Radiocarbon Dating and Egyptian Chronology—From the “Curve of Knowns” to Bayesian Modeling
Abstract and Keywords
Radiocarbon dating has become a standard dating method in archaeology almost all over the world. However, in the field of Egyptology and Near Eastern archaeology, the method is still not fully appreciated. Recent years have seen several major radiocarbon projects addressing Egyptian archaeology and chronology that have led to an intensified discussion regarding the application of radiocarbon dating within the field of Egyptology. This chapter reviews the contribution of radiocarbon dating to the discipline of Egyptology, discusses state-of-the-art applications and their impact on archaeological as well as chronological questions, and presents open questions that will be addressed in the years to come.
Egyptology stood at the very beginning of radiocarbon dating, because it was the historical chronology of Egypt that was used to prove the method and its applicability. Nevertheless, Egyptologists and archaeologists working in Egypt were, and many still are, very reluctant to acknowledge the value of the radiocarbon dating method for testing and refining the historical chronology of Egypt, and radiocarbon’s potential for setting out a scientific chronological framework not only for the Nile Valley itself but also for Egypt’s neighboring civilizations.
This chapter outlines the history of radiocarbon dating within the field of Egyptology, summarizes current state-of-the-art assessments of the historical chronology based on radiocarbon data, and discusses open questions that still need to be answered. This contribution is not intended to give any clear-cut answers to many of these issues, and it will not argue for or against some of the current discussions (despite the fact that the author has done so in other publications). Instead, this article is intended to provide a concise overview of the topic and, by supplying an extensive list of references, to serve as a guideline for the reader that hopefully is of help for reaching his or her own conclusions.
The Egyptian Historical Chronology
Before we can discuss the history of radiocarbon dating and its implications for Egyptology, we have to address a few issues regarding the very backbone of the history of the Nile Valley, the historical chronology of Egypt.
The historical chronology of Egypt is basically an interpretation of a complicated network of interlocked data, such as king lists, genealogical information, astronomical observations, and similar sources. Absolute (calendar) dates are mainly derived from so-called dead reckoning (calculating reign lengths backward from an assumed fixed point in time) or from astronomical observations, such as Sothic or lunar data (see in general Hornung, Krauss, and Warburton 2006; for more recent assessments, Schneider 2008; Schneider 2010; Aston 2012/2013). The textual sources, their interpretation, and the historical reconstructions based upon them, have been summarized several times in the recent literature (for recent assessments, see Kitchen 2013). It is important to stress, however, that using this system does mean that the beginnings and ends of reigns of certain kings and dynasties can be expressed in absolute calendar terms. The historical chronology of Egypt is a political chronology, and as such it is a priori independent from archaeological phases and sites’ stratigraphies, material culture such as pottery, or scientific dating approaches, that is, radiocarbon dating.
For a long time, the Egyptian historical chronology was the sole chronological reference system not only for the Nile Valley itself but also for the Bronze and Iron Age eastern Mediterranean basin. It was indeed the backbone of history, especially during the second and much of the first millennium BC. Before the advent of radiocarbon dating, absolute dates for the local relative chronological sequence of the southern and central Levant (modern-day Israel, the Palestinian territories, Jordan, and Lebanon) were heavily dependent on the Egyptian historical chronology, and also the relative chronological sequences for Middle and Late Bronze Age Cyprus were linked to the historical chronology of the Nile Valley. Even much of the Aegean Bronze Age chronology was linked to, and dated via, the Egyptian historical chronology. Research in the northern Levant and (eastern) Anatolia, on the other hand, was mainly oriented toward Mesopotamia, and the Mesopotamian historical chronology (with its intrinsic debates on “High, Middle, and Low”) was used first and foremost for interregional chronological synchronization.
Although the method of radiocarbon dating was developed already in the late 1940s, the method is still not fully appreciated in the field of Egyptology today. Erik Hornung, in the introduction to the handbook Ancient Egyptian Chronology simply stated: “For the Dynastic period this procedure is, however, neither sufficiently reliable nor sufficiently precise” (Hornung 2006, 12). Several reasons can be named for explaining this reservation. Although there were always different interpretations of the Egyptian chronology available in the scholarly literature, absolute dates proposed for kings and dynasties seemed to be far more precise than any probability distributions of calibrated radiocarbon data. Also, for studying Egyptian archaeology and history, the (relative) chronological system of kings and dynasties was sufficient, as it put texts, archaeological contexts, material culture, and architecture in a relative chronological order, and one was able to relate events happening, for example, in the Nile Delta, with events going on in Upper Egypt, by using the same reference system.
