I found an interesting article, and a most interesting line..
"circa 2200 BC (now 2350 BC)
(2) THIRD MILLENNIUM BC CLIMATE CHANGE & OLD WORLD COLLAPSE
From: JOURNAL OF ARCHAEOLOGICAL SCIENCE 25,2 (1998), pp. 185-86
Book Review
By Mike Baillie m.baillie@qub.ac.uk
Third Millennium BC Climate Change and Old World Collapse.
Dalfes, H.N., Kukla, G. and Weiss, H. (Eds) 1996
Springer-Verlag (Published in cooperation with NATO
Scientific Affairs Division), Berlin, Heidelberg, New York, Barcelona,
Budapest, Hong Kong, London, Milan, Paris, Santa Clara, Singapore,
Tokyo
ISBN 3-540-61892-9
xiv, 728 pages, 156 figures, 35 tables
price DM 398,-; öS 2905.40; sFr 347,-; £ 172.-
This volume represents a brave attempt to bring together the evidence
for an environmental event in the later third millennium BC.
Thirty-three papers attempt to assemble the evidence from various
natural records and from archaeology. Their success is inevitably
constrained by the one key factor critical in any such endeavour -
chronological resolution. Thus, as a preliminary to the review I feel
it is necessary to set the scene from a chronological standpoint.
The problem posed by Dalfes, Kukla and Weiss is an inherently
interesting one. At the time the papers were assembled Weiss and
Courty were of the opinion that somewhere around 2200 BC there had
been a truly catastrophic environmental event. There was also a lot of
evidence pointing to the centuries between, say, 2300 BC and 1900 BC
representing some sort of environmental downturn, with widely altered
precipitation patterns. So a major question could be couched as
follows.. Were the widespread effects in Asia, Africa and Eastern
Europe actually the result of a general decline over some centuries,
or were they the result of an initial catastrophic trigger event with
longer-term implications? This is a general problem in studies of the
past where dating resolution is poor and where it is impossible to
relate different strands of evidence in real time. It is well typified
by the "suck in and smear" effects suggested in Baillie (1991). These
contrary effects represent a serious impediment to understanding past
phenomena. Abrupt or "point" events tend to be smeared by radiocarbon
dating. Thus radiocarbon effectively conceals abrupt events. The
converse case is where precisely-dated events, e.g. abrupt
environmental downturns deduced from tree-rings, tend to "suck in"
proximate but poorly dated evidence. In such cases it is easy to
envisage the creation of false horizons.
The present volume could be viewed as an exposition on exactly these
concepts. However, it is also important to know that new evidence,
deduced since the volume was produced, has actually made these points
even more emphatically. It is known that an abrupt downturn in Irish
oaks at 2354-2345 BC (Baillie 1995) falls close to the Icelandic Hekla
4 tephra horizon dated to 2310+/-20 CalBC by the wiggle-matching of
high precision radiocarbon dates (Hall et al. 1994). Courty (1997) has
now revised the dating of the original c.2200 BC abrupt environmental
event seen at Tell Leilan, in Syria, to c.2350 BC! Thus this volume of
papers has now to be seen against the existence of what may well be a
very dramatic and widespread environmental downturn - a classic point
event - the nature of which is hinted at by the report of both tephra
and glass spherules at and around the destruction layer at Tell
Leilan.
Do the contributing authors succeed in convincing the reader of the
existence, and chronology, of the proposed environmental change(s)?
The contributions (and I will mention only a few) start with Hassan
covering the breakdown known as the First Intermediate Period in
Egypt, given as 2180-2134 BC, though these cannot be true calendrical
dates. Hassan discusses the issue of the Nile floods in the context of
lake levels in Africa and suffers immediately the problem of
attempting to handle traditional historical dates in Egypt and
radiocarbon chronologies in Africa. Elsewhere Butzer quantifies the
difficulties by pointing out that at Lake Turkana, even with 15
radiocarbon determinations the dating of an abrupt rise in level
around 2150-2050 BC has "a relatively course resolution of +/-100
years". Butzer questions the very idea of a global event and sees no
good evidence for an abrupt change to "greater aridity affecting the
Near East" between 2400-1900 BC.
