Did Asteroids And Comets Turn The Tides Of Civilization?

The heart of humanity seems at times to have lost its cadence, the rhythmic beat of history collapsing into impotent chaos. Wars raged. Pestilence spread. Famine reigned. Death came early and hard. Dynasties died, and civilization flickered.

Such a time came in the sixth century A.D. The Dark Ages settled heavily over Europe. Rome had been beaten back from its empire. Art and science stagnated. Even the sun turned its back. "We marvel to see no shadows of our bodies at noon, to feel the mighty vigor of the sun's heat wasted into feebleness," Italian historian Flavius Cassiodorus wrote at the time. "We have summer without heat. The crops have been chilled by north winds, (and) the rain is denied."

In China, "the stars were lost from view for three months." The sun dimmed, the rain failed, and snow fell in the summertime. Famine spread, and the emperor abandoned his capital amid political and economic disasters.

Then came pestilence. The Justinian plague, named for a Byzantine emperor, apparently began in central Asia, spread into Egypt, and then swept across Europe. Hundreds of thousands died.

The world had gone to hell in a hurry, if the historical accounts can be believed. But with neither evidence of global disaster nor a viable cause, the records were widely doubted by historians.

New evidence, however, supports the tales of ancient scribes and identifies brief but brutal times of worldwide ecological catastrophe. The evidence is in tree rings, which clearly show several years of cold weather that stunted growth beginning in A.D. 536 and especially after A.D. 540-541. The rings show similar events that began in 1628 B.C. and 1159 B.C., and rare written documents of those times seem also to describe cataclysmic social collapse.

What weapon does nature wield that is powerful enough to alter the course of civilizations within a few years? The most likely explanation, the best fit with the evidence, is that described by both Chinese and Europeans as dragons in the sky: Pieces of comets (or perhaps of asteroids) crashed into Earth, spewing a veil of dust that encircled the world and dimmed the sun.

A much larger and rarer bolide (an exploding meteoric fireball) is assumed to have ended the reign of the dinosaurs some 65 million years ago. A smaller and more common one exploded over the Tunguska River in the Siberian wilderness 91 years ago with 2,000 times the power of the bomb that devastated Hiroshima in 1945. And just five years ago, astronomers watched the fragmented comet Shoemaker-Levy 9 plow spectacularly into Jupiter.

I believe the association between the tree-ring data and historical documents and folktales is real: Earth faced catastrophic environmental dislocation at or around 1628 B.C., 1159 B.C., and A.D. 540 (and probably in 2354 B.C. and 208 B.C., as well) because of near-miss comets, either through dust-loading of the atmosphere as Earth passed through the comet's dusty tail or through direct bombardment by cometary fragments. (They must have been near misses, because if we had been hit by a full-blown comet in the past 10,000 years or so, we wouldn't be here today.) This hypothesis is not proven, but the circumstantial evidence is overwhelming.

The strongest evidence comes from tree rings and the science of dendrochronology. Tree rings record the age of a tree, with a distinct ring of growth produced each year. The width of each ring depends on growing conditions, so each year's growth in a particular area leaves a unique signature (a reflection of fat, moderate, or lean growing conditions) in the tree-ring record.

By calibrating the rings through progressively older trees from a specific region, archaeologists can build millennia-long chronologies that allow them to date ancient wooden artifacts. (See Discovering Archaeology, May/June, page 45.) The pattern of tree rings in an artifact can be matched to the regional chronology to determine the year in which the tree died.

A less-well-known consequence of these chronologies is that we can now identify periods in which trees grew very little or not at all. This is indicated by clusters of extremely narrow rings, which suggest extremely cold growing seasons. A band of these narrow rings occurred after A.D. 540 and lasted about six years in parts of Europe, Asia, and North America.

Similar ring patterns are found around 1159 B.C. and 1628 B.C. These dates may coincide with the collapse of Bronze Age civilizations across Eurasia. They may also be recalled in the biblical book of Exodus and contemporary records from China.

The first inkling that tree rings might record catastrophic events came in the mid-1980s from dendrochronologist Val LaMarche and volcanologist Kathy Hirschboeck. In the extremely long-lived bristlecone pines of the western United States, they noted a frost-damage ring at 1627 B.C. and suggested it might reflect the massive eruption of the Santorini volcano in the Aegean Sea. Similar frost rings followed the eruptions of Krakatoa in Indonesia (1883) and Katmai in Alaska (1912).

