Old Sherds, New Science

Hershel Shanks’s First Person in the May/June 2013 issue of BAR

The Biblical Archaeology Society (BAS) has recently published a must-read for dig directors with the imposing and somewhat intimidating title Cyber-Archaeology in the Holy Land—The Future of the Past (available online for free).a It is written by Tom Levy and his team from the University of California, San Diego,1 who have been excavating at the Edomite copper-mining site in Faynan, Jordan, since 1997.b According to the Bible, the site was visited by the Israelites on their Exodus journey from Egypt (Numbers 33:43).

We still dig the old-fashioned way, Levy tells us, “like our 19th-century predecessors with shovels, picks, trowels, dustpans, toothbrushes and so on. What is different is the use of digital tools to record data—and lots of it. In short, the way we collect and analyze the data that we recover is completely changing. Cyber-archaeology faces the challenges of quickly and accurately collecting masses of archaeological data, visualizing it and sharing it with colleagues and the public. This process can be visualized with a four-part model that focuses on acquisition, curation, analysis and dissemination of data.”

The ubiquitous pieces of broken pottery—sherds—found at every archaeological site in the Near East have been used for dating the various archaeological strata since the days of Flinders Petrie. With cyber-archaeology that will change:

“Instead of relying on the traditional archaeological assumptions that are used to date pottery to a chronological period based on style, we decided to use a large number of high-precision radiocarbon dates anchored into the stratigraphy of the site with the best contextual/cultural data that cyber-archaeology can offer.”

But just when we thought science had solved our dating problems, we are stopped short.
 


 
Download the FREE eBook “Cyber-Archaeology in the Holy Land — The Future of the Past,” featuring the latest research on GPS, Light Detection and Ranging Laser Scanning, unmanned aerial drones, 3D artifact scans, CAVE visualization environments and much more.

For more cutting-edge archaeological technology, visit the BAS Archaeological Technology page.
 


 
The plenary speaker at last year’s annual meeting of ASOR, the leading American professional association of Near Eastern archaeologists,2 was one of the world’s most eminent archaeologists: Manfred Bietak of the University of Vienna. Dates used in Near Eastern archaeology are ultimately dependent on ancient Egyptian dates, and Bietak digs at the leading site in Egypt for determining these dates: Tell el-Daba, a harbor town in the Nile delta. His work is universally admired.

His talk was extremely technical but shocking in its way: He questioned the precision of much radiocarbon (carbon-14) dating! To be sure I quoted Bietak accurately, I asked him if I could have a copy of his talk. He replied that he spoke without a manuscript, but he sent me an article covering much of the same material, titled “Antagonisms in Historical and Radiocarbon Chronology,” that is to be published in a forthcoming volume.3

“In some circles” Bietak observed, it has “become a crime to cast doubt on the reliable accuracy of radiocarbon dating.” Bietak calls it “the present deadlock,” referring to the differences between the two systems of dating, one by pottery sherds and the other by carbon-14.

In short, after years of extremely careful work at Tell el-Daba and by comparing it with other sites all over the Mediterranean, Bietak has determined a chronology based on what he calls historical data (mainly pottery seriation), which significantly differs from the chronology produced by carbon-14 tests. The difference in dates that Bietak refers to amounts to about 80 years, roughly the same as that between the “minimalists” and “maximalists” in Israelite chronology.c The carbon-14 tests focus especially on the Iron Age, the period ascribed to the Israelite monarchy, where the approximately 80-year difference can be crucial—and very controversial. A “critical attitude toward radiocarbon dating,” Bietak tells us, “becomes a casus belli instead of reflecting if and where there could be complications.”
 


 
BAS Library Members Read “Glossary: How to Date a Cooking Pot” by John C. H. Laughlin and “Archaeological Views: Carbon 14—The Solution to Dating David and Solomon?” by Lily Singer-Avitz as they appeared in Biblical Archaeology Review.

Not a BAS Library member yet? Sign up today.
 