Also for interregional studies, absolute dates were less important than relative synchronization. In the words of Philip Betancourt, who wrote extensively on the much-discussed issue of the Minoan eruption of Santorini in the early Late Bronze Age and its relation to the Egyptian historical chronology: “The problem is that the discovery of the absolute dates is not as important as the question of the relative chronology. For historical conclusions, moving an event a hundred years forward or back in time is not as important at our present level of knowledge as understanding its relevance to other events from approximately the same time” (Betancourt 1998, 295). Indeed, it was the question of interregional chronological synchronization of the Santorini eruption with Egypt and the ancient Near East that fueled the most recent and most comprehensive application of radiocarbon on the Egyptian historical chronology that was published by Christopher Bronk Ramsey, Michael W. Dee, and colleagues and that was recently further developed by Sturt W. Manning (Bronk Ramsey et al. 2010; Shortland and Bronk Ramsey 2013; Manning 2014).
But while state-of-the-art application of radiocarbon dating and Bayesian modeling are able to provide essential contributions to, and refinements of, Egyptian historical chronology, it was in fact the Egyptian historical chronology that stood at the beginning of the development of the method of radiocarbon dating.
Libby, the Curve of Knowns, and Egyptian Chronology
On December 23, 1949, the journal Science published the groundbreaking paper by James R. Arnold and Willard F. Libby that proved the applicability of the radiocarbon dating method. The title of the paper was “Age Determinations by Radiocarbon Content: Checks with Samples of Known Age” (Arnold and Libby 1949). After several years of working in secrecy at the University of Chicago and overcoming the reluctance of museum directors against destructive analysis of archaeological objects, Arnold and Libby were able to publish the first concise results. The authors reported measurements of six different samples, which—as was indicated in the title of the paper—were “samples of known age.”
Four of these samples were archaeological finds, one from Turkey (Tell Tayinat) and three from Egypt. The expected ages of these samples were determined according to the Egyptian historical chronology and were regarded to be beyond reasonable doubt. The very first sample that was measured (C-1) was a piece of wood from the tomb of Djoser at Saqqara provided by the Metropolitan Museum of Art in New York. Additional samples came from a mummiform coffin from the Oriental Institute of the University of Chicago dated to the Ptolemaic period, from the funerary boat of Senwosret III from the Chicago Natural History Museum, and from the tomb of Sneferu at Meydum from the University of Pennsylvania Museum in Philadelphia (see also Libby 1980 for the early history of radiocarbon dating). All these samples were dated according to the historical chronology of Egypt and compared to the results of the scientific analysis of the radiocarbon content. The authors concluded: “The agreement between prediction and observation is seen to be satisfactory” (Arnold and Libby 1949, 679). The Egyptian historical chronology proved the underlying hypothesis and the applicability of radiocarbon dating.
The method of radiocarbon dating has been described in many articles and handbooks over the past 60 years in great detail (for detailed explanations, see, e.g., Bowman 1995; Bronk Ramsey 2008; Taylor and Bar-Yosef 2014). For this chapter we will focus on a brief overview in order to facilitate the understanding of current discussions in the field.
The element carbon (C) consists of three isotopes, 12C and 13C, which are both stable, and 14C, which is radioactive and decays according to a known half-life of c. 5730 years. Radiocarbon (14C) is produced in the upper atmosphere by a reaction of thermal neutrons with atmospheric nitrogen (14N). 14C oxidizes to 14CO2 (carbon dioxide), gets mixed within the atmosphere, absorbed by plants through photosynthesis, and finally enters animals or humans by ingestion of plants. Once a human, an animal, or a plant dies and ceases exchanging carbon with its environment, no more radiocarbon is being taken up; thus, the decaying radiocarbon is not replaced by new radiocarbon from the environment. Whereas 14C decays over time, the amount of 12C remains constant. The less 14C in relation to 12C is found in a sample, the older it is, as more time elapsed from the point of time when the sample stopped exchanging carbon with the environment. This is the underlying principle of radiocarbon dating (see also Bronk Ramsey 2008).
