Tuesday, March 10, 2015

Radiometric Dating of the Gospel of Judas

Peter Kirby has put together an excellent survey of information on the 14C dating of the Gospel of Judas, here.  The whole issue is complicated, particularly for those without a firm grounding in the application of radiometric dating, but I can summarize the conundrum by saying that a National Geographic publication by Herbert Krosney suggested that the GJudas codex material could be assigned to 280 CE ±60 years, but then represented the results as all falling in the third century.  (Both are statements are problematic, but especially the second.)  This was unfortunate and created a great deal of confusion and speculation.  The Tchacos Codex would then be the earliest Coptic manuscript currently known!

Peter Kirby offers a number of learned insights, but in particular points out an important gross error on the part of Krosney.  Krosney did not understand how radiocarbon results should be “calibrated” against known radiocarbon evidence (tree rings), and instead simply subtracted his BP (“Before Present”) numbers from the year in which the results were produced (2005) to erroneously produce a series of numbers dating to the the third century.

The National Geographic Society granted the Arizona AMS laboratory permission to send me the actual results, and I am publishing an update on the dating of the Tchacos Codex based on the findings.  Again, it’s complicated, and I offer here only a summary.  Krosney made a number of errors, including simple typos.  This is a shame, because generally his two Judas books are well-executed.  In my forthcoming book chapter, I advance the theory of Peter Head, including the actual results from the reports, suggesting that the way in which the results were averaged is not codicologically optimal.  (The lab had six test results, and by averaging results one can reduce the deviation number which consequently reduces the date range from periods of greater than two centuries to periods of less than two centuries.)  Head has argued that instead of excluding one of the results from the leaves and averaging the remaining five, there should be two averages: one average of all three leaves and one average of the three binding elements.

My estimation following Peter Head’s thesis leaves a radiometric result in the late third through the end of the fourth century.  One should be aware that fourth century manuscripts will typically have calibrated dates ranging back into the third century.  The issues is that the amount of 14C carbon in the atmosphere dipped in the fourth century, and thus fourth century manuscripts generally look like third century manuscripts.  Notably, one of the individual calibrations of the papyri leaves offered a date range into the sixth century!


  1. Christian, thanks for this. I am sure you are going to advance beyond my discussion!! My discussion was simply probing the obvious problems in Kasser's discussion. At that point I knew way too little about carbon 14 dating. Peter M. Head, ‘The Gospel of Judas and the Qarara Codices: Some Preliminary Observations’ Tyndale Bulletin 58.1 (2007), 1-23. On pp. 11-13. See e.g. here: https://www.academia.edu/1175088/The_Gospel_of_Judas_and_the_Qarara_Codices

  2. Church and science should go one track. We are in future and i hope to read more articles such like that.

  3. I couldn't agree more ... I think