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orion-list Radiocarbon

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Dear orioners: for those following the issues with 63 BCE
and the radiocarbon dates I suggest in terms of method that
the 63 BCE terminus hypothesis be evaluated separately
in terms of (a) all non-radiocarbon grounds, and (b)
radiocarbon data alone.  Secondly, as a provisional term the
five radiocarbon dates whose 2-sigma ranges are entirely 
post-63 BCE might be termed "apparent evidence against a 
63 BCE terminus".  The lab-reported dates are actual, not 
apparent, but the conversion of these lab reported dates to
an historical judgment is what is at issue.

Third, for the 5 clearly post-63 BCE AMS dates, there are
basically three possibilities:  (a) the 63 BCE terminus is wrong; 
(b) there is some anomaly in the calibration curve, i.e. a 
regional effect; or (c) contaminated dates.  

After further study and discussions with a radiocarbon scientist, 
I'm convinced now that "b" above is the least likely of the three 
possibilities.  The very possibility of the existence of a true 
"regional offset" itself is not secure.  Apparently, studies from 
the days of atmospheric nuclear testing appear to show
complete air mixing in the northern hemisphere troposphere of 
three months, not 10-20 years; which would mean a true 
regional offset (> 3 months) should not be possible.  There are 
location-dependent offsets measured and reported, but just 
why these occur is subject to different possible explanations, 
e.g. lab offsets or ecosystem factors.  In any case offsets of 
this nature apply to the radiocarbon measurement numbers 
themselves rather than to calendar years.  All of this supports
what Tim Jull said earlier concerning regional offset being a
minor or insignificant factor.

It may therefore in the end be that there are only two, rather 
than three, real possiblities: either the 63 BCE terminus
is wrong, or the five post-63 BCE AMS dates have been 
inaccurately dated.  Here I may owe Tom Simms an apology.  
He kept talking about sample contamination and I assured 
him the problem was likely minimal, at some unknown low 
level of incidence but not likely to be a major factor.  Some 
research underway, to be reported when completed, suggests 
that the potential problem with scrolls AMS dates from 
inadequate sample pretreatment methods may be worse than 
thought.  (The good news is the problems, once identified, are
amenable to solutions.)  It is again as Tim Jull said: the only 
way to find out is to do more measurements and find out.  I do 
not control the timing of the upcoming battery, but it appears 
likely that a third battery of AMS dates may be accomplished 
within the next 3-5 months.

As a final comment on the five "problem" AMS dates for the
63 BCE terminus theory: on the assumption that the AMS dates
are accurate and the palaeographic datings used in the Qumran
field are also accurate, it would be expected that all five of the 
post-63 BCE 2-sigma dates should be "Herodian" hands.  But if
the five "problem" dates are representing problems in the 
radiocarbon measurements (or if the palaeographic dating
assumptions are invalid) a random mixture of "Herodian" and 
non-"Herodian" scribal hands would be predicted.  In fact the 
second pattern, and not the first, is what we see.  Of the five 
dates, three are texts with "Herodian" hands, and two are 
"Hasmonean" hands.  These two are:

   4Q266 D(a): 2sigma (95% confidence): 44 BCE-129 CE 
                     1sigma (68% confidence): 4-82 CE
   4Q521 MessApoc: 2sigma (95% conf.): 49 BCE-116 CE 
                     1sigma (68% conf.): 39 BCE-66 CE

These two texts have published palaeographic "datings" of 
pre-50 BCE and c. 100-80 BCE, respectively.  

Therefore while if any of the five "problem" dates are securely 
corroborated and verified this will essentially be fatal to a 
63 BCE terminus, and if one of them (4QpPsA) is verified 
that will provide the first evidence for 1st century CE Qumran 
text scribal activity, at the same time if two other of the five 
dates (4Q266, 4Q521) are corroborated and verified this should 
also eviscerate confidence in the high-precision palaeographic 
dating system currently in common use.  More is at stake 
than just the 63 BCE terminus in this.  In any case, these 
uncertainties will not be forever.  Radiocarbon is going to 
go one way or the other on these questions.

Greg Doudna
For private reply, e-mail to Greg Doudna <gd@teol.ku.dk>
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