The riddle of the sun stones

When you think about it, it's unsurprising that our ancestors invented "the gods" as an explanation for anything they didn't understand.

They were constantly bombarded by stuff that was outside of the science of their time.  Diseases caused by the unseen action of either genes or microorganisms.  Weather patterns, driven by forces that even in the twenty-first century we are only beginning to understand deeply, and which controlled the all-important supply of food and water.  Earthquakes and volcanoes, whose root cause only began to come clear sixty years ago.

Back then, everything must have seemed as mysterious as it was precarious.  For most of our history, we've been at the mercy of forces we didn't understand and couldn't control, where they were one bad harvest or failed rainy season or sudden plague from dying en masse.

No wonder they attributed it all to gods and sub-gods -- and devils and demons and witches and evil spirits.

As much as we raise an eyebrow at the superstition and seeming credulity of the ancients, it's important to recognize that they were no less intelligent, on average, than we are.  They were trying to make sense of their world with the information they had at the time, just like we do.  That we have a greater knowledge base to draw upon -- and most importantly, the scientific method as a protocol -- is why we've been more successful.  But honestly, it's no wonder that they landed on supernatural, unscientific explanations; the natural and scientific ones were out of their reach.

The reason this comes up is a recent discovery that lies at the intersection of archaeology and geology, which (as regular readers of Skeptophilia know) are two enduring fascinations for me.  Researchers excavating sites at Vasagård and Rispebjerg, on the island of Bornholm, Denmark, have uncovered hundreds of flat stone disks with intricate patterns of engraving, dating from something on the order of five thousand years ago.  Because many of the disks have designs of circles with branching radial rays extending outward, they've been nicknamed "sun stones."  Why, in around 2,900 B.C.E., people were suddenly motivated to create, and then bury, hundreds of these stones, has been a mystery.

Until now.

[Image credit: John Lee, Nationalmuseet, Copenhagen, Denmark]

Data from Greenland ice cores has shown a sudden spike in sulfates and in dust and ash from right around the time the sun stones were buried -- both hallmarks of a massive volcanic eruption.  The location of the volcano has yet to be determined, but what is clear is that it would have had an enormous effect on the climate.  "It was a major eruption of a great magnitude, comparable to the well-documented eruption of Alaska’s Okmok volcano in 43 B.C.E. that cooled the climate by about seven degrees Celsius," said study lead author Rune Iversen, of the Saxo Institute at the University of Copenhagen.  "The climate event must have been devastating for them."

The idea that the volcanic eruption in 2,900 B.C.E. altered the climate worldwide got a substantial boost with the analysis of tree rings from wood in Europe and North America.  Right around the time of the sulfate spike in the Greenland ice cores, there's a series of narrow tree rings -- indicative of short growing seasons and cool temperatures.  Wherever this eruption took place, it wrought havoc with the weather, with all of the results that has on human survival.

While the connection between the eruption and the sun stones is an inference, it certainly has some sense to it.  How else would you expect a pre-technological culture to respond to a sudden, seemingly inexplicable dimming of the sun, cooler summers and bitter winters with resultant probable crop failures, and even the onset of wildly fiery sunrises and sunsets?  It bears keeping in mind that our own usual fallback of "there must be a scientific explanation even if I don't know what it is" is a relatively recent development. 

So while burying engraved rocks might seem like a strange response to a climatic change, it is understandable that the ancients looked to a supernatural solution for what must have been a mystifying natural disaster.  And we're perhaps not so very much further along, ourselves, given the way a substantial fraction of people in the United States are responding to climate change even though the models have been predicting this for decades, and the evidence is right in front of our faces.  We still have plenty of areas we don't understand, and are saddled with unavoidable cognitive biases even if we do our best to fight them.  As the eminent science historian James Burke put it, in his brilliant and provocative essay "Worlds Without End":

Science produces a cosmogony as a general structure to explain the major questions of existence.  So do the Edda and Gilgamesh epics, and the belief in Creation and the garden of Eden.  Myths provide structures which give cause-and effect reasons for the existence of phenomena.  So does science.  Rituals use secret languages known only to the initiates who have passed ritual tests and who follow the strictest rules of procedure which are essential if the magic is to work.  Science operates in the same way.  Myths confer stability and certainty because they explain why things happen or fail to happen, as does science.  The aim of the myth is to explain existence, to provide a means of control over nature, and to give to us all comfort and a sense of place in the apparent chaos of the universe.  This is precisely the aim of science.

Science, therefore for all the reasons above, is not what it appears to be.  It is not objectively impartial, since every observation it makes of nature is impregnated with theory.  Nature is so complex, and sometimes so seemingly random, that it can only be approached with a systematic tool that presupposes certain facts about it.  Without such a pattern it would be impossible to find an answer to questions even as simple as "What am I looking at?"