However, the atmospheric production of radiocarbon was not constant throughout time. Variations do exist due to changes in the cosmic ray influx and to variations in the Earth’s magnetic field. These variations result in varying ratios of 12C/14C in the atmosphere throughout time, inherently affecting the 12C/14C ratio of living organisms. Consequently, their calculated age as determined by radiocarbon dating is affected by the atmospheric carbon ratio at time of death. The respective atmospheric 12C/14C ratios of given calendar years have been measured by analyzing tree-ring sequences of known age, that is, sequences that continue up to present time. These measurements of tree rings allow the radiocarbon date of a given organic matter to be calibrated, meaning that the radiocarbon age of a given organic sample is compared to the record of 12C/14C ratios as determined by tree-ring sequences (the calibration curve). The rising and falling 12C/14C ratios of the atmosphere result in the wiggly shape of the calibration curve and translate a single radiocarbon year into a range of possible calendar years (Stuiver and Suess 1966). Calibration curves get updated regularly, and slight changes might also lead to a shift of absolute calendar dates of already measured samples. The most up-to-date radiocarbon calibration curve is INTCAL13 (Reimer et al. 2013).
Due to inherent inaccuracies of the measurement process and the irregular shape of the calibration curve, radiocarbon dates are expressed as probability distributions on the absolute timeline, usually ranging over a century or more. It should be kept in mind that a given radiocarbon date does not automatically date the archaeological context, but only the point in time when the organic sample ceased exchanging carbon with its environment (i.e., the date of the death of the organism). Depending on the type of context and the type of sample, the probability distribution can either be regarded as a terminus post quem (e.g., when dating charcoal from timbers) or an approximate terminus ad quem (e.g., when dealing with cereal grains found in a storage jar in a destruction layer) for a given context or event. To produce meaningful results, it is of utmost importance that archaeologists and radiocarbon specialists work closely together. Input from both sides is needed to create reliable sequences of radiocarbon dates that can eventually lead to a radiocarbon-backed chronological framework.
Figure 1 shows a calibrated radiocarbon date. The sample (pomegranate seeds) comes from a secondary interment in a 5th Dynasty tomb at Saqqara, originally excavated by the Prussian expedition directed by Carl Richard Lepsius in the mid-nineteenth century AD (Lepsius 1849–1859, Textband I, 165–170). According to the pottery, the secondary burial most likely dates to the 18th Dynasty. Based on the context (tomb) and the sample (short-lived cultigen, most likely interred as tomb offering), it could be expected that a radiocarbon date of the pomegranate seed should be representative for the time of the burial. Objects of this burial were located in the Egyptian Museum Berlin, and a sample of pomegranate seeds was submitted to the Vienna Environmental Research Accelerator for radiocarbon measurement (Figure 1). The calibrated result falls between 1498 and 1437 BC at 68.2% confidence and between 1595 and 1589 or 1532 and 1407 BC at 95.4% confidence, being thus in agreement with the dating assessment based on the associated pottery and grave goods (see also Höflmayer et al. 2013).
Radiocarbon Dating in Egyptology
Soon after the first publications of radiocarbon dates for ancient Egypt, potential implications for the historical chronology were discussed. In 1963, Willard F. Libby noted some discrepancies between radiocarbon dating and historical dates for third millennium BC and earlier periods in Egypt. For this period, radiocarbon, in general, provided dates that were lower than anticipated by Egyptologists. Libby concluded that “the data suggest that the Egyptian historical dates beyond 4000 years ago may be somewhat too old, perhaps five centuries too old at 5000 years ago, with decrease in the error to 0 at 4000 years ago” (Libby 1963, 216). Egyptologists and Egyptian archaeologists however, hesitated to take up on the new proposed dates, although in general without questioning the method of radiocarbon dating as such. “It is not of course a question of doubting the basic soundness of the radiocarbon method. The agreement with ‘historical’ dates back to 2000 BC and the generally satisfactory sequence of dates before that dispose of such doubts,” H. S. Smith pointed out 1964 (Smith 1964, 36). However, Smith continued that at that time the amount of dates was not big enough to be entirely convincing. According to him, too many open questions, both in terms of radiocarbon dating (interlaboratory offsets, different half-lives, etc.) and in terms of historical chronology of the third millennium BC and earlier prohibited any far-reaching conclusions regarding the absolute date of the early periods of Egypt (Smith 1964).
