No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
The Late Glacial human reoccupation of north-western Europe: new approaches to space-time modelling
Abstract
How and when was northern Europe reoccupied at the end of the last Ice Age? Radiocarbon dates from the earliest post-glacial contexts provide one answer: they offer a sequence in which the regions of Europe, from the Upper Rhine to Britain, saw the return of humans. The authors use Bayesian methods to model a chronology and thus arrive at a sequence with clear assessments of uncertainty.
... Some researchers have concluded that this was probably the case (e.g. Blockley et al., 2000a,b;Terberger and Street, 2002;Blackwell and Buck, 2003), while others have argued instead for the greater importance of social and cultural influences, which need not have been driven by climate (e.g. Housley et al., 1997). ...
... The earliest uncalibrated date in each regional dataset was effectively selected to denote the age of the onset of human expansion in each respective region (see Blockley et al., 2000a). This approach has been questioned because (i) uncalibrated dates cannot be compared directly, for the reasons given above, and (ii) the selection of one end member of a dataset as being representative of that dataset can be criticised on statistical grounds (Blockley et al., 2000a;Blackwell and Buck, 2003). ...
... When this approach is adopted, a significantly younger age than those obtained by Housley et al. (1997) for the expansion of humans in each region is suggested (Blockley et al., 2000a,b). This approach has been criticised in turn, however, for there are too few dates to justify the application of Central Limit Theorem in the analysis of some of the regional datasets, owing to the non-normality of the individual date distributions, while the overall spread of the radiocarbon data also renders these combination procedures inappropriate (Blackwell and Buck, 2003). ...
This paper addresses the possible connections between the onset of human
expansion in Europe following the Last Glacial Maximum, and the timing
of abrupt climate warming at the onset of the Lateglacial
(Bölling/Allerød) Interstadial. There are opposing views as
to whether or not human populations and activities were directly forced
by climate change, based on different comparisons between archaeological
and environmental data. We review the geochronological assumptions and
approaches on which data comparisons have been attempted in the past,
and argue that the uncertainties presently associated with age models
based on calibrated radiocarbon dates preclude robust testing of the
competing models, particularly when comparing the data to
non-radiocarbon-based timescales such as the Greenland ice core records.
The paper concludes with some suggestions as to the steps that will be
necessary if more robust tests of the models are to be developed in the
future. Copyright
... This is compounded by the need to use appropriate methods for dealing with the often large uncertainty ranges and non-normal, multi-modal probability densities of calibrated radiocarbon ages. Fortunately there has been significant debate on this topic and a number of Bayesian and classical methods have been proposed for studying radiocarbon data and using them to look at presence or absence of archaeological sites (e.g., Housley et al., 1997;Blockley et al., 2000Blockley et al., , 2006Blackwell and Buck, 2003). One method takes all the available calibrated radiocarbon probability densities for a particular period and these are summed and used to identify peaks and troughs in density. ...
... Moreover there is also the issue that effectively using the numbers of radiocarbon dates to infer relative population size means that the analyses are more prone to issues of sampling or preservation bias inherent in archaeological studies. Many of the problems with this approach are discussed elsewhere (Blackwell and Buck, 2003;Blockley et al., 2006). ...
... Both phases and boundaries have been used extensively in Bayesian studies to calculate the onset and end of various groupings, from archaeologically defined cultures (Blackwell and Buck, 2003;Blockley, 2006), through to depositional events such as tephra (Blockley et al., 2008a,b). The major advantage with this approach is that is far more robust than just using the first and last date to define the start and end of a group, as this means individual dates are cleaved from a group and the inherent uncertainties in any one date would be maximised (Blackwell and Buck, 2003;Blockley, 2006). ...
Quaternary Science Reviews, 30 (2011) 98-108. doi:10.1016/j.quascirev.2010.09.021
... We are interested in seeing the outcome for the cognitive origins synthesis when instead of global questions we examine the historically-contingent processes of population contraction and expansion in well-researched landscapes during times of marked climatic change. The advantage of radiocarbon is that, for all its problems of calibration and statistical reliability (Blackwell & Buck 2003), it nonetheless provides a chronological framework whose precision can be refined within scientific and operational parameters (e.g.Lowe et al. 2001). In the study of population history, a radiocarbon chronology is therefore to be preferred to either the molecular or speaking clock, based respectively on genetic and linguistic evidence. ...
... We interpret the changing frequencies of calibrated determinations inFigure 1as a proxy for the timing and direction of demic expansion as well as relative levels of human activity between regions. This method, using dates-as-data, is an established technique to investigate a process such as population dispersal into unoccupied habitats (Blackwell & Buck 2003;Holdaway & Porch 1995;Housley et al. 1997;Lourandos & David 2002;Rick 1987;Ross 2001;van Andel et al. 2003). On this basis we recognize five major population events for Late Glacial western Europe (Tables 3 & 4), discussed in detail below. ...
