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Re: orion-list Radiocarbon

On Fri, 27 Aug 1999 17:39:00 +0200, gd@teol.ku.dk writes:
>Yesterday I cited, in the strongest form I could, the case from
>radiocarbon against a 63 BCE terminus hypothesis.  At first blush 
>it sounds immediately decisive, indeed virtually airtight: five 
>separate radiocarbon dates, of 19 total Qumran texts dated, 
>give two-sigma ranges entirely later than 63 BCE, at 95% 
>confidence reported by the lab for each one of these datings.  
>The reason I do not consider these 5 dates a falsification of a 63 BCE 
>terminus hypothesis is simply this: in four of those five cases, the 
>edge of the two-sigma range is so close to 63 BCE that it appears 
>hairsplitting to claim certainty, in the absence of further data and 
>context.  E.g. 1QH (47 BCE...), 4Q266 (44 BCE...), 4Q258 #2 
>(50 BCE...), 4Q521 (49 BCE...).  In only one case is the start of the 
>2s range unambiguously and clearly removed from 63 BCE in terms 
>of calendar years: 4QpPsA (3 CE...).  

   Ah, now that's more like it.

>Readers of orion might consider: (a) if you had no radiocarbon data,
>would you know a 63 BCE terminus hypothesis was excluded on 
>some other grounds?  Can you articulate what those grounds are,
>and how secure they are?  And (b) as an analogy and as a mental
>exercise, consider the following calibrated radiocarbon dates for three 
>texts and answer this hypothetical question: "Does the radiocarbon 
>data below falsify an hypothesis that all of these texts were deposited 
>no later than 134 CE?"  (Please take time to think this through, and 
>form your personal answer, before continuing further.  Note especially
>the two sigma range of the second item below.)  
>	1sigma (68% confidence)	2sigma (95% confidence) 
>	132-324 CE			80-389 CE
>	237-340 CE			140-390 CE
>	131-240 CE			84-322 CE
>In fact this is not hypothetical.  These are the radiocarbon dates on 
>three Bar Kochba-era texts of known dates, none later than 134 CE, 
>that were measured by the same lab and in the same battery that 
>produced four of the five apparent post-63 BCE radiocarbon dates 
>on Qumran texts, i.e. at Tucson.  This example should serve as a 
>caution against overinterpretation of the existing data.  It should be 
>a caution against premature certainty or inappropriate claims of 
>what is "probable" and "improbable".  The edges of reported 2s 
>calibration ranges should be regarded as just a little bit fuzzy.  

   Well, they certainly confirm the items are from the Bar Kochba 
   Revolt since that's where they were found.  It doesn't show 
   that they DON'T, for sure.

>The second issue is of course the all-important issue of contam-
>ination.  The important points are: (a) there is, distressingly, an 
>almost certain occasional incidence of contaminated datings among
>the first two batteries; (b) the actual incidence, while probably not 
>high, is unknown, particularly in the Tucson battery (in the smaller 
>Zurich battery there are grounds to suppose the incidence may be
>c. 10%); (c) all other things being equal, cases of contaminated 
>dates tend to show up at the edges of the total distribution rather 
>than in the middle of the cluster.

   Wait a minute - are you speaking of DSS text fragments?

>In the Tucson battery some 18 Dead Sea texts were dated.  I 
>identify at least three cases of suspected contamination among 
>these: (1) 4Q258 (1st sample), likely.  (2) 4Q345, an economic text 
>from Seiyal/Hever, because it gave an unusual 371-171 BCE date
>among otherwise Herodian and post-Herodian economic texts.  
>And (3) 4QpPsA, because it disagrees with 1QpHab, which I think 
>almost must be contemporary.  Please appreciate and believe me 
>when I say this analysis of the 4QpPsA/pHab discrepancy is what 
>I would think no less strongly even if I believed in a 68 BCE deposit 
>date.  I realize many do not share this same intuition of a pPs/pHab 
>contemporaneity, but to me, it is very strong.  The reason for focusing 
>on pPs rather than pHab as the suspected problem between the two 
>is of course pPs's outlier appearance relative to the total distribution, 
>whereas pHab is in the midst of the distribution.
   Again, you address nothing of the handling treatment by the
   recovery teams and the analysis people.  I've heard of some
   cavalier treatment.

>Perhaps many or most may agree with me that at least one of the 
>above looks contaminated, maybe two, and some may even go with 
>me on the suspected third.  In none of these cases do we have any 
>secure knowledge of whether those dates are or are not contaminated--
>we're groping in the dark.  And we don't know the true incidence 
>throughout the Tucson battery as a whole.  If 2 or 3 of the ones I have 
>just cited were contaminated, the true incidence could be a little higher, 
>perhaps even another 2 or 3.  Not necessarily--but it just is not known.
>For these reasons the 5 apparently secure post-63 BCE dates are
>not secure, in my view, in establishing that any text at Qumran is 
>certainly later than 63 BCE.  Four of the five dates are only a few 
>years away in the start of their 2sigma from 63 BCE, which risks
>interpreting the data overprecisely to claim 63 BCE is certainly 
>excluded.  The fifth, 4QpPsA, is, by coincidence (and it is 
>coincidence), on my personal short list of suspected contaminated 

   There are no secure records of fragment handlings, are there?

>This is why I do not regard existing radiocarbon data as definitively 
>inconsistent with a 63 BCE terminus hypothesis, but instead as 
>ambiguous.  I do not regard the issue as one of rejection of data, 
>but rather what is appropriate to claim as knowledge on the basis
>of existing data.  What light future data will shed on the existing 
>data of course remains to be seen.  
>Greg Doudna

   If you had better prospects of getting data clear of contamination
   would you be more hopeful?

Tom Simms   
For private reply, e-mail to Tom Simms <tsimms@mailserv.nbnet.nb.ca>
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