In the 1960s it was discovered that radiocarbon dates need calibration (discussed earlier) to account for the variations of radiocarbon production throughout time, and as a consequence radiocarbon dates shifted in absolute terms also for ancient Egypt (Stuiver and Suess 1966). Due to the calibration process the error margin of the calculated calendar date for a given sample often increased considerably. Therefore, Egyptologists remained skeptical, particularly regarding the applicability of the calibration curve that was initially based on tree-ring sequences of bristlecone pine from the White Mountains in California, on radiocarbon dates from ancient Egypt. In fact, H. McKerrell argued that one should construct an alternative calibration curve based on the Egyptian historical chronology to correct the results of samples in conflict with values expected by Egyptologists and archaeologists (McKerrell 1975), a claim that of course was rejected in the field of radiocarbon dating (Clark 1978).
Aside from questions about which calibration curve should be used for Egyptian samples, Egyptologists in general remained very skeptical about the use of the method for the field. I. E. S. Edwards pointed out that he could not “pretend that 14C has yet made any actual impact on our reconstruction of Egyptian chronology” (Edwards 1970, 11), and Ronald Long came to the conclusion that radiocarbon dating was not a suitable tool for refining Egyptian chronology where “dating is facilitated by other more precise methods” (Long 1976, 35). At that time radiocarbon dating still was extremely expensive and required substantial sample sizes, so that Egyptologists and archaeologists were hesitant to take on this new dating method because of financial and conservational issues. However, that absolute calendar dates for the historical chronology as reconstructed based on the interpretation of written sources were for the first time (albeit with considerable error margins) approximately confirmed was rarely acknowledged. Most Egyptologists expected that at best radiocarbon dating would tell them something that they already knew. “If a C14 date supports our theories, we put it in the main text. If it does not entirely contradict them, we put it in a foot-note. And if it is completely ‘out of date,’ we just drop it” (Säve-Söderbergh and Olsson 1970, 35).
For a long time, no focused projects had been undertaken in trying to come up with a radiocarbon-backed chronology for ancient Egypt. Scholars usually compiled all the dates published in the relevant literature and came to similar conclusions; that is, for many of the published samples, the archaeological context was at least dubious if not highly questionable: “in too many cases samples have been chosen which cannot be archaeologically dated with sufficient certainty or within narrow margins” (Säve-Söderbergh and Olsson 1970, 47). In 1971 Robin Derricourt published an impressive amount of data not only for Egypt but also for Nubia, the Sudan, the Cyrenaica, Libya, Chad, and Ethiopia in order to study interregional comparison and chronological synchronization. Derricourt also used radiocarbon data to provide possible links between the cultural dataset and climatic development (Derricourt 1971). An updated compilation of Egyptian radiocarbon dates was published in 1976 by Ronald Long (Long 1976).
That current chronological frameworks may be changed based inter alia on the results of radiocarbon measurements was for the first time suggested in 1979 by Anatolian archaeologist James Mellaart. He argued that the then available set of radiocarbon dates for ancient Egypt would fit a higher chronology, and he proposed to raise absolute calendar dates for the historical chronology accordingly (Mellaart 1979). However, his suggestion has been fiercely rejected, not only by Egyptologists but also by Biblical archaeologists (Kemp 1980; Weinstein 1980).
The available radiocarbon dataset was again reviewed by Ian Shaw in 1985, who, for the first time, used the Irish oak calibration curve that had become available just a few years earlier (Pearson, Pilcher, and Baillie 1983; Shaw 1985). However, also Shaw thought that for many discrepancies between radiocarbon date and expected date, according to the Egyptian historical chronology, the actual error might be sought for in the methods of collection and analysis (Shaw 1985, 298). In the mid-1980s the conclusion generally accepted in the field still was that “the value of these routine radiocarbon dates is minimal” (Shaw 1985, 304).
