaced houses each suffered extensive burning; the interval between them was placed at a maximum of 25 years, with the last house probably used for less than 15 years. The evidence suggests that these house burnings were deliberate, and opens new considerations for the causes of the end of the tell-based system in south-east Europe.

New radiocarbon dates for the Neolithic settlement at Pool on Sanday, Orkney, are interpreted in a formal chronological framework. Phases 2.2 and 2.3, during which flat-based Grooved Ware pottery with incised decoration developed, have been modelled as probably dating to between the 31st and 28th centuries cal bc. There followed a hiatus of a century or so, before the resumption of occupation in Phase 3, which has a different Grooved Ware style featuring the use of applied decoration. This has been modelled as probably dating from the 26th to the 24th centuries cal bc. The implications of these results are discussed for the emergence and development of Grooved Ware, and for the trajectory of settlement and monumentality on Sanday.

The repetitive and highly structured domestic architecture of Çatalhöyük is a distinctive feature of this important Neolithic settlement. At the very end of the sequence, however, excavations on the surface of the East Mound reveal changes in household construction and burial chambers. Bayesian analysis of 56 AMS radiocarbon dates from these layers allow the date and pace of these changes to be established in detail. Settlement activity on the East Mound ceased just after 6000 cal BC, and was followed by the cessation of Neolithic burial activity a few decades later.