... , Department of Archaeology, University of Glasgow, Glasgow, G12 8QQ, Scotland, UK; r.housley@archaeology.gla.ac.uk. This latest contribution by Gamble and his colleagues is one of a growing number of papers (e.g.Blackwell & Buck 2003;Lourandos & David 2002;Holdaway & Porch 1995;Housley et al. 1997;Rick 1987;Ross 2001) that in the last two decades have used radiocarbon 'dates-as-data' as a proxy for population history or as a means to explore patterns of population dispersal on a regional or sub-continental scale. Significantly, they attempt to distance the study of population history from the twin influences represented by the agriculturalist 'wave of advance' and the spread of the major language groups. ...
This article presents the initial results from the S2AGES data base of calibrated radiocarbon estimates from western Europe in the period 25,000–10,000 years ago. Our aim is to present a population history of this sub-continental region by providing a chronologically-secure framework for the interpretation of data from genetics and archaeology. In particular, we define five population events in this period, using dates-as-data, and examine the implications for the archaeology of Late Glacial colonization. We contrast this detailed regional approach to the larger project which we call the cognitive origins synthesis that includes historical linguistics in the reconstruction of population history. We conclude that only archaeology can currently provide the framework for population history and the evaluation of genetic data. Finally, if progress is to be made in the new interdisciplinary field of population history then both disciplines need to refrain from inappropriate agricultural thinking that fosters distorting models of European prehistory, and they should also pay less, if any, attention to historical linguistics.
With comments from L.G. Straus, J.-P. Bocquet-Appel, P.A. Underhill & R. Housley and followed by a reply from the author.
... The applicability of the uniform prior to sedimentary archives has been discussed elsewhere (Bronk Ramsey, 2000; Steier and Rom, 2000; Blackwell and Buck, 2003) but while it is possible that the uniform prior can underestimate the full range of possible ages of calibrated dates in a sequence, due to the possibility of non-linear sedimentation rates between individual calibrated dates, it has been shown that with a reasonable number of dates and appropriate nesting of sequences within boundaries , that the method can reliably reconstruct sedimentation rates within model uncertainty that are significantly smaller than if the dates were calibrated on their own. ...
... The applicability of the uniform prior to sedimentary archives has been discussed elsewhere (Bronk Ramsey, 2000; Steier and Rom, 2000; Blackwell and Buck, 2003) but while it is possible that the uniform prior can underestimate the full range of possible ages of calibrated dates in a sequence, due to the possibility of non-linear sedimentation rates between individual calibrated dates, it has been shown that with a reasonable number of dates and appropriate nesting of sequences within boundaries , that the method can reliably reconstruct sedimentation rates within model uncertainty that are significantly smaller than if the dates were calibrated on their own. Nevertheless, the use of the uniform prior has never been tested on varying sedimentation rates in an exhaustive a sense as the test described here and given the increased use of the method (e.g. ...
The growing importance of understanding past abrupt climate variability at a regional and global scale has led to the realisation that independent chronologies of past environmental change need to be compared between various archives. This has in turn led to attempts at significant improvements in the required precision at which records can be dated. Radiocarbon dating is still the most prominent method for dating organic material from terrestrial and marine archives, and as such many of the recent developments in improving precision have been aimed at this technique. These include: (1) selection of the most suitable datable fractions within a record, (2) the development of better calibration curves, and (3) more precise age modelling techniques. While much attention has been focussed on the first two items, testing the possibilities of the relatively new age modelling approaches has not received much attention. Here, we test the potential for methods designed to significantly improve precision in radiocarbon-based age models, wiggle match dating and various forms of Bayesian analyses. We demonstrate that while all of the methods can perform very well, in some scenarios, caution must be taken when applying them. It appears that an integrated approach is required in real life dating situations where more than one model is applied, with strict error calculation, and with the integration of radiocarbon data with sedimentological analyses of site formation processes.
... As a result there are two commonly adopted approaches to such problems. The simplest is to spatially partition the data and then analyse the spatial groups within a purely temporal model (as, for example, in Blackwell andBuck, 2003). A more sophisticated approach is to develop a mechanistic (typically deterministic) model for the spatial process (such as demographic spread) and then to use statistical methods to compare the resulting spread patterns with the available chronological evidence using formal statistical methodology (as, for example, inBaggaley et al., 2012a,b). ...
Due to freely available, tailored software, Bayesian statistics is fast becoming the dominant paradigm in archaeological chronology construction. Such software provides users with powerful tools for Bayesian inference for chronological models with little need to undertake formal study of statistical modelling or computer programming. This runs the risk that it is reduced to the status of a black-box which is not sensible given the power and complexity of the modelling tools it implements. In this paper we seek to offer intuitive insight to ensure that readers from the archaeological research community who use Bayesian chronological modelling software will be better able to make well educated choices about the tools and techniques they adopt. Our hope is that they will then be both better informed about their own research designs and better prepared to offer constructively critical assessments of the modelling undertaken by others.