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The worst century in history

I've always loved a mystery, and for that reason, the European "Dark Ages" have fascinated me for as long as I can recall.

But the moniker itself is off-puttingly self-congratulatory, isn't it?  It's not like Roman rule was that pleasant for your average slob to live under, after all.  Be that as it may, after the conquests of the Roman Empire started to fall apart in the fourth century C.E. from a combination of invasion, misrule, and downright lunacy, things went seriously downhill.  Life was pretty rough until the eighth and ninth centuries, when some measure of order returned as damn near all of Europe coalesced around the Roman Catholic Church, ushering in the Middle Ages.  And what we know about the period in between is... not a hell of a lot.  Accounts are scattered, vague, and full of conflation with mythology and legend.  The few that were written by contemporaries, rather than long after the fact -- such as Gregory of Tours's History of the Franks -- contain as much hagiography as they do history.

St. Gregory and King Chilperic I, from Grandes Chroniques de France de Charles V (fourteenth century) [Image is in the Public Domain]

Which is why I was thrilled to read a paper that appeared in Antiquity about a study of the "worst decade to be alive" -- 536-546 C. E.

The research, which combines the skimpy evidence we have from accounts written at the time with hard scientific data from analysis of ice cores, paints a grim picture.  Writings from the year 536 describe a mysterious "fog" that lasted for eighteen months, generating widespread crop failure and what one Irish cleric called "three years without bread."  From the ice core analysis, medieval historian Michael McCormick and glaciologist Paul Mayewski identified what they believe to be the culprit: a cataclysmic volcanic eruption in Iceland that dropped the global temperature an average of two degrees Celsius in a matter of months.

This was followed by another eruption in 540, and the following year, the single worst plague on record -- the so-called "Plague of Justinian," which killed between a third and a half of the inhabitants of the Eastern Roman Empire, and resulted in so many corpses that people loaded them on ships and dumped them in the Mediterranean.  The disease responsible isn't known for certain, but is believed to be Yersinia pestis -- the same bacterium that caused the Black Death, almost exactly eight hundred years later.  But to give you an idea of the scale, there's reason to believe the Plague of Justinian dwarfed both the fourteenth century Black Death and the Spanish Flu of 1918-1919 -- usually the two examples that come to mind when people think of devastating pandemics.  The death toll is estimated at sixty million.

There probably was a connection between the cold and the plague, too, although not the obvious one that famine triggers disease susceptibility.  Many scholars think that the lack of food, and cold temperatures following a period that had generally been warm, forced mice and rats into homes and on board ships -- not only in close proximity to humans, but in their means of travel.  The fleas they carried, which are vectors for the plague, went with them, and the disease decimated Europe and beyond.

The effects of the eruption, however, were felt all over the Earth.  Tree ring analysis from North America shows 540 and the years following to have been unusually cold, with short-to-nonexistent growing seasons.  Volcanic dust is found in those layers of ice cores everywhere they exist.  Famines occurred in Asia and Central America.

All in all, a crappy time to be around.

Things didn't rebound for almost a hundred years.  Archaeologist Christopher Loveluck, of the University of Nottingham, found traces of dust containing significant amounts of lead in ice strata from the year 640, which he believes were due to a resurgence in silver smelting for coinage.  (I suppose if there's a hundred years during which your three main occupations are (1) not starving, (2) not freezing, and (3) not dying of a horrible disease, then making silver coins is kind of not on your radar.)  And the tree rings and ice cores bear out his contention that this indicates better conditions; although there were a couple of other volcanic eruptions we can see in the glacial records, none were as big as the one in 536.  The silver smelting, Loveluck says, "... shows the rise of the merchant class for the first time."  Things, finally, were improving.

What's coolest about this study -- despite its gruesome subject -- is how hard science is being brought to bear on understanding of history.  We no longer have to throw our hands up in despair if we're interested in a time period from which there were few written records.  The Earth has recorded its own history in the trees and the glaciers, there for us to read -- in this case, telling us the tale of the worst century the human race has ever lived through.

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History by proxy

In a new study from Proceedings of the National Academy of Sciences, we learn something simultaneously fascinating and a little alarming; humanity's fingerprint on the globe is so clear that it can even track our wars, famines, and plagues -- back twenty-five centuries or more.

The whole thing was done using proxy records, which involve using indirect sources of evidence about the past to infer what conditions were like.  A commonly-used one is using the constituents of air bubbles in amber and ice to make inferences about the global average air temperature at the time -- a technique that shows good agreement with the measurements of the same variable using other methods.

Here, in a team effort from the Desert Research Institute, the University of Oxford, the Norwegian Institute for Air Research, the University of Copenhagen, the University of Rochester, and the Alfred Wegener Institute for Polar and Marine Research, researchers studied ice cores from thirteen different locations in the polar northern hemisphere, and found that the levels of one contaminant in the ice -- lead -- was enough to parallel all of the major plagues and wars that occurred in Europe and northern Asia back to 800 B.C. E.

