Alex Bayliss

Rolling Out Revolution: Using Radiocarbon Dating in Archaeology

Sixty years ago, the advent of radiocarbon dating rewrote archaeological chronologies around the world. Forty years ago, the advent of calibration signaled the death knell of the diffusionism that had been the mainstay of archaeological thought for a century. Since then, the revolution has continued, as the extent of calibration has been extended ever further back and as the range of material that can be dated has been expanded. Now a new revolution beckons, one that could allow archaeology to engage in historical debate and usher in an entirely new kind of (pre)history. This paper focuses on more than a decade of experience in utilizing Bayesian approaches routinely for the interpretation of 14 C dates in English archaeology, discussing both the practicalities of implementing these methods and their potential for changing archaeological thinking.

Quality in Bayesian chronological models in archaeology

Abstract Bayesian chronological modelling is fast becoming the method of choice for the interpretation of radiocarbon dates in archaeological and palaeoenvironmental studies around the world. Although software enabling the routine application of the method has been available for more than twenty years, more than half of published models have appeared in the past five years. Unfortunately, the pace of development in statistical methodology has not been matched by the increased care in sample selection and reporting that is required for robust modelling. Barely half the applications considered in this article provide the information necessary to assess the models presented critically. This article discusses what information is required to allow the quality of Bayesian chronological models to be assessed, and provides check-lists for authors, editors and referees, in the hope of improving current practice.

Fragmenting times: interpreting a Bayesian chronology for the Late Neolithic occupation of Çatalhöyük East, Turkey

Abstract 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.

The world recreated: redating Silbury Hill in its monumental landscape

A classic exposition of the difficulties of dating a major monument and why it matters. Silbury Hill, one of the worlds largest prehistoric earth mounds, is too valuable to take apart, so we are reliant on samples taken from tunnels and chance exposures. Presenting a new edition of thirty radiocarbon dates, the authors offer models of short- or long-term construction, and their implications for the ritual landscape of Silbury and Stonehenge. The sequence in which monuments, and bits of monuments, were built gives us the kind and history of societies doing the building. So nothing matters more than the dates…

VALIDATING AND IMPROVING ARCHAEOLOGICAL PHASING AT ST. MARY SPITAL, LONDON

This paper outlines the radiocarbon program applied to the excavation and skeletal assemblage from the cem- etery of the medieval Priory and Hospital of St. Mary Spital in London. Problems encountered in dating medieval cemeteries are outlined. The problems were addressed through the application of Bayesian modeling to validate and refine conventional approaches to constructing phases of archaeological activity. It should be noted that this project was solely funded by the developer of the land; such projects rarely undertake even modest programs of 14C dating. We aim to show how the invest- ment of a proportionally small sum, compared to the overall project costs, may reap significant benefits.

Ironworking in the bronze age? Evidence from a 10th century BC settlement at hartshill copse, upper bucklebury, West Berkshire

Excavations at Hartshill Copse in 2003 uncovered evidence for Late Bronze Age settlement, securely dated to the 10th century BC, associated with long alignments of closely set posts: prehistoric landscape features with few known parallels. Extensive sampling of the settlement remains yielded quantities of burnt flint and plain Post Deverel-Rimbury potsherds, and, quite unexpectedly, a substantial quantity of iron hammerscale. This paper presents the excavation data, with supporting dating evidence, and the results of detailed analysis of the metallurgical residues. It explores the spatial distribution of artefact types within the settlement, and presents an interpretative model for settlement use. The nature of the settlement, with its carefully planned use of space and close relationship with the post alignments, is then discussed. Together, all this provides conclusive evidence for the earliest ironworking site yet recognised in Britain. The paper concludes with a comprehensive discussion of early ironworking in its British and European context.

Recent Research at Duggleby Howe, North Yorkshire

Excavated by John Mortimer at the end of the nineteenth century, Duggleby Howe, near the source of the Gypsey Race in the Yorkshire Wolds, is one of the most iconic round barrow sites of the British Neolithic, not least because of Mortimers detailed description, his schematic section and the range of prestige goods associated with the burials. Despite the re-assessment of Mortimers archive by other authorities over the last twenty years, no absolute dates existed for this important burial sequence. This project re-examines not just the burial evidence, but also the associated earthworks of the barrow including the first geophysical and topographical survey of the surrounding causewayed enclosure. The report also provides a radiocarbon-dated chronology for the burial sequence and mound construction, as well as an assessment of the surviving human and faunal remains.

Informing Conservation: towards 14C wiggle-matching of short tree-ring sequences from medieval buildings in England

This study tested whether accurate dating by accelerator mass spectrometry (AMS) radiocarbon wiggle-matching of short tree-ring series (~30 annual rings) in the Medieval period could be achieved. Scientific dating plays a central role in the conservation of historic buildings in England. Precise dating helps assess the significance of particular buildings or elements of their fabric, thus allowing us to make informed decisions about their repair and protection. Consequently, considerable weight, both financial and legal, can be attached to the precision and accuracy of this dating. Dendrochronology is the method of choice, but in a proportion of cases this is unable to provide calendar dates. Hence, we would like to be able to use 14 C wiggle-matching to provide a comparable level of precision and reliability, particularly on shorter tree-ring sequences (~30 annual growth rings) that up until now would not routinely be sampled. We present the results of AMS wiggle-matching five oak tree-ring sequences, spanning the period covered by the vast majority of surviving Medieval buildings in England (about AD 1180–1540) when currently we have only decadal and bidecadal calibration data.

A Puzzling Body from the River Thames in London

Radiocarbon measurements on a partially articulated female human skeleton, recovered from the foreshore of the river Thames in London, raised interesting questions of interpretation when the body did not produce the anticipated Neolithic date. A relatively recent 14C age and a strong marine component to the individuals diet, identified by stable isotope measurements, means that the date of death is difficult to estimate accurately, although the body probably does not constitute a forensic case.

The Cultural Project: Formal Chronological Modelling of the Early and Middle Neolithic Sequence in Lower Alsace

Starting from questions about the nature of cultural diversity, this paper examines the pace and tempo of change and the relative importance of continuity and discontinuity. To unravel the cultural project of the past, we apply chronological modelling of radiocarbon dates within a Bayesian statistical framework, to interrogate the Neolithic cultural sequence in Lower Alsace, in the upper Rhine valley, in broad terms from the later sixth to the end of the fifth millennium cal BC. Detailed formal estimates are provided for the long succession of cultural groups, from the early Neolithic Linear Pottery culture (LBK) to the Bischheim Occidental du Rhin Supérieur (BORS) groups at the end of the Middle Neolithic, using seriation and typology of pottery as the starting point in modelling. The rate of ceramic change, as well as frequent shifts in the nature, location and density of settlements, are documented in detail, down to lifetime and generational timescales. This reveals a Neolithic world in Lower Alsace busy with comings and goings, tinkerings and adjustments, and relocations and realignments. A significant hiatus is identified between the end of the LBK and the start of the Hinkelstein group, in the early part of the fifth millennium cal BC. On the basis of modelling of existing dates for other parts of the Rhineland, this appears to be a wider phenomenon, and possible explanations are discussed; full reoccupation of the landscape is only seen in the Grossgartach phase. Radical shifts are also proposed at the end of the Middle Neolithic.