... The last few years saw an exponential increase of archaeological studies that go beyond the simple notion of 14 C as a dating tool, and seek instead to measure less tangible events, such as the rise and fall of cultural phases [25], the timing of colonisation events [34], or the spread of farming [35]. The use of SPD of 14 C dates as proxy of ancient demography, for instance, has seen a wide range of applications in Europe and North America, offering new insights and details on the population dynamics of prehistoric societies. ...
Recent advances in the use of summed probability distribution (SPD) of calibrated $^{14}$C dates have opened new possibilities for studying prehistoric demography. The degree of correlation between climate change and population dynamics can now be accurately quantified, and divergences in the demographic history of distinct geographic areas can be statistically assessed. Here we contribute to this research agenda by reconstructing the prehistoric population change of Jomon hunter-gatherers between 7,000 and 3,000 cal BP. We collected 1,433 $^{14}$C dates from three different regions in Eastern Japan (Kanto, Aomori and Hokkaido) and established that the observed fluctuations in the SPDs were statistically significant. We also introduced a new non-parametric permutation test for comparing multiple sets of SPDs that highlights point of divergences in the population history of different geographic regions. Our analyses indicate a general rise-and-fall pattern shared by the three regions but also some key regional differences during the 6$^{th}$ millennium cal BP. The results confirm some of the patterns suggested by previous archaeological studies based on house and site counts but offer statistical significance and an absolute chronological framework that will enable future studies aiming to establish potential correlation with climatic changes.
... So far we have looked at generic, general-purpose models that are applicable to a wide variety of sites and environmental deposits. The Bayesian formalism also allows much more specific models to be generated, which can be used in particular situations such as models that allow for spacial modeling (such as Blackwell and Buck 2003). This is likely to be an area of active development for some time to come and really goes beyond the scope of this paper (a useful general reference is Buck and Millard 2004). ...
If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical methods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14 C calibration curve. In most dating applications, however, we have larger numbers of 14 C measurements and we wish to relate those to events in the past. Bayesian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14 C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal software (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used “uniform phase” models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run simulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing possible problems with statistical models of this kind.
... In conjunction with systematic 14 C dating, Bayesian statistics has exhibited great potential in refining archaeological chronology (Blackwell and Buck 2003; Fuller et al. 2007; Beramendi-Orosco et al. 2009; Higham and Higham 2009). However, the advantage of this method has not been widely appreciated in the archaeological communities yet, and there are only very a few studies that have made use of this method in China (e.g. ...
Technological and theoretical advancements in modern radiocarbon chronology make the precise dating of archaeological and geological events possible. Here, we show examples of how these state-of-the-art methods can be used to establish and refine the archaeological cultural chronology for the Shangluo area in the Qinling Mountains of central China. In this study, the Donglongshan and Zijing sites were dated using the high-precision accelerator mass spectrometry (AMS) 14 C method. Also, detailed magnetic-susceptibility measurements were conducted at both sites to gain preliminary information about past climate changes. The 14 C dates, after being treated with Bayesian statistics, provide a firm constraint on the archaeological chronological framework for this area. Within this framework, the Malan loess-Holocene soil transition can be placed at 10,400–10,090 BC, while the duration of the Yangshao and Longshan cultures was dated to ∼4200–2900 and ∼2900–2100 BC, respectively, revealing an undisrupted history of human occupation in this area until the early dynastic period. Magnetic susceptibility values began to increase in the early Holocene, indicating a progressive amelioration of regional climate. The widespread development of paleosol during the middle Holocene indicates that warm and wet climate conditions prevailed, providing a favorable environmental context within which the Yangshao culture thrived. Magnetic susceptibility values then decreased from ∼2100 BC when the Xia Dynasty started, and loess accumulated again, pointing to cooling and drying climate conditions that may have led to a cultural transition from the Neolithic to the dynastic civilization.
... The last few years saw an exponential increase of archaeological studies that go beyond the simple notion of 14 C as a dating tool, and seek instead to measure less tangible events, such as the rise and fall of cultural phases [25], the timing of colonisation events [34], or the spread of farming [35]. The use of SPD of 14 C dates as proxy of ancient demography, for instance, has seen a wide range of applications in Europe and North America, offering new insights and details on the population dynamics of prehistoric societies. ...
Recent advances in the use of summed probability distribution (SPD) of calibrated 14C dates have opened new possibilities for studying prehistoric demography. The degree of correlation between climate change and population dynamics can now be accurately quantified, and divergences in the demographic history of distinct geographic areas can be statistically assessed. Here we contribute to this research agenda by reconstructing the prehistoric population change of Jomon hunter-gatherers between 7,000 and 3,000 cal BP. We collected 1,433 14C dates from three different regions in Eastern Japan (Kanto, Aomori and Hokkaido) and established that the observed fluctuations in the SPDs were statistically significant. We also introduced a new non-parametric permutation test for comparing multiple sets of SPDs that highlights point of divergences in the population history of different geographic regions. Our analyses indicate a general rise-and-fall pattern shared by the three regions but also some key regional differences during the 6th millennium cal BP. The results confirm some of the patterns suggested by previous archaeological studies based on house and site counts but offer statistical significance and an absolute chronological framework that will enable future studies aiming to establish potential correlation with climatic changes.
