From: BRITISH ARCHAEOLOGY, Journal of the Council for British
Archaeology, December 1997
text translation service for 25 worldwide languages
Cometary impact is gaining ground as an explanation
of the collapse of civilisations, writes Benny Peiser.
At some time around 2300 BC, give or take a century or two, a large number of the major civilisations of the world collapsed, simultaneously it seems. The Akkadian Empire in Mesopotamia, the Old Kingdom in Egypt, the Early Bronze Age civilisation in Israel,
Anatolia and Greece, as well as the Indus Valley civilisation in India, the Hilmand civilisation in Afghanistan and the Hongshan Culture in China – the first urban civilisations in the world – all
fell into ruin at more or less the same time. Why?
A thousand years later, at around 1200 BC, many of the civilisations of the same regions again collapsed at about the same time. This time, disaster overtook the Myceneans of Greece, the Hittites of Anatolia, the Egyptian New Kingdom, Late Bronze Age Israel, and the Shang Dynasty of China.
The reasons for these widespread and apparently simultaneous disasters – which coincided also with changes of cultures and societies elsewhere, such as in Britain – have long been a fascinating mystery. Traditional explanations include warfare, famine, and more recently ‘system collapse’, but the apparent absence of direct archaeological or written evidence for causes, as opposed to the effects, has led many archaeologists and historians into a resigned assumption that no definite explanation can possibly be found.
Some decades ago, the hunt for clues passed largely into the hands of natural scientists. Concentrating on the earlier set of Bronze Age collapses, researchers began to find a range of evidence that suggested that natural causes rather than human actions, may have been initially responsible. There began to be talk of climate change, volcanic activity, and earthquakes – and some of this material has now found its way into standard historical accounts of the period.
Agreement, however, there has never been. Some researchers favoured one type of natural cause, others favoured another, and the problem remained that no single explanation appeared to account for all the evidence.
Over the past 15 years or so, however, a new type of ‘natural disaster’ has been much discussed and is beginning to be regarded, by many scholars, as the most probable single explanation for widespread and simultaneous cultural collapse, but not only in the Bronze Age but at another times as well. The new theory has been advanced largely by astronomers, and remains almost completely unknown amongst archaeologists (a few notable exceptions include the dendrochronologist Prof Mike Baillie of Queen’s University, Belfast, and Dr Euan MacKie at Glasgow University). The new idea is that these massive cultural disasters were caused by the impact of comets or other types of cosmic debris on the Earth.
The hunt for natural causes for these human disasters began when the Frenchman Claude Schaeffer, one of the leading archaeologists of his time, published his book ‘Stratigraphie Comparee et Chronologie L’Asie
Occidentale’ in 1948. Schaeffer analysed and compared the destruction layers of more than 40 archaeological sites in the Near and Middle East, from Troy to Tepe Hissar on the Caspian Sea and from the Levant to Mesopotamia. He was the first scholar to detect that all had been totally destroyed several
times in the Early, Middle and Late Bronze Age, apparently simultaneously.
Since the damage was far too excessive and did not show signs of military or human involvement, he argued that repeated earthquakes might have been
responsible for these events. At the time he published, Schaeffer was not taken seriously by the
world of archaeology. Since then, however, natural scientists have found widespread and unambiguous evidence for abrupt climate change, sudden sea level changes, catastrophic inundations, widespread
seismic activity and evidence for massive volcanic activity at several periods since the last Ice Age, but particularly at around 2200BC, give or take 200 years.
Areas such as the Sahara, or around the Dead Sea, were once farmed but became deserts. Tree rings show disastrous growth conditions at c 2350BC, while sediment cores from lakes and rivers in Europe and Africa show a catastrophic drop in water levels at this time. In Mesopotamia, vast areas of land appear
to have been devastated, inundated, or totally burned.
Scholars who, following Schaeffer, favour earthquakes as the principal cause of civilisation collapse argue that the world can expect vast earthquakes every 1000 – 2000 years, leading to widespread abandonment of sites; while scholars who prefer climate change as the principal cause argue that severe droughts caused agriculture to fail and that societies inexorably fell apart as a result.
Yet what was the cause of these earthquakes, eruptions, tidal waves, fire-blasts
and climate changes? By the late 1970s, British astronomers Victor Clube and
Bill Napier of Oxford University had begun to investigate cometary impact as
the ultimate cause. Then in 1980, the Nobel prizewinning physicist Luis Alvarez
and his colleagues published their famous paper in ‘Science’ that argued that
a cosmic impact had led to the extinction of the dinosaurs. He showed that large
amounts of the element iridium present in geological layers dating from about
65 million BC had a cosmic origin.