These few lines nicely exemplify the difficulties. Are we looking at,
or for, an event starting at 2400 or 2350 or 2200 or 2180 BC? Butzer
with his "2400-1900 BCE" has broadened the debate to a full half
millennium - a time period so long that we could reasonably expect
some environmental changes to be recorded in most areas. Courty and
Weiss remind us that there are possibly related socio-economic
disturbances from Egypt, Palestine, the Indus and the Aegean, but of
course there is no good evidence to link these possibly-related
collapses chronologically. Virtually the same applies in the Aegean
handled by Manning. While traditionally there is an Aegean wave of
collapse around 2200 BC, the dating is poor. The Early Helladic II
civilization collapses just when it seems to be at its peak, but what
date is the collapse? Is it c.2350 BC, or c.2200 BC? Manning points
to a related episode of severe soil erosion, unfortunately dated by a
single radiocarbon determination, which calibrates to 2900-2350 CalBC,
but ends up concluding that whatever the date of the EHII collapse the
date of the start of the succeeding EHIII is "after c.2300-2200 BC
(again with no precision)".
Really this is the joy of the whole book. Whether looking at evidence
from the Indus collapse, from drought in Bohemia, from pollen
sequences in Turkey or the Near East or Italy or from varves in
Germany, just about everyone thinks they can see evidence for
environmental change somewhere in the late third millennium BCE.
No-one can specify whether its initiation is really abrupt, nor when
that initiation was. Courty and Weiss have set a series of hares
running with their apparently abrupt and catastrophic event at c2200
BC (now c2350 BC). Can anyone else catch up? Students can be set
endless projects to mine this book in search of the answer.
I cannot resist drawing attention to Harvey Weiss's concluding
remarks. Given their evidence for what appears to be a "blast from the
sky" at Tell Leilan, Weiss is put in the uncomfortable position of
being probably the first archaeologist to have to suggest an impact
from cometary debris in recent millennia. I have absolutely no
problems with that concept but Weiss does; he is torn between claiming
a "hit" and being cautious. He stakes his claim to immortality by
saying
The abrupt climate change at 2200 BC (now 2350 BC),
regardless of an improbable impact explanation,
situates hemispheric social collapse in a global,
but ultimately cosmic, context.
If Baillie (1998) ever sees print, Weiss is going to find strong
circumstantial support that he is probably correct on all counts.
With abrupt change in ancient records, previously obscured by poor
chronological control, more common than previously imagined.
Kukla presents a nice piece on the philosophical difficulty of
disproving events "it is more difficult to prove that something didn't
happen than that it did". This is much in keeping with the suck-in
effect, where loosely dated evidence may be drawn in to support an
event. It then becomes difficult to disprove the event as this would
require better dating of a range of poorly-dated phenomena. This
raises the question whether the act of postulating a significant event
circa 2200 BC (now 2350 BC) has actually created one? I don't
personally think it does. Sufficiently many of the 33 contributions
see evidence for environmental alteration in the later third
millennium BC that something has to have been going on. Their problem
is that in any period of three to four, to five, centuries there is
plenty of time for all sorts of environmental downturns in all sorts
of areas. The real question remains, is there any evidence for a
synchronous global, or even hemispheric, environmental event. Nothing
in the book currently proves that there was. However, the drawing
together of the several contributions provides the student with a mine
of relevant information. The book is a must for the library shelves of
any departments interested in environmental change or in the
archaeology of the third millennium BC or in systems collapse.
The book has typographical errors sprinkled throughout and several
papers clearly required more rigorous proof reading by the editors.
More damning in a volume of this kind is the lack of a consistent
convention on dates. This is particularly significant when the
intention is to see what happened in a tight period of a few centuries
some four millennia ago. Ideally all historical and
dendrochronological dates should have been AD and BC, or BCE. All
historical/archaeological dates older than 600 BC should have been
quoted with estimated errors; this would also apply to dates from
ice-cores and varve sequences. Raw radiocarbon ages should have been
presented as BP with quoted errors, while calibrated radiocarbon ages
should have been signalled as CalAD or CalBC and should have been
quoted with their calibrated 2-sigma ranges. Failure to enforce a
dating code means that the reader has to work hard to compare evidence
both within and between papers. None of these criticisms damage the
work as a whole.
http://abob.libs.uga...c/cc022398.html
Alewyn, on 16 November 2011 - 05:34 AM, said:
