Biblical Hebrew Forum

["Greg Doudna" <gdoudna AT earthlink.net>]

Ken, the short answer is the margins of error on individual
radiocarbon dates on Qumran texts are greater than the
claimed precisions of the palaeographic datings, and also
give the appearance, with limited data, of being a bit 
more erratic. Therefore within the Qumran field while there
is interest in radiocarbon dating there is uncertainty as to
whether it is as 'effective as' palaeographic date estimates.
Radiocarbon data, produced by real labs in the real world,
is data that is 'messier'. The palaeographic date estimates
on Qumran texts are all harmonized, smoothly and precisely 
dated to quarter- or half-centuries, with no known means of 
falsification, hence a lot less 'messy'.

It is useful to grasp the distinction between accuracy and 
precision. Precision is the margin of error claimed. Most 
radiocarbon dates on Qumran texts after calibration give
maybe a 100-150 year range at 95% confidence. (These 
margins of error coming from strong labs such as Zurich 
and Tucson accurately represent true margin of error--if the sample
is not affected by contamination.) But palaeographic datings
are routinely published with claims of c. 25-50 year precision.
So the palaeographic date estimates beat the radiocarbon
dates on precision. But precision is not the same thing
as accuracy. It is possible to be precise and inaccurate,
and to have less precision but that lower-precision claim
be a more accurate claim. 
 
There are issues of interpretation as well: if the
narrow paleographic-dating estimates fell anywhere within 
the broader margin of error given by the C14 dating, this has
been commonly interpreted within the Qumran field as
confirmation of the precise paleographic dating (when it 
would be more accurate to say, instead, that the paleographic 
dating was not inconsistent with that C14 date). See
my article in Flint and Vanderkam, DSS after Fifty
Years, vol. I, 1998; also a further discussion on radiocarbon
in my Dec. 1999 Qumran Chronicle monograph, and
finally an article which will be in the next issue of
_Radiocarbon_ journal authored by Rasmussen, van der Plicht,
Cryer, Doudna, Cross, and Strugnell, which presents
research and discussion of issues of sample contamination
and Qumran text radiocarbon dating. 

Greg Doudna

 
> Nobody here has mentioned the dates provided by the 1990 accelerator mass
> spectrometry tests listed by VanderKam (_The Dead Sea Scrolls Today_,
> 17-19). Is this because they are not known, or are they not considered
> relevant, accurate, or sufficiently precise for our purposes?
> 
> Ken Penner
> Ph.D. student, Biblical Field (Early Judaism)
> McMaster University
> Hamilton, Canada
>