Things slowly began to change in the mid- to late 1980s. A paper published in the journal Antiquity in 1987 by Fekri A. Hassan and Steven W. Robinson acknowledged that the Egyptian historical chronology stood at the beginning of radiocarbon dating, but that “with this paper the reverse process begins: verifying and correcting the conventional chronology for Egypt and neighbouring regions by calibrated radiocarbon” (Hassan and Robinson 1987, 119). Hassan and Robinson not only tried to base the Egyptian historical chronology on radiocarbon data but also compared the radiocarbon record of Egypt with that of the Levant; thus, instead of doubtful archaeological synchronisms, the authors began to reconstruct a coherent framework based on radiocarbon evidence, a process that is still ongoing.
In 2001, Georges Bonani and colleagues reported on the first systematic radiocarbon dating project that addressed the historical chronology of Egypt (Bonani et al. 2001). In the course of this project that was carried out between 1984 and 1995, more than 450 samples dating to the Old and Middle Kingdoms were analyzed. However, although all the results for the individual dates were published, unfortunately the project did not come up with any conclusions and therefore had a very limited impact on Egyptology.
In the seminal work on Ancient Egyptian Chronology edited by Erik Hornung, Rolf Krauss, and David A. Warburton and published in 2006 (Hornung, Krauss, and Warburton 2006), despite the skeptical view of the editors (see Hornung’s earlier statement), a special chapter was devoted to radiocarbon that was authored by Sturt W. Manning (Manning 2006). Still the method stood on the fringes of the discipline of Egyptology, even in a volume that was especially devoted to chronology. Sturt Manning noted that far too few good examples of modern research programs existed that provided transparent, good, and useful data that actually could have helped to refine the Egyptian historical chronology. And thus the author concluded: “High quality radiocarbon dating offers an important but as yet not fully exploited resource for Egyptology” (Manning 2006, 352).
Although up to the mid-2000s radiocarbon dating for Dynastic Egypt was almost never carried out in a systematic way with clear research questions, sampling strategy, and interpretation, since then, results of two independent projects set the radiocarbon record for Egypt on new grounds. The first project was entitled “Radiocarbon Dating and the Egyptian Historical Chronology” and was carried out by Christopher Bronk Ramsey, Michael W. Dee, and colleagues at the University of Oxford (Bronk Ramsey et al. 2010; Shortland and Bronk Ramsey 2013). In general, this project provided results that are in agreement with the Egyptian historical chronology. The second project was SCIEM 2000 (“The Synchronization of Civilizations in the Eastern Mediterranean in the Second Millennium BC”), directed by Manfred Bietak and carried out at the Austrian Academy of Sciences. Although this project primarily focused on establishing chronological synchronisms between Egypt, the ancient Near East, Cyprus, and the Aegean based on archaeological data, especially the first appearances of key-pottery wares (see Bietak 2013), it also included a subproject on radiocarbon dating, directed by Walter Kutschera. This subproject produced the most substantial sequence of radiocarbon dates that is currently available from a single site in Egypt, from Tell el-Dabca, ancient Avaris, in the eastern Nile Delta (Kutschera et al. 2012). Although the Oxford project provided dates that were in agreement with historical estimates, radiocarbon dates for Tell el-Dabca were in gross conflict with the archaeological/historical date estimations of the excavator. Although at this time the question of what leads to this divergence cannot be conclusively answered, several lines of evidence seem to suggest that a major redating of archaeological phases and synchronisms within Egypt and the Near East might be in order (see Manning et al. 2014; Höflmayer 2015; Höflmayer forthcoming).
The Oxford Project
The most comprehensive approach to radiocarbon dating the Egyptian historical chronology was the Oxford-based project directed by Christopher Bronk Ramsey published as a paper in the journal Science in 2010 and—with much more additional data and also including other approaches to chronology and radiocarbon data—in an edited volume in 2013 (Bronk Ramsey et al. 2010; Shortland and Bronk Ramsey 2013).