... In conjunction with systematic 14 C dating, Bayesian statistics has exhibited great potential in refining archaeological chronology (Blackwell and Buck 2003; Fuller et al. 2007; Beramendi-Orosco et al. 2009; Higham and Higham 2009). However, the advantage of this method has not been widely appreciated in the archaeological communities yet, and there are only very a few studies that have made use of this method in China (e.g. ...
Technological and theoretical advancements in modern radiocarbon chronology make the precise dating of archaeological and geological events possible. Here, we show examples of how these state-of-the-art methods can be used to establish and refine the archaeological cultural chronology for the Shangluo area in the Qinling Mountains of central China. In this study, the Donglongshan and Zijing sites were dated using the high-precision accelerator mass spectrometry (AMS) 14C method. Also, detailed magnetic-susceptibility measurements were conducted at both sites to gain preliminary information about past climate changes. The 14C dates, after being treated with Bayesian statistics, provide a firm constraint on the archaeological chronological framework for this area. Within this framework, the Malan loess-Holocene soil transition can be placed at 10,400-10,090 BC, while the duration of the Yangshao and Longshan cultures was dated to ~4200-2900 and ~2900-2100 BC, respectively, revealing an undisrupted history of human occupation in this area until the early dynastic period. Magnetic susceptibility values began to increase in the early Holocene, indicating a progressive amelioration of regional climate. The widespread development of paleosol during the middle Holocene indicates that warm and wet climate conditions prevailed, providing a favorable environmental context within which the Yangshao culture thrived. Magnetic susceptibility values then decreased from ~2100 BC when the Xia Dynasty started, and loess accumulated again, pointing to cooling and drying climate conditions that may have led to a cultural transition from the Neolithic to the dynastic civilization. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.
... Studies of biological and isotopic proxies in north European natural sedimentary archives (lakes and peat bogs) spanning Termination 1 (c. 15e9 ka) have focused recently on highly age-resolved records, where chronology comes from high precision AMS 14 C dating of chemically characterised fractions (Blockley et al., 2004Blockley et al., , 2007), Bayesian age modelling of contextual relationships (Blackwell and Buck, 2003; Blockley et al., 2008a), the identification of age-constrained tephra isochrones (Blockley et al., 2008b ), and the analysis of laminated (sometimes varved) sediments (MacLeod et al., 2011; Neugebauer et al., 2012; Wulf et al., 2013). Thus Late Glacial environmental archives in northern Europe generally have better age control than corresponding * Corresponding author. ...
The discovery of a cryptotephra (nonvisible volcanic horizon) in a windblown sand archaeological site in Poland highlights how luminescence and tephrostratigraphy may combine to better refine the chronology of such sites. In this study we identify a cryptotephra horizon which on the basis of major and minor element geochemistry and an OSL age of 2.3 ±0.1 ka is correlated to the Glen Garry tephra. The different methodological strengths of OSL and tephrostratigraphy may be harnessed to counter the limitations of a single approach to produce a more secure chronology. Although in this study the tephra deposition event is shown to post-date the archaeological activity, the methodological approach is clearly demonstrated. Further investigations will reveal if cryptotephra layers are commonly preserved in such environmental settings. If this is so then future applications of this approach may prove to be more widely applicable.
... In conjunction with systematic 14 C dating, Bayesian statistics has exhibited great potential in refining archaeological chronology (Blackwell and Buck 2003; Fuller et al. 2007; Beramendi-Orosco et al. 2009; Higham and Higham 2009). However, the advantage of this method has not been widely appreciated in the archaeological communities yet, and there are only very a few studies that have made use of this method in China (e.g. ...
... Although, since the advent of AMS, 14 C dating has been fundamental to our understanding of the period, material suitable for 14 C dating is often scarce, sites may lie beyond the limit of the technique, or other scientific dating methods may be more appropriate. In the Paleolithic, synthetic studies modeling particular archaeological issues (Blackwell and Buck 2003; Blockley et al. 2004) are more common than site-specific applications. ...
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 14C dates in English archaeology, discussing both the practicalities of implementing these methods and their potential for changing archaeological thinking. © 2009 by the Arizona Board of Regents on behalf of the University of Arizona.