After a major volcanic eruption, Earth is veiled by a layer of fine debris circulating in the stratosphere. This layer reflects sunlight away from Earth, causing the surface to cool.

As a result of their suggestion, I searched the ring patterns derived from oak logs that had been preserved in the peat bogs of Ireland. I found that many trees exhibited the worst growth - the narrowest rings - of their lifetimes starting in 1628 B.C. Only a few other such events were seen in the rings, but two others were at 1159 B.C. and A.D. 540. Those years are close to dates for acid-rich layers (attributed to volcanic eruptions) that had been identified in ice cores taken in Greenland. We seemed to be onto something.

Then astronomer Kevin Pang of the California Institute of Technology (Caltech) noted that 1628 B.C. and 1159 B.C. roughly mark the beginning and end of the Shang Dynasty of Bronze Age China. Both ends of the dynasty featured, according to ancient Chinese texts, environmental disasters - dimming of the sun and summer frosts that caused crop failures and famine. Pang notes also the Chinese concept of "mandate of heaven," wherein a dynasty reigned only as long as it protected the well-being of its people. This notion might have originated in the coincidence of dynastic change and climatic disaster.

The Caltech team also noted similar descriptions from A.D. 536-545 that describe climatic disruptions that led to catastrophic famines and great loss of life.

Much was going on in the world around these three dates. The four centuries of the Greek Dark Ages, which began after the Mycenaean era of mainland Greece collapsed amid great social upheaval, are thought to have begun in the twelfth century B.C. This period also saw the end of the once-mighty Hittite civilization of Anatolia in the Near East and of Bronze Age Israel.

The situation in Egypt is more ambiguous. Egypt's prosperous New Kingdom grew out of a century or so of warfare and upheaval known as the Second Intermediate Period, which itself followed the end of the Middle Kingdom. The New Kingdom has been dated from 1550 B.C. to 1070 B.C. While that is 70 years later than our two dates (1628 B.C. and 1159 B.C.), the time span is almost exactly the same. Some scholars have questioned traditional Egyptian dating, and it seems possible the timing of the New Kingdom, some 3,500 years ago, might be a little off.

Then the volcano hypothesis began to dim. Volcanologists noted that volcanoes normally would not be powerful enough to collapse dynasties - the dust and acid, even if sufficient to dim sunlight, washes out of the atmosphere within a few years. And a review of the ice-core evidence from Greenland failed completely to confirm an exceptional volcanic eruption at A.D. 540.

It appears now that something far more damaging than volcanoes may have been at work here, especially after seeing unassailable proof that comets can hit planets: the extraordinary spectacle of comet Shoemaker-Levy 9 crashing into Jupiter in 1994. Comets appear in Chinese records of events at the beginning and end of the Shang dynasty. Were the catastrophic environmental downturns at 1628 B.C., 1159 B.C., and A.D. 540 caused by encounters with comets?

Archaeologists and astrophysicists do not necessarily read each other's work, and it mostly escaped notice that three British cometary astrophysicists - Mark Bailey, Victor Clube, and Bill Napier - had published a highly relevant paper in 1990. They wrote that Earth had been at increased risk of bombardment by cometary debris in the period A.D. 400-600. They based their conclusion on the increased number of great meteor showers during that period.

It's hard to overestimate the devastation that could result from a serious bolide impact on Earth. The impact of fragments measuring between one and several hundred meters across can cause fiery, multimegaton explosions that destroy natural and cultural features across huge areas through fire blasts, earthquakes, and tidal waves (if the debris arrives over the sea).

The danger in A.D. 400-600, concluded Bailey and colleagues, was of Earth running into a "cosmic swarm" of objects the size of the one that exploded over Tunguska, Siberia, in 1908. Some astronomers believe we can expect Tunguska-type impacts every 50 years on average, while an impact with explosive power in the 1,000- to 10,000-megaton range - a super Tunguska event - is likely in any 5,000-year period. Such impacts could trigger enormous global ecological catastrophe.

Impacts between those two extremes might be expected often enough to account for these calamities. Direct evidence, however, is scanty. Associating craters to specific events is problematic at best; the Tunguska event left no significant crater at all, since the bolide exploded a few kilometers above the surface. Impacts in or over the ocean would not leave physical evidence.