As the editors pointed out in their preface, “the research project that provided the impetus to this book, was then primarily intended as a check of whether radiocarbon dating ‘worked’ in Ancient Egypt, and discovering if not, why not” (Bronk Ramsey and Shortland 2013, v). This project was the first one to systematically employ Bayesian analysis of large sets of radiocarbon dates and historical constraints instead of comparing individual calibrated radiocarbon determinations with absolute dates proposed for the Egyptian historical chronology. For this project more than 200 new high-precision radiocarbon measurements have been conducted on short-lived samples from secure archaeological contexts, which had been studied and dated by Joanne Rowland (now Free University of Berlin). Samples had to be retrieved from museum collections all over the world, because it was not possible to export samples for destructive analysis from Egypt.
Although the probability distribution of an individual calibration of a radiocarbon determination can span over a century or even more (one of the reasons why radiocarbon dating was so often considered as irrelevant to Egyptology), additional information can be employed in order to increase precision and to construct models that can be compared with historical estimates and that can be used as a chronological framework for the respective historical period. Bayesian analysis allows taking additional information such as stratigraphy, or the known relative sequence of kings and so on into account. Such information is called prior information, as it is derived from sources other than, and prior to, radiocarbon analysis in the laboratory (Buck et al. 1991; Weninger et al. 2006; Bronk Ramsey 2009). Based on this prior information and the radiocarbon measurements, a posterior probability for each individual sample (and each additional event in the model, such as transitions between phases) can be calculated.
The Oxford project also investigated the accuracy of radiocarbon dating in Egypt on samples of known age. From the University of Oxford Herbaria and the Natural History Museum, London, 66 samples of short-lived plant materials that have been collected from Egypt between c. 1700 and 1900 AD (prior to the building of the Aswan dam and the subsequent massive changes for the local environment) were selected, where the calendar year of the collection was known. Results were calibrated against the INTCAL09 calibration curve and compared to the known collection date. An average difference between radiocarbon measurement and expected results of 19 ± 5 radiocarbon years has been determined, most probably due to a local growing season effect, relating to the annual variation in atmospheric radiocarbon activity. Plants growing in the early spring absorb CO2 of the annual low, whereas plants growing in late spring or summer (as with European trees from which the calibration curve is based) absorb from the annual high. This difference in the growing season between Egypt and Europe is most probably the reason for the slightly elevated radiocarbon dates for samples of known age in Egypt (Dee et al. 2010; Dee 2013d). It is also important to note that this offset was accounted for in the models published.
Three distinct chronological models were constructed, for the Old, Middle, and New Kingdom. For the New Kingdom, 128 new radiocarbon dates from short-lived plant materials were used. In total, six models were run using different prior information. The most important one was the “high” model based on reign lengths, as suggested by Ian Shaw (Shaw 2000) and the “low” model based on the reign lengths as proposed by the editors of the volume on Ancient Egyptian Chronology, Erik Hornung, Rolf Krauss, and David A. Warburton (Hornung, Krauss, and Warburton 2006). Prior information included the sequence of kings and their respective reign lengths. Where there are different opinions on the respective length of reigns, several models have been created. However, it is important to note that by incorporating the reign lengths within the model, it is not possible to draw conclusions on reign lengths from the outcomes of the models (because these are already incorporated). The models tell us that (a) radiocarbon dating is in agreement with current estimates of a high Egyptian chronology and that (b) prior information is compatible with the radiocarbon determinations. As Michael Dee pointed out: “By including Interval constraints at the outset, the approach taken here waived the right to draw conclusions about reign lengths from the results. In many ways, this reduced the task to one of positioning the relative chronology on the absolute time-scale” (Dee 2013b, 70).
For the Middle Kingdom, 42 new samples have been measured and four Bayesian models have been created, based on the high chronology (as published in Shaw 2000), the low chronology based on Hornung, Krauss, and Warburton, with additional models based on Kenneth Kitchen and Ian Shaw, where all outliers were eliminated (Ian Shaw 2000; Kitchen 2000; Hornung, Krauss, and Warburton 2006; Dee 2013a). The radiocarbon models are consistent with the high Middle Kingdom chronology and challenge the low estimates of Hornung, Krauss, and Warburton, even when the reign lengths of the latter scholars are used as prior information for the Middle Kingdom model. Radiocarbon data are thus consistent with the Sothic date of Berlin Papyrus 10012A dated on paleographic grounds to the reign of Senwosret III (for a recent skeptical opinion on using this Sothic date, see Schneider 2008, 280–285).
