[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

orion-list Radiocarbon

    [The following text is in the "iso-8859-1" character set]
    [Your display is set for the "ISO-8859-8" character set]
    [Some characters may be displayed incorrectly]

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...).  

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.  

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.

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.

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 

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

For private reply, e-mail to Greg Doudna <gd@teol.ku.dk>
To unsubscribe from Orion, e-mail to majordomo@panda.mscc.huji.ac.il with
the message: "unsubscribe Orion." For more information on the Orion Center
or for Orion archives, visit our web site http://orion.mscc.huji.ac.il.