 
Bietak outlines the scientific difficulties in attaining accuracy and precision in carbon-14 dating. The difference (or offset) in what Bietak calls “historical” dating as opposed to “scientific” (i.e., radiocarbon) dating can be accounted for in a number of ways. For example, the radiocarbon in the atmosphere fluctuates in different growing seasons, especially in winter and summer wheat. Samples from sites near the sea, even the Dead Sea, give carbon-14 dates different from what we would expect. In short, differences in region and time of year could play a role in explaining the deviation of carbon-14 dates.

Moreover, “dates in radiocarbon chronology are in most cases obtained by combining the results of samples, even if spread over a considerable time. Outliers are usually omitted, although the decision of what is an outlier or not is sometimes strangely biased.”

And then there is the need in all cases for a Bayesian calibration of raw carbon-14 dates. I wasn’t sure I could explain this for a lay audience, so I asked Tom Higham, deputy director of the Oxford Radiocarbon Accelerator Unit in England. This is what he told me: The calibration allows for a more refined chronometry (dating) by using Bayesian statistical approaches. It is a statistical adjustment that allows the inclusion of archaeological evidence such as stratigraphic layers, other dating evidence from coins, volcanic ash, artifacts and the like, along with the calibrated radiocarbon ages. The modeling of these combined sets of data results in probability age estimates for specific archaeological events that are more robust and usually much more precise than those produced with single calibrated date ranges.

That’s about as plain and simple as you can get.

In short, radiocarbon does not offer a quick fix. We can’t stop dating pottery sherds “historically.”

As between Bietak’s dates based on his pottery chronology and the dates based on radiocarbon tests, I’ll put my money on Bietak.
 


 
Download the FREE eBook “Cyber-Archaeology in the Holy Land — The Future of the Past,” featuring the latest research on GPS, Light Detection and Ranging Laser Scanning, unmanned aerial drones, 3D artifact scans, CAVE visualization environments and much more.

For more cutting-edge archaeological technology, visit the BAS Archaeological Technology page.
 


 

Notes

1. Actually the Center of Interdisciplinary Science for Art, Architecture and Archaeology (CISA3) at the California Institute of Telecommunications and Information Technology (Calit2) at the University of California, San Diego.

2. The American Schools of Oriental Research (ASOR).

3. “Antagonisms in Historical and Radiocarbon Chronology,” in A.J. Shortland and C. Bronk Ramsey, eds., Radiocarbon and the Chronologies of Ancient Egypt (Oxford: Oxbow, 2013), pp. 78–110.

a. Thomas E. Levy, Neil G. Smith, Mohammad Najjar, Thomas A. DeFanti, Falko Kuester and Albert Yu-Min Lin, Cyber-Archaeology in the Holy Land—The Future of the Past (Washington, DC: Biblical Archaeology Society, 2012). www.biblicalarchaeology.org/cyber.

b. See Thomas E. Levy and Mohammad Najjar, “Edom and Copper,” BAR 32:04; Thomas E. Levy and Mohammad Najjar, “Condemned to the Mines,” BAR 37:06.

c. See Yosef Garfinkel, “The Birth and Death of Biblical Minimalism,” BAR 37:03; Philip R. Davies, “What Separates a Minimalist from a Maximalist? Not Much,” BAR 26:02; Hershel Shanks, “Face to Face: Biblical Minimalists Meet Their Challengers,” BAR 23:04.

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  • Lawrence says

    From my understanding, Carbon 14 dating works on the premise that all living animals (Humans included) when they die have a certain amount of carbon in them that decays at a uniform rate over time. The problem is that this isn’t so and from what I’ve read on the subject within the first six months of death 80% of carbon is lost.

    In 2005 a samlpe of rock that came into being after Mount St Helens erupted was sent to some of the top radiocarbon dating labs in the world. the dates given for the age of the rock was anything from 3 to 20 million years old, that was despite the fact that it only became ‘rock’ in 1986 and before that it was molten magma! Carbon 14 is based on a faulty premise

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