For the Old Kingdom only 17 new samples could be measured and especially the 5th to 8th Dynasties lacked suitable sample material (Dee 2013c). Again, several models were created, their prior information deriving from Ian Shaw (2000), Erik Hornung, Rolf Krauss, and David Warburton (2006) and Kenneth Kitchen (2000). Whereas the radiocarbon model finds the high chronology in good agreement with the scientific results, there is a slight offset between radiocarbon dating and historical estimates for the 5th and 6th Dynasties.
The Oxford project showed conclusively that radiocarbon dating combined with a Bayesian statistical approach provides results that are generally in agreement with calendar dates from historical estimations based on the interpretation of texts. Although recent reanalysis by Sturt Manning according to higher reign lengths as proposed by Aston led to a higher start date of the New Kingdom around 1575 BC (Manning 2014), the difference is a few decades.
Radiocarbon Dating and Tell el-Dabca
At the same time, the radiocarbon sequence for the site of Tell el-Dabca (ancient Avaris) in the eastern Nile Delta provided results that are in gross conflict with calendar dates proposed by the excavator (Kutschera et al. 2012). This difference of about 120 years is of considerable significance not only for the site itself but also for our understanding of the history and development of Egyptian history and cultural development during the Second Intermediate Period and early New Kingdom. Indeed, many open questions regarding chronology and absolute dates center on this site and its links with the historical chronology. Because the site is of utmost relevance, not only for the history of the Egyptian Second Intermediate Period but also for linking the relative chronological sequences of the Levant, Cyprus, and, partly, of the Aegean to Egypt, we will discuss the site and the results of the radiocarbon project in more detail.
Tell el-Dabca is located on the Pelusiac branch of the Nile in the eastern Delta, approximately 100 km northeast of Cairo and 45 km west of the Suez Canal (Bietak 1975; Bietak 1996). Excavations were conducted in several areas: most notably Area A/II, where a cemetery and temple of the Middle Bronze Age and settlement layers have been unearthed; Area F/I with a planned settlement of the early Middle Kingdom, a settlement, palatial building, and necropolis of the late Middle Kingdom and 13th Dynasty; Area F/II with another palatial complex attributed to the Hyksos ruler Khayan; Area R/I with a Middle Kingdom temple; and Area H with a palace compound dated to the Thutmosid period (see Bietak 2013 with references therein). Overall the site spans a stratigraphy of about 600 years (start of the Middle Kingdom to Amenhotep II, see Figure 2).
However, the stratigraphy of the site is in fact a compilation of several different stratigraphies of the respective excavation areas. These distinct areas have been synchronized on the basis of “pottery seriation and recurring architectural features, such as building materials, house types, tomb types plus a combination of all of them” (Bietak 2013, 78). Bietak claims that “the [ceramic] percentages were assessed on large quantities of authentic stratigraphic settlement material at Tell el-Dabca and then compared with the material from other stratigraphies at other parts of the same site, reaching further back in time, whilst showing a significant overlap” (Bietak 2013, 78).
The stratigraphy of the site allows for assessing the development of the stratified material culture (most notably pottery) that has been found in the distinct strata. To relate the excavated archaeological remains to the history of the Nile Valley, the local stratigraphy had to be synchronized with the Egyptian historical chronology.
According to the excavator, four so-called datum lines are of prime importance for this task, the 5th year of Senwosret III mentioned on a stela linked to the construction of the temple of cEzbet Rushdi at the start of Str. K, the construction of a palatial building attributed to Khayan during late Str. E/1 and early D/3, the conquest of Avaris by Ahmose at the end of Str. D/2, and scarabs with kings’ names (the youngest being Amenhotep II) from Str. C/2 (Bietak 2013). In the beginning, only the datum lines from cEzbet Rushdi (5th year of Senwosret III and Str. K) and the fall of Avaris (transition from Str. D/2 to D/1) were available for linking the stratigraphy of the site to the Egyptian historical chronology (the so-called palace of Khayan was only excavated from 2006 onward). Between these two datum lines, the 11 existing strata of the “master-stratigraphy” were evenly distributed, resulting in an average of 30 years per stratum (Bietak 2002, 31; Bietak 2013, 81).
