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orion-list Re: more about Radiocarbon

I will try to respond to Greg's and Tom Simm's comments.

Greg Doudna wrote:

> Returning to the topic of radiocarbon dating and the Scrolls,
> there is no way the existing data on the texts, if accurate,
> can be harmonized with a 63 BCE terminus for the scrolls.
> Although I suggested this in a previous post, if it was not
> direct enough I wish to make the point explicit here.  The
> calibration curve between 55 BCE and 85 BCE is essentially
> flat, at about 2075 +/- 20 throughout these three decades.

True, but this is surely a very narrow range from which to try to elucidate any
age information better than +/-20yrs !

> This means any texts from c. 85-63 BCE should all yield
> the same measurement, c. 2075 +/- 20, within margins of
> error.  (Older than 85 BCE the calibration curve rises.)  Any
> texts which measure significantly less than c. 2075 +/- 20
> are therefore indicating younger than 63 BCE.

I checked with the actual data (listed in Stuiver et al., Radiocarbon, vol. 40,
p.1127-1151, 1998) and agree.

> Five texts did measure significantly below 2075 +/- 20.
> These are:
>  1QH                    1979 +/- 32
>  4Q266 D(a)         1954 +/- 38
>  4Q258 S(d)         1823 +/- 24 (#1)/ 1964 +/- 45 (#2)
>  4Q171 pPs(a)      1944 +/- 23
>  4Q521 MessAp   1984 +/- 33
> It can be seen that these numbers are not consistent with the
> calibration curve level at 85-55 BCE.

Tom Simms calculated a mean for these data of 1941+/-31 radiocarbon yrs BP.  By
doing this we assume all these samples date the same "event".  Let us assume for
the moment this is true.
I calculate the following weighted means for these data:

All data:                                                    1962+/-14 yr BP
if we exclude the value of 1823+/-24:        1926+/-28 yr BP

Hence, the 2-sigma range of the 1962+/-14 yr BP average would be from 1934-1990
yr BP.  This would appear based on intercepts with the calibration curves to be
around 5BC-65AD.

We usually calculate these results using a computer program, INTCAL98.  These
results would give the following:

Radiocarbon Age                        Calibrated Age
                                                    1-sigma            2-sigma

1926+/-28                                32-125AD          5-130AD
1962+/-14                                25-67AD            3-78AD
Simms's mean:
1941+/-31                                27-117AD          17-129AD

> These cannot be explained as random scatter.

These data could be explained by random scatter if we assume they all represent
some common event.  However, taken in conjunction with the older ages of the
other DSS samples, they would be discrepant.  The question is why?  This could
be due to contamination, other lab errors, etc., or to the samples actually
being of different age.  If they are all contaminated, why then are they so
consistent ?

> On the hypothesis that many or even most
> of the 19 Qumran texts had true dates in the years 85-55 BCE
> (and none younger) one would expect somewhere between
> only 0 and 1 texts to give numbers like the above--but not five.
> Five of this kind of number is about 4-5 too many.

This is true for this hypothesis...

> (The reason I spoke in earlier discussions on orion in terms
> of possible compatibility between 63 and these dates was
> because of an error in interpretation of the regional offset issue.
> I was using calendar years instead of radiocarbon measurement
> years for the c. +/- 20 location-offset possibility.

As you have already discussed, offsets due to regional effects are very small
+/-20 yr and cannot explain the differences.  In any case, they are all from the
same region.

> The conclusion is: there is no reconciling the above data with 63
> BCE on the assumption that these are accurate measurements.

Quite so.

> But now I wish to address a question to Tim Jull, if he is listening.
> In fact, although many in the Qumran field perceive differently,
> there is no basis to know of post-63 BCE text activity among the
> Qumran texts other than these radiocarbon dates.  There is a
> story that seems plausible to many surrounding 68 CE, but that
> is as strong as the positive case is for post-63 BCE.  It therefore
> becomes critically important to evaluate the meaning of this
> radiocarbon data rightly.
> You have rightly noted that it is improper to reject data points
> without cause.  Yet if I may turn the question around, is it safe
> to believe all unexcluded data points in terms of deep and
> far-reaching historical conclusions?

No, of course not.   We need a sizeable body of data might assist such a

> Here is the problem.
> Among the 19 Qumran texts given AMS datings, 2 of these
> (4QTQahat at Zurich; 4QSd at Tucson) appear to have had
> problems in their datings.  In neither case was the contam-
> ination, if that is what it was, that caused these results
> detectable or visible to either lab under microscope.  If this
> is the case with 2 datings, what is the proper evaluation of
> the remaining 17 in terms of drawing historical conclusions?

You mentioned 5 or 6 which had different ages, not 17.  I think you mean 17 is
the total collection of dates?

> How does one determine the latest date of floruit of an
> archaeological assemblage or floruit or cluster from a battery
> of AMS datings?  (In this case, the latest known Qumran
> text production.)

The best thing would be to have sufficient data to resolve a distribution of
ages and one might be able to determine this from such results.  However, I
should point out (again) that there are some small fluctuations in the
calibration of the time period of interest and this may prevent us resolving
very small age differences.

Thanks, Tim

For private reply, e-mail to "A.J.T. Jull" <ajtjull@physics.arizona.edu>
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