The city of Jerusalem, with a deep-time history spanning over 6000 y, is a sacred site for the world’s 3.8 billion people who follow the Abrahamic religions—Judaism, Christianity, and Islam. For more than 150 y, western and indigenous archaeologists have explored this ancient city as it was the capital of earliest Israel since the 10th century BCE when the Hebrew kings David and Solomon established Israel’s capital there (1, 2). Consequently, most archaeological field work in the city has focused on the Biblical period (ca 1200 to 586 BCE) rooted in the Hebrew Bible or Old Testament. To objectively investigate the relationship between sacred and ancient historical texts with the archaeological record, researchers need to apply digital methods to control the spatial context of archaeological finds (3) and high-precision radiocarbon and other absolute dating methods to measure temporal change (4). This applies globally to all historical archaeologies such as the Mahabharata (India), the Icelandic Sagas (Scandinavia), the Koran (Middle East), Homeric texts (Aegean), and more. While archaeologists have employed radiocarbon dating in the Middle East since it was invented in the late 1940s, it is puzzling that until the landmark study “Radiocarbon Chronology of Iron Age Jerusalem Reveals Calibration Offsets and Architectural Developments” (5), no systematic 14C dating project was carried out in Jerusalem. Here, we highlight the significance of the article and its role as a catalyst for stimulating more absolute dating and historical archaeology research, including methods that help mitigate challenges inherent to the use of 14C.
From a global perspective, the Jerusalem 14C project serves as a model for applying radiometric dating in contemporary excavations in existing ancient cities that are challenged by actively inhabited urban environments, modern and ancient conservation needs, high urban growth, working around utilities and infrastructure, environmental challenges, limited access and space, fragmented and disturbed contexts, public awareness and engagement, and time and cost constraints (6). The excavations take place in the densely populated Southeastern Ridge (known as the “City of David”) where the contemporary Palestinian neighborhood of Wadi Hilwa/Silwan is located. The 14C dating project (5) focused on some of the most significant areas where Iron Age remains have been exposed. Accordingly, only rare noninhabited open areas, some purchased by the Rothschild Foundation in the 19th century, have been the focus of excavations that have been contentious (7). Most important is the wealth of scientific data these excavations provide in relation to Biblical and other historical sources (8, 9). The radiocarbon samples come from some of the most important areas of the City of David. The Givati Parking Lot provides a unique opportunity for large contiguous excavations (0.5 hectare) on the densely settled ridge. Excavations beside the Gihon spring are near a late 8th–early 7th c. BCE Iron Age extensive rock-cut tunnel mentioned in the Hebrew Bible, where an inscription related to the Judean King Hezekiah (2 Kings 20:20) was found (10). Upslope from the spring, new excavations revealed important 10th c. BCE occupation and other temporal data. A hundred meters south of the spring, unique Iron Age domestic houses, initially excavated in the early 1970s, were resampled. These geographic areas on the ridge provide 14C samples uniquely suited to investigate the relationship between the archaeological record and ancient texts.
Since the early 2000s, researchers have employed Bayesian statistical methods for calibration (11) that use information from the specific context of the sample and data from the 14C calibration curve. When researchers have large numbers of radiocarbon dates, like the Jerusalem study (n = 103), the use of Bayesian analyses and the latest calibration software (currently IntCal20—https://www.intcal.org/data.html) increases the feasibility to relate the dates to historical events. Yet, for certain periods when the calibration curve has a “plateau”, achieving high dating resolution is challenging (12). The Jerusalem study covers the Hallstatt Plateau (13), resulting in calibrated age resolution of ±200 y for the period between ca. 800 and 400 BCE—a key period in the history of Jerusalem that includes its destruction by a major earthquake (8th c. BCE) and by the Babylonian army (early 6th c. BCE).
The Jerusalem 14C project attempted to overcome the Hallstatt Plateau problem by wiggle matching of multiple samples with the calibration curve, and by microarchaeology (14) and laboratory investigations, including processing 100 single tree rings from Bristlecone pine and Irish oak that were found in the excavations. The use of microarchaeology is state-of-the-art. Today, with the array of microarchaeology tools, more data and knowledge can be acquired by excavating less and focusing on retrieving more samples and tighter stratigraphic observations from smaller excavation areas utilizing digital recording tools.