A substantial sequence of radiocarbon evidence from the site of Tell el-Dabca, however, challenges the absolute calendar dates for the site’s stratigraphy as put forward by the excavator. In the framework of the SCIEM 2000 project, more than 40 short-lived samples from the site of Tell el-Dabca have been radiocarbon dated at the Vienna Environmental Research Accelerator and the Oxford Radiocarbon Accelerator Unit (Kutschera et al. 2012). Samples have been obtained from Str. C/2 to H, and thus should cover the time from the late 12th Dynasty down to the Thutmosid period. Additional samples come from Strata M to N (dated to the early 12th Dynasty). Str. I to L are not represented in the dataset.
A Bayesian probability approach was used to refine the individual calibrations. It was assumed that the short-lived samples are representative for their respective find contexts and that archaeological phases are in the correct chronological order. However, the sequence produces results that are in gross conflict with the dates proposed by the excavator. In average, radiocarbon dates are about 120 years higher than dates for the site’s stratigraphy based on the assumed datum lines with the Egyptian historical chronology (Figure 3). These results challenge the validity of the proposed datum lines and require a rigorous reanalysis of the site’s stratigraphy and dating before reaching a final verdict (see Manning et al. 2014; Höflmayer 2015; Höflmayer, forthcoming, for some preliminary conclusions on this issue, but cf. also Bietak 2013 for a defense of the stratigraphy and its dating).
If the high radiocarbon dates for Tell el-Dabca were to be accepted, much of the site’s stratigraphy would have to be shifted upward, while at the same time the Egyptian historical chronology only has limited flexibility in the amount of some three to four decades, for example, for the beginning of the New Kingdom. If Tell el-Dabca had to be redated, also the absolute calendar dates for the relative sequences of the Middle and early Late Bronze Ages of the Levant would have to be adjusted, because much depends on the archaeological synchronisms with Tell el-Dabca. Indeed, preliminary analysis of available radiocarbon dates from the Levant (Tell el-Burak, Lebanon, and Tel Ifshar, Israel) point to similar high dates (Höflmayer 2015).
Conclusions and Future Prospects
For a long time, Egyptology and radiocarbon dating have suffered an uneasy relationship. In the beginning, the historical chronology of Egypt was used to prove the applicability of the radiocarbon method, and for a long time Egyptologists were hesitant to take up this new technique due to larger error margins than what the traditional historical chronology could (seemingly) offer. But due to continued technical progress, increased measurement precision, and new approaches such as Bayesian statistics, radiocarbon dating today can help to test and refine the historical chronology of the Nile Valley. However, Egyptologists and archaeologists should be aware that—as always in science and the humanities—there will never be a final verdict, for example, of when the New Kingdom started. Every chronological conclusion has to be understood as preliminary, because new finds and new radiocarbon determinations might challenge earlier results.
The great benefit of radiocarbon dating is that organic remains can be dated independently in different regions using the same method. We are no longer dependent on archaeological synchronisms between, for example, the Nile Valley and the Levant, Cyprus, or the Aegean to create a coherent framework of, for example, the eastern Mediterranean. So far, absolute calendar dates for the Egyptian Old, Middle, and New Kingdoms can be based on radiocarbon dates. There are also a few sequences for the Early and Middle Bronze Ages of the Levant available that allow chronological synchronization based on radiocarbon dating (see, e.g., Regev et al. 2012; Marcus 2013; Höflmayer et al. 2014; Höflmayer 2015; Höflmayer et al. 2016a; Höflmayer et al. 2016b).
The special case of Tell el-Dabca with radiocarbon results that are about 120 years higher than dates proposed by the excavator will undoubtedly raise discussions for the years to come. If they were to be accepted, much of the Middle Bronze Age chronological framework for the Levant would have to be shifted upward. So far, radiocarbon results from sites in the Levant support the high dates from Tell el-Dabca.
Future work will fill current gaps and continue to refine the Egyptian chronology. It is hoped that the appeal once expressed by Sturt Manning will indeed be heard in our discipline: “radiocarbon dating should become the friend of Egyptologists” (Manning 2006, 354).
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