... An early example of this byGeyh (1980)used radiocarbon dating evidence from coastal peats to elucidate sea-level curves by plotting probability histograms from the compiled ages, with gaps in the record reflecting retardation of peat development and interpreted as evidence for sea-level rise. Michczyn´skaMichczyn´Michczyn´ska and Pazdur (2004)interpreted the shape of a cumulative probability function (CPF), produced by stacking the probability distributions for individual (>700) calibrated radiocarbon measurements from Polish peat samples, in relation to Holocene climate changes.Blockley et al. (2000)used CPFs to explore the occupation of northwestern Europe by people after deglaciation; however,Blackwell and Buck (2003)criticised their approach on the grounds that the calibrated ages being 'summed' do not relate to the same event, and instead proposed a Bayesian approach to model the dating control for earliest human activity in these regions. Recently the CPF approach has been employed to interrogate regional radiocarbon databases for fluvial environments in Great Britain (Lewin and Macklin, 2003;Lewin et al., 2005;Johnstone et al., 2006;Macklin et al., 2010), Poland (Starkel et al., 2006), Spain (Thorndycraft and Benito, 2006a), India (Kale, 2007), Germany (Hoffmann et al., 2008) and Tunisia (Zielhofer and Faust, 2008). ...
Cumulative probability functions (CPFs) for large numbers of radiocarbon age determinations are increasingly being used by scientists as a methodology to discern environmental histories. While the recent compilation of regional databases of the radiocarbon dating control for fluvial sediment sequences has been beneficial for identifying gaps in knowledge and stimulating new research, there are a number of problems that critically undermine the use of these CPFs as sensitive hydroclimatic proxies. (i) The CPF method is underpinned by the assumption that each radiocarbon measurement is a true age estimate for a point in time, whereas each measured age in fact forms a scatter around the true age of the sample; (ii) calibration of radiocarbon ages is responsible for much of the structure in CPFs and compounds the problem of scatter and smears the chronological control; (iii) the databases incorporate multiple types of environmental changes differing chronological relationships between the 14C measurements and the dated events, with pre-dating, dating or post-dating chronological control each displaying variable length temporal lags all mixed together in the same analysis; and (iv) the radiocarbon ages from individual case studies need to be more robustly tested before being incorporated into regional databases. All these factors negate the value of CPFs as sensitive proxies of environmental change, because peaks in probability for individual radiocarbon measurements are likely to be an incorrect estimate for the age of a geomorphological event and this problem is compounded by combining probabilities for multiple unrelated events. In this paper we present a critical analysis of CPFs and their interpretation before suggesting alternative approaches to analysing radiocarbon geochronologies of geomorphic events, which include: (i) Bayesian age modelling of river terrace development; (ii) developing regional databases that test specific geomorphic hypotheses; (iii) Bayesian age modelling of palaeoflood records; and (iv) analysis of sedimentation rates. Copyright © 2011 John Wiley & Sons, Ltd.
... So far we have looked at generic, general-purpose models that are applicable to a wide variety of sites and environmental deposits. The Bayesian formalism also allows much more specific models to be generated, which can be used in particular situations such as models that allow for spacial modeling (such asBlackwell and Buck 2003). This is likely to be an area of active development for some time to come and really goes beyond the scope of this paper (a useful general reference is Buck and Millard 2004). ...
If radiocarbon measurements are to be used at all for chronological purposes, we have to use statistical meth-ods for calibration. The most widely used method of calibration can be seen as a simple application of Bayesian statistics, which uses both the information from the new measurement and information from the 14 C calibration curve. In most dating applications, however, we have larger numbers of 14 C measurements and we wish to relate those to events in the past. Baye-sian statistics provides a coherent framework in which such analysis can be performed and is becoming a core element in many 14 C dating projects. This article gives an overview of the main model components used in chronological analysis, their mathematical formulation, and examples of how such analyses can be performed using the latest version of the OxCal soft-ware (v4). Many such models can be put together, in a modular fashion, from simple elements, with defined constraints and groupings. In other cases, the commonly used "uniform phase" models might not be appropriate, and ramped, exponential, or normal distributions of events might be more useful. When considering analyses of these kinds, it is useful to be able run sim-ulations on synthetic data. Methods for performing such tests are discussed here along with other methods of diagnosing pos-sible problems with statistical models of this kind.
... These types of models are well established in archaeology (e.g. Blackwell and Buck 2003;Blockley et al., 2006); are being applied directly to questions in Quaternary geology Christen, 2005, Blockley et al., 2004, in press) and are beginning to be applied to the age modelling of the timing of volcanic eruptions (Davies et al., 2004;Wohlfarth et al., 2006). Furthermore, recent testing of the potential of these modelling methods through simulation of radiocarbon dates and depositional scenarios have proven highly successful (Blockley, 2003;Blockley et al., 2007). ...