Alvarez’s paper had immense influence and stimulated further research by such British astronomers as Clube and Napier, Prof Mark Bailey of
the Armagh Observatory, Duncan Steel of Spaceguard Australia, and Britain’s best known astronomer Sir Fred Hoyle. All now support the
theory of cometary impact and loosely form what is now known as the British School of Coherent Catastrophism.
These scholars envisage trains of cometary debris which repeatedly encounter the Earth. We know that tiny particles of cosmic material penetrate the atmosphere every day, but their impact is insignificant.
Occasionally, however, cosmic debris measuring between one and several hundred metres in diametre strike the Earth and these can have catastrophic
effects on our ecological system, through multimegaton explosions of fireballs which destroy natural and cultural features on the surface of the
Earth by means of tidal-wave floods (if the debris lands in the sea), fire blasts and seismic damage.
Depending on their physical properties, asteroids or comets that punctuate the atmosphere can either strike the Earth’s surface and leave an impact crater, such as the well-known Barringer Crater in Arizona caused by an asteroid made of iron some 50,000 years ago. At least ten impact craters around the world dating from after the last Ice Age, and no fewer than seven of these date from around the 3rd
millennium BC – the date of the widespread Early Bronze Age collapses – although none occurred in the Near East.
Alternatively, comets and asteroids can explode in the air. A recent example – known as the Tunguska Event – occurred in 1908 over Siberia, when a bolide made of stone exploded about 5km above ground and completely devastated an area of some 2,000 km’ through fireball blasts. The cosmic body, although thought to have measured only 60 m across, had an impact energy of about 20 to 40 megaton, up to three times as great as the Arizona example (about 15 megaton), and was equivalent to the explosion of about 2,000 Hiroshima-size nuclear bombs – even though there was no actual physical impact on the Earth. (The object that destroyed the dinosaurs, by
contrast, is thought to have had a diametre of about 10km.) A smaller cometary blast occurred over the Brazilian rainforest in 1930.
In addition to the physical impact of comets, the British astronomers point to occasional massive influx of cosmic dust high above the stratosphere which can cause a dramatic drop of global temperature,
leading to the suspension of agriculture; and also the massive influx of cosmic chemicals (associated with dust) with, as yet, incalculable biochemical potentials but which may be harmful to DNA and can trigger
Until recently, the astronomical mainstream was highly critical of Clube and Napier’s giant comet hypothesis. However, the crash of comet Shoemaker-Levy 9 on Jupiter in 1994 has led to a change in attitudes. The
comet, watched by the world’s observatories, was seen split into 20 pieces and slam into different parts of the planet over a period of several days. A
similar impact on Earth would have been devastating.
According to current knowledge, Tunguska-like impacts occur every 100 years or so. It is, therefore, not farfetched to hypothesise that a super-Tunguska may occur every 2000, 3000 or 5000 years and would be capable of triggering ecological crises on a continental or even global scale. In the past, skeptics have demanded the evidence of a crater before they would accept an argument of cosmic impact, but it
is now become understood that no crater is necessary for disastrous consequences to ensue. The difficulty this leaves scholarship, however, is
that in a Tunguska Event no direct evidence is left behind. It may be impossible to prove that one ever took place in the distant past.
The extent to which past cometary impacts were responsible for civilisation collapse, cultural change, even the development of religion, must remain a hypothesis. But in view of the astronomical,
geological and archaeological evidence, this ‘giant comet’ hypothesis should no longer be dismissed by archaeologists out of hand.
Dr Benny J Peiser is a historian and anthropologist at Liverpool John Moores University
PROCEEDINGS OF THE SECOND S.I.S. CAMBRIDGE CONFERENCE NOW AVAILABLE:
BRITISH ARCHAEOLOGICAL REPORTS-S728, 1998
“Natural Catastrophes During Bronze Age Civilisations:
Archaeological, geological, astronomical and cultural perspectives.”
Edited by Benny J. Peiser, Trevor Palmer and Mark E. Bailey.
ISBN 0 86054 916 X., 252 pp., 39 photos, 46 figures,13 tables.
£36.00. [Archaeopress, Oxford]