Challenges posed by the Hallstatt Plateau and other issues with 14C dating can be further mitigated by the application of other absolute dating techniques that have become increasingly more accurate and precise in recent years, including archaeomagnetism. The latter is based on constant small-scale changes in the properties of the geomagnetic field. It has the advantage that data in the reference curves can be anchored according to known historical events, holding the potential for a higher-resolution dating than that of 14C in periods of plateaus in the calibration curve and, in some cases, even for periods for which the calibration curve is considered ideal (15). Recently, the properties of the geomagnetic field in Jerusalem in August 586 BCE were established (16), and this anchor was used to refine the date of construction of the Ishtar Gate of Babylon (17). Similarly, geomagnetic anchors for other historically known military campaigns and associated destruction events have been established for the Iron Age southern Levant (18). In turn, these data points were used to date fired archaeological contexts and artifacts, contributing to the resolution of chronological problems that could not be resolved by 14C alone (Fig. 1). Moving forward, archaeologists should apply a variety of complementary absolute dating methods to solve chronological problems.
Fig. 1.
Achieving high-resolution absolute dating in periods of plateaus in the radiocarbon calibration curve is challenging. Calibrated dates for the Biblical kingdom of Edom currently have at least 200-y ranges during the Hallstatt Plateau (Late Iron Age), frustrating attempts to correlate archaeological contexts with known historical events. For the same period in Jerusalem, multiple dates from tightly controlled stratigraphic contexts, together with Bayesian analysis and wiggle matching, yielded calibrated dates in the range of less than a decade and significant historical insights (5). Geomagnetic data for the region anchored in historical destruction events provide an additional potent tool to refine absolute dates in this period (18). Among recent examples is the dating of the construction of Ishtar Gate in Babylon to the later part of Nebuchadnezzar II’s reign, based on the observation that the field was weaker (purple star in the Upper diagram) than the field in Jerusalem in 586 BCE and the general trend of the curve (17). Radiocarbon calibration by OxCal (https://c14.arch.ox.ac.uk/oxcal.html) v.4.4.4. The geomagnetic intensity data are based on Vaknin et al. (18), where the key to color and symbols is provided.
The Jerusalem 14C project provides a catalyst for historical archaeologists around the world to interrogate the relationship between the archaeological record and sacred/ancient texts in challenging cultural heritage urban contexts.
Recent Iron Age radiocarbon data from ancient Israel’s neighbor, Edom in modern Jordan (19, 20), like the new Jerusalem suite of dates, constitute a large dataset (N = 162). While the Jerusalem study was able to identify calibration offsets to deal with the Hallstatt Plateau problem, Cook et al. (21) obtained precision on a piece of timber dating to 500 to 480 BCE of ±6 to 16 y. For Edom, we are unable to do so as we would need a dataset such as a tree ring series, a continuous stratigraphic segment or something robust in terms of historical tie-points to add to the model. We can achieve more dating accuracy for the Late Iron Age (IIB/C, ca. 900 to 586 BCE) if we factor in a new archaeointensity dataset from the southern Levant to our modeling (18). The growing application of different absolute dating methods in the region is creating a number of chronological anchors for ancient historical military campaigns and natural events such as the devastating mid-8th c. BCE earthquake reported in Biblical texts (Amos 1:1, 22) and identified in Jerusalem by ref. 5. While the majority of 14C dates (N = 154) from Edom show that the earliest kingdom complex society emerged in the hyper-arid copper production lowlands in the 11th to 9th c. BCE, by the late 9thc. BCE copper production ceased and, after a gap of about a century, sedentary occupation on the semiarid plateau edge started to emerge (Fig. 1). This represents a new phase of the Edomite kingdom with economy based on the Arabian trade and relations with Assyria following their military campaigns in the southern Levant (23).
In conclusion, the Jerusalem 14C project provides a catalyst for historical archaeologists around the world to interrogate the relationship between the archaeological record and sacred/ancient texts in challenging cultural heritage urban contexts. For Holocene historical archaeology, the integration of multiple absolute dating methods (e.g., dendrochronology, high precision radiocarbon dating, archaeomagnetic dating, OSL—Optical Stimulated Luminescence) and microarchaeology techniques (portable XRF—X-ray Fluorescence; Fourier Transform Infrared spectroscopy—FTIR; ancient DNA; microscopy, etc.), coupled with advances in information technology and digital archaeology will open new vistas of understanding ancient texts and the material cultural record.
Acknowledgments
Author contributions
T.E.L. and E.B.-Y. designed research; T.E.L., N.G.S., M.N., Y.V., and E.B.-Y. performed research; Y.V. and E.B.-Y. contributed new reagents/analytic tools; T.E.L., N.G.S., Y.V., and E.B.-Y. analyzed data; and T.E.L., N.G.S., Y.V., and E.B.-Y. wrote the paper.
Competing interests
The authors declare no competing interest.
Footnotes
See companion article, “Radiocarbon chronology of Iron Age Jerusalem reveals calibration offsets and architectural developments,” 10.1073/pnas.2321024121.
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