The role of tephrochronology, as a dating and stratigraphic tool, in precise palaeoclimate and environmental reconstruction, has expanded significantly in recent years. The power of tephrochronology rests on the fact that a tephra layer can stratigraphically link records at the resolution of as little as a few years, and that the most precise age for a particular tephra can be imported into any site where it is found. In order to maximise the potential of tephras for this purpose it is necessary to have the most precise and robustly tested age estimate possible available for key tephras. Given the varying number and quality of dates associated with different tephras it is important to be able to build age models to test competing tephra dates. Recent advances in Bayesian age modelling of dates in sequence have radically extended our ability to build such stratigraphic age models. As an example of the potential here we use Bayesian methods, now widely applied, to examine the dating of some key Late Quaternary tephras from Italy. These are: the Agnano Monte Spina Tephra (AMST), the Neapolitan Yellow Tuff (NYT) and the Agnano Pomici Principali (APP), and all of them have multiple estimates of their true age. Further, we use the Bayesian approaches to generate a revised mixed radiocarbon/varve chronology for the important Lateglacial section of the Lago Grande Monticchio record, as a further illustration of what can be achieved by a Bayesian approach. With all three tephras we were able to produce viable model ages for the tephra, validate the proposed 40Ar/39Ar age ranges for these tephras, and provide relatively high precision age models. The results of the Bayesian integration of dating and stratigraphic information, suggest that the current best 95% confidence calendar age estimates for the AMST are 4690–4300 cal BP, the NYT 14320–13900 cal BP, and the APP 12380–12140 cal BP.
... Questions (1) and (2) are most easily answered when dealing with pairs of sites; we can use the method outlined above. When dealing with multiple sites we can use rankings (as discussed by Blackwell and Buck, 2003;Buck and Bard, 2007), which can also illustrate uncertainty in ordering. ...
The dating of depths in two or more cores is frequently followed by a study of the synchroneity or otherwise of events reflected in the cores. The difficulties most frequently encountered are: (a) determining precisely the depths associated with the events; and (b) determining the ages associated with the depths. There has been much progress in recent years in developing tools for the study of uncertainties in establishing chronologies. This has not yet been matched by similar progress in modelling event/depth relationships. This paper proposes a simple and flexible approach, showing how uncertain events can be married to uncertain chronologies.
Difficulties in studying event/depth/age relationships typically involve a confounding of two different problems. First, what exactly do we mean by an ‘event’ – a point in history, a single depth in the core corresponding to a single time, or a depth/time range? Sometimes ‘event’ is in fact a shorthand for a space-time process. Do the data reflect more than one type of event/process? This can reflect vagueness in definition. Second, what are the sources and implications of the uncertainties?
Here we illustrate the issues involved by examination of several features seen in north European Holocene pollen records. The Alnus rise is regarded as a diachronous early Holocene event; in contrast the Ulmus decline is widely seen as a near synchronous event in the mid-Holocene. The third feature we examine is the interval between the Ulmus decline and the first occurrence of Cerealia-type pollen. The evidence for these events lies in cores of lake sediment from which are determined: (a) the proportions of pollen at many depths; and (b) radiocarbon age estimates from, usually, fewer depths. For this illustration we focus on six sites.
We draw attention to a new and flexible method (implemented in the free R software package Bchron; [Haslett, J., Parnell, A., 2008. A simple monotone process with application to radiocarbon dated depth chronologies. Journal of the Royal Statistical Society: Series C 57 (4), 399–418]) for the establishment of the uncertainties surrounding the dating of samples in such cores. We illustrate its flexibility by assessing the synchroneity of past events.
OPEN-ACCESS, SEE https://rdcu.be/b6e3t FOR FULL LIST OF AUTHORS
Broomcorn millet (Panicum miliaceum L.) is not one of the founder crops domesticated in Southwest Asia in the early Holocene, but was domesticated in northeast China by 6000 BC. In Europe, millet was reported in Early Neolithic contexts formed by 6000 BC, but recent radiocarbon dating of a dozen 'early' grains cast doubt on these claims. Archaeobotanical evidence reveals that millet was common in Europe from the 2nd millennium BC, when major societal and economic transformations took place in the Bronze Age. We conducted an extensive programme of AMS-dating of charred broomcorn millet grains from 75 prehistoric sites in Europe. Our Bayesian model reveals that millet cultivation began in Europe at the earliest during the sixteenth century BC, and spread rapidly during the fifteenth/fourteenth centuries BC. Broomcorn millet succeeds in exceptionally wide range of growing conditions and completes its lifecycle in less than three summer months. Offering an additional harvest and thus surplus food/fodder, it likely was a transformative innovation in European prehistoric agriculture previously based mainly on (winter) cropping of wheat and barley. We provide a new, high-resolution chronological framework for this key agricultural development that likely contributed to far-reaching changes in lifestyle in late 2nd millennium BC Europe.
The inception of the radiocarbon dating method in 1949 was immediately supported by many archaeologists. In the following 2 decades, many important archaeological sites in the Old World were dated, marking the beginning of building a reliable chronological framework for prehistoric and early historic cultural complexes worldwide. The author presents an observation of some of the most important results in establishing a chronology for Old World archaeology, based on 14C dating performed in the last 50 yr. An extensive bibliography should help scholars to get acquainted with early summaries on archaeological chronologies based on 14C data and their evaluation, as well as with some recent examples of the application of 14C dating in Old World archaeology. © 2009 by the Arizona Board of Regents on behalf of the University of Arizona.