We turned, then, to the written record and oral traditions. Comets were extraordinary objects that seemed rarely to escape written notice. Zachariah of Mitylene noted about A.D. 540 that - a great and terrible comet appeared in the sky at evening time for 100 days." Chinese texts about the same time say: "Dragons fought in the pond of the K'uh o. They went westward. ... In the places they passed, all the trees were broken." Similar descriptions are common throughout the Old World.

Sixth-century events generally are well-dated. But with more ancient documents and traditions, dating usually is ambivalent at best. This is why similarly spaced events in the second millennium B.C. are so interesting. What are the chances of similarly spaced events in both Hebrew and Chinese histories, both with cometary associations, arising by chance?

There is, I feel, a strong case for the contention that we do not inhabit a benign planet. This planet is bombarded relatively often. If this story is correct, we have been bombarded at least three times - and probably five times - since the birth of civilization some 5,000 years ago. And each time, the world was changed.

MIKE BAILLIE is a leading dendrochronologist and Professor of Palaeoecology at Queen's University, Belfast, Northern Ireland. His book, Exodus to Arthur, describes in detail his theory of comet encounters and turning points of civilization.

Anna is not proof of the high literacy rate (read Vassiliev's history if you want more on that) but the fact that classical educations persisted into the 11th century. There was no "Dark Age" in the Empire--classical antiquity survived in Christianized form until the Muslims destroyed the Empire. The Dark Age in the East begins in the 1300's when the Empire is reduced to a city-state and the barbarous Turks are in control: literacy drops so that the stereotypes of 'illiterate Greeks' become a reality just as illiterate Franks were a reality in the West during the "Dark Ages."

I haven't a clue who JasonC is, save that he shows up on the ping list with me.

As for arrogance, I think the whole scholarly tradition in Western Europe and America which follows Gibbon in disparaging the Christian Empire, a civilization which spanned over 1000 years and was the dominant power in Europe and the Levant through much of it, is the height of arrogance in its cultural self-centeredness.

Great original thoughts which do not accord with fact are called fantasies and are the province of adolecents, not adults.

>Great original thoughts which do not accord with fact are called fantasies

Tell that to H. Schlieman before he discovered Troy, and a bookfull of others who went beyond "accepted facts". Only pedantic dullards are trapped in the fantasy that accepted "facts" are the only "facts", or are, in fact, facts at all.

The problem with the idea is not going beyond "accepted facts" but proceeding on the basis of false "facts". The Dark Ages were a local phenomenon. It is particularly ironic that the post mentions Justinian: during the so called Dark Ages, Justinian gave the definitive codification of Roman Law, classical learning still alive, and science was no more stagnant than during the pagan Imperial period. Indeed it was during this period that the liquid fire which burned on contact with water, so called "Greek fire" was discovered.

The arts were not stagnant: Imperial secular art still exhibitted full knowledge of perspective, used in the conventional way, while Orthodox iconography, far from forgetting the laws of perspective, deliberately turned them upside down, so that the viewer became the vanishing point, and what was beyond the icon became visually as well as symbolically the view into a larger 'spiritual space'.

Gee, some others seem to expect reasons why. Which is why I gave sch reasons I was asked for comments, you know. It is not like they were unsolicited. If you only want comments that think your latest idea is the greatest thing since sliced bread, why not just say so in the ping?

Why would I "try again", when nobody has addressed a single one of my previous points on the substance? You think it is more arrogant of me to give reasons, than to dismiss mine with a wave of your stylistic tone wand without any? At any rate, it settles nothing in rational argument, whereas reasons given for a view, and not addressed by the other side in a debate, have a certain heft to them.

I have been busy so have missed some of your pings!

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About that celestial spanking..."This planet is bombarded
relatively often. If this story is correct, we have been bombarded at least three times - and probably five times -
since the birth of civilization some 5,000 years ago. And each time, the world was changed."

If this story is correct, we have been bombarded at least three times - and probably five times - since the birth of civilization some 5,000 years ago. And each time, the world was changed."

Think it'll hit the UN building? Maybe the Hague?

"I say in a billion years descendants of the cockroaches will be running this place."

Not likely. They've remained virtually unchanged for hundreds of millions of years. I'd put your money on the small rodents, they have a good track record in that regard.

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