Radiocarbon is by far and away the most widely used dating tool in the Late Quaternary. Hundreds of key papers rely on the method to provide absolute and relative chronological information on important topics, including the late evolution of our own species (e.g. Higham et al. 2006a) and the timing and nature of abrupt climatic changes during the last glaciation (Lowe et al. 2001). Calibration of 14 C determinations is an essential part of the dating process, and the implications of calibration can lead to significant differences in the interpretation of important processes (Blockley et al. 2006). Any development that enhances the accuracy, precision, or time coverage of the calibration curves is therefore to be welcomed. Since the early 1980s, there has been periodic publication of carefully vetted data in the form of internationally recognized consensus calibration curves that have allowed 14 C users to convert their raw 14 C determinations into calendar ages (Klein et al. 1982; Stuiver and Reimer 1986, 1993; Stuiver et al. 1998; Reimer et al. 2004). In the beginning, the basis on which this was done was easy to understand, 14 C measurements were made on tree rings and the absolute calendar age came from counting annual growth rings. Although not without its complexities, the terrestrial tree-ring approach remains the most certain method and is at the heart of calibration process in the period 0–12.4 cal kyr. However, for periods beyond the limit of the tree-ring sequences the situation was significantly more problematic, and at times, even controversial.
Few places worldwide experienced Late Glacial ecological shifts as drastic as those seen in the areas covered by, or adjacent to, the massive ice sheets that blanketed much of the northern hemisphere. Among the most heavily glaciated regions, northern Europe underwent substantial ecological shifts during and after the Last Glacial Maximum. The climatically unstable Pleistocene–Holocene transition repeatedly transformed far-northern Europe, placing it among the last regions to be colonized by Paleolithic societies. As such, it shares paleoenvironmental and archaeological analogues with other once glaciated areas where human populations, entrenched in periglacial environments prior to glacier retreat, spread into newly deglaciated territories. Perhaps most significant for northern Europeans were post-glacial effects of the Younger Dryas and Preboreal periods, as shifts in climate, plant, and animal communities elicited several adaptive responses including innovation, exploration, and the eventual settlement of once glaciated landscapes. This paper is a detailed review of existing archaeological and paleoecological evidence pertaining to the Late Upper Paleolithic of northern Europe, and offers theoretical observations on human colonization models and ecological responses to large-scale stadial and interstadial events.
Demographic change has recently re-emerged as a key explanation for socio-cultural changes documented in the prehistoric archaeological record. While the majority of studies of Pleistocene demography have been conducted by geneticists, the archaeological records of the Palaeolithic should not be ignored as a source of data on past population trends. This paper forms both a comprehensive synthesis and the first critical review of current archaeological research into Palaeolithic demography. Within prevailing archaeological frameworks of dual inheritance theory and human behavioural ecology, I review the ways in which demographic change has been used as an explanatory concept within Palaeolithic archaeology. I identify and discuss three main research areas which have benefitted from a demographic approach to socio-cultural change: (1) technological stasis in the Lower Palaeolithic, (2) the Neanderthal-Homo sapiens transition in Europe and (3) the emergence of behavioural modernity. I then address the ways in which palaeodemographic methods have been applied to Palaeolithic datasets, considering both general methodological concerns and the challenges specific to this time period. Finally, I discuss the ability of ethnographic analogy to aid research into Palaeolithic demography.
The Late Pleistocene global extinction of many terrestrial mammal species has been a subject of intensive scientific study for over a century, yet the relative contributions of environmental changes and the global expansion of humans remain unresolved. A defining component of these extinctions is a bias toward large species, with the majority of small-mammal taxa apparently surviving into the present. Here, we investigate the population-level history of a key tundra-specialist small mammal, the collared lemming (Dicrostonyx torquatus), to explore whether events during the Late Pleistocene had a discernible effect beyond the large mammal fauna. Using ancient DNA techniques to sample across three sites in North-West Europe, we observe a dramatic reduction in genetic diversity in this species over the last 50,000 y. We further identify a series of extinction-recolonization events, indicating a previously unrecognized instability in Late Pleistocene small-mammal populations, which we link with climatic fluctuations. Our results reveal climate-associated, repeated regional extinctions in a keystone prey species across the Late Pleistocene, a pattern likely to have had an impact on the wider steppe-tundra community, and one that is concordant with environmental change as a major force in structuring Late Pleistocene biodiversity.
The Late Pleistocene global extinction of many terrestrial mammal
species has been a subject of intensive scientific study for over a
century, yet the relative contributions of environmental changes
and the global expansion of humans remain unresolved. A defining
component of these extinctions is a bias toward large species, with
the majority of small-mammal taxa apparently surviving into the
present. Here, we investigate the population-level history of a key
tundra-specialist small mammal, the collared lemming (Dicrostonyx
torquatus), to explore whether events during the Late Pleistocene
had a discernible effect beyond the large mammal fauna. Using
ancient DNA techniques to sample across three sites in North-West
Europe, we observe a dramatic reduction in genetic diversity in this
species over the last 50,000 y. We further identify a series of extinction-
recolonization events, indicating a previously unrecognized
instability in Late Pleistocene small-mammal populations,
which we link with climatic fluctuations. Our results reveal climateassociated,
repeated regional extinctions in a keystone prey species
across the Late Pleistocene, a pattern likely to have had an impact
on the wider steppe-tundra community, and one that is concordant
with environmental change as a major force in structuring Late
Pleistocene biodiversity.
Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 14C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bølling-Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle.
The Bourewa beach site on the Rove Peninsula of Viti Levu is the earliest known human settlement in the Fiji Islands. How did the settlement at Bourewa develop in space and time? We have radiocarbon dates on sixty specimens, found in association with evidence for human presence, taken from pits across the site. Owing to the lack of diagnostic stratigraphy, there is no direct archaeological evidence for distinct phases of occupation through the period of interest. We give a spatio-temporal analysis of settlement at Bourewa in which the deposition rate for dated specimens plays an important role. Spatio-temporal mapping of radiocarbon date intensity is confounded by uneven post-depositional thinning. We assume that the confounding processes act in such a way that the absence of dates remains informative of zero rate for the original deposition process. We model and fit the onset-field, that is, we estimate for each location across the site the time at which deposition of datable specimens began. The temporal process generating our spatial onset-field is a model of the original settlement dynamics. Comment: 25 pages, 10 figures
In addition to being crucial to the establishment of archaeological chronologies, radiocarbon dating is vital to the establishment of time lines for many Holocene and late Pleistocene palaeoclimatic studies and palaeoenvironmental re- constructions. The calibration curves necessary to map radiocarbon to calendar ages were originally estimated using only measurements on known age tree-rings. More recently, however, the types of records available for calibration have diversified and a large group of scientists (known as the IntCal Working Group|IWG)
with a wide range of backgrounds has come together to create internationally-agreed estimates of the calibration curves. In 2002, Caitlin Buck was recruited to the IWG and asked to oer advice on statistical methods for curve construction. In collaboration with Paul Blackwell, she devised a tailor-made Bayesian curve estimation method which was adopted by the IWG for making all of the
2004 internationally-agreed radiocarbon calibration curve estimates. This paper reports on that work and on the on-going work that will eventually provide models, methods and software for rolling updates to the curve estimates.
Reply to Blockley, Donahue & Pollard - Volume 74 Issue 283 - R. A. Housley, C. S. Gamble, P. Pettitt
Various methods of analysing the dating of the late Glacial suggest various interpretations. Here, in answer to a paper from 1997, radiocarbon dates are calibrated and used to reconsider the dating of this contentious period.
In this paper we describe newly launched software for on-line Bayesian calibration of archaeological radiocarbon determinations. The software is known as BCal and we invite members of the world-wide archaeological research community to use it should they so wish. All that is required to gain access to the software is a computer connected to the Internet with a modern World-wide Web browser (of the sort you are probably using to read this). BCal does not require access to any additional 'Plug-ins' on your machine. Since the computations needed to obtain the calibrations are undertaken on the BCal server, if you have enough computer power to run your World-wide Web browser you have enough power to use BCal.
Archaeological syntheses of western Ecuadorian prehistory have been hampered by a lack of reliable absolute chronologies and detailed cultural sequences for many key areas, one of which is northern Manabí Province, known principally as the territory of the Jama-Coaque cultural tradition. This study presents a seven-phase cultural sequence for the Jama River valley of northern Manabí that spans over 3,600 calendar years. A statistical model relating the successive archaeological phases is established, based on prior knowledge of the stratigraphy and ceramic seriation from key archaeological sites throughout the valley. A Bayesian statistical approach is then employed to calibrate 37 radiocarbon determinations for the purpose of estimating calendar dates for the limits of these phases. Apart from its contribution to the prehistory of a poorly studied area, the analysis illustrates the value of a probabilistic Bayesian approach to radiocarbon calibration, especially when the determinations relate to archaeologically predefined phases. It also demonstrates the dangers of uncritically applying generalized periodization schemes to specific sequences of historical development and highlights the need for reassessing Ecuadorian chronology through more precise interregional correlations.
The paper presents and analyses 46 new radiocarbon measurements undertaken at the Oxford Radiocarbon Accelerator Unit with the aim of critically evaluating the existing chronology for Bronze Age metalwork. Samples chosen, from both old museum collections and more recent finds, were all organics in immediate physical contact with various types of bronze object; indeed the great majority were in direct functional association. Contextual integrity was further monitored by the identification of wood species and the estimation of growth stage, which was found consistently to be modest. The scientific procedures employed allowed the generation of dates with good precision and cross-referenced through control samples to the dendrochronological master curves.
Integrating spatial and temporal information from the Late Glacial human reoccupation of North Western Europe
- P G C E Blackwell
- Buck
BLACKWELL, P.G. & C.E. BUCK. 2001. Integrating
spatial and temporal information from the Late
Glacial human reoccupation of North Western
Europe. Department of Probability and Statistics
Research Report 508/01, University of Sheffield.