What they found is that lead concentrations in the ice rose when things were quiet and prosperous, probably due to an expansion of smelting operations for items like lead seams for stained-glass windows and impurities in silver ore processing.  The signature of wars was clear, but the signature from plagues was blatantly obvious; the years following the Plague of Justinian (541-542 C.E.) and the two spikes of the Black Death (1349-1352 and 1620-1666 C.E.) were two of the lowest points on the graph.

"Sustained increases in lead pollution during the Early and High Middle Ages (about 800 to 1300 CE), for example, indicate widespread economic growth, particularly in central Europe as new mining areas were discovered in places like the German Harz and Erzgebirge Mountains," said study lead author Joseph McConnell of the Desert Research Institute.  "Lead pollution in the ice core records declined during the Late Middle Ages and Early Modern Period (about 1300 and 1680 C.E.) when plague devastated those regions, however, indicating that economic activity stalled."

Silver smelting plant in Katowice, Poland, ca. 1910 [Image is in the Public Domain]

The authors write:

Lead pollution in Arctic ice reflects midlatitude emissions from ancient lead–silver mining and smelting.  The few reported measurements have been extrapolated to infer the performance of ancient economies, including comparisons of economic productivity and growth during the Roman Republican and Imperial periods.  These studies were based on sparse sampling and inaccurate dating, limiting understanding of trends and specific linkages.  Here we show, using a precisely dated record of estimated lead emissions between 1100 BCE and 800 CE derived from subannually resolved measurements in Greenland ice and detailed atmospheric transport modeling, that annual European lead emissions closely varied with historical events, including imperial expansion, wars, and major plagues.  Emissions rose coeval with Phoenician expansion, accelerated during expanded Carthaginian and Roman mining primarily in the Iberian Peninsula, and reached a maximum under the Roman Empire.  Emissions fluctuated synchronously with wars and political instability particularly during the Roman Republic, and plunged coincident with two major plagues in the second and third centuries, remaining low for >500 years.  Bullion in silver coinage declined in parallel, reflecting the importance of lead–silver mining in ancient economies.  Our results indicate sustained economic growth during the first two centuries of the Roman Empire, terminated by the second-century Antonine plague.

Of course, there's nowhere in the ice cores that has as high a level of lead contamination as recently-deposited ice does.  "We found an overall 250 to 300-fold increase in Arctic lead pollution from the start of the Middle Ages in 500 CE to 1970s," said Nathan Chellman, a doctoral student at the Desert Research Institute, and co-author on the study.  "Since the passage of pollution abatement policies, including the 1970 Clean Air Act in the United States, lead pollution in Arctic ice has declined more than 80 percent.  Still, lead levels are about 60 times higher today than they were at the beginning of the Middle Ages."

As an aside, the Trump administration has steadily rolled back regulations requiring industry to conform to reasonable pollution standards, including allowable levels of air pollution.  So look for the contaminants in ice -- and in your lungs -- to spiral upward once again.

But hey, it means the economy's good, so nothing to worry about, right?

Of course right.

So as I've pointed out (repeatedly), what we are doing does have a measurable, quantifiable effect on the environment, and studies like McConnell et al. should be a significant wake-up call.  And as I've also pointed out, it probably won't.  It's all too easy for people to say, "Meh, what do I care about a little lead in Arctic ice?  So it bothers a few seals and polar bears.  Too bad for them."  And continue with our throw-away, gas-guzzling, conspicuous-consumption lifestyles.

It's cold comfort knowing that when the aliens come here in a thousand years to find out why the Earth is barren, they'll be able to figure it out by looking at the traces we left behind in the ice, soils, rocks, and air.

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This week's Skeptophilia book recommendation is pure fun for anyone who (like me) appreciates both plants and an occasional nice cocktail -- The Drunken Botanist by Amy Stewart.  Most of the things we drink (both alcohol-containing and not) come from plants, and Stewart takes a look at some of the plants that have provided us with bar staples -- from the obvious, like grapes (wine), barley (beer), and agave (tequila), to the obscure, like gentian (angostura bitters) and hyssop (Bénédictine).

It's not a scientific tome, more a bit of light reading for anyone who wants to know more about what they're imbibing.  So learn a little about what's behind the bar -- and along the way, a little history and botany as well.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

The worst century in history

I've always loved a mystery, and for that reason, the European "Dark Ages" have fascinated me for as long as I can recall.

But the moniker itself is off-puttingly self-congratulatory, isn't it?  It's not like Roman rule was that pleasant for your average slob to live under, after all.  Be that as it may, after the conquests of the Roman Empire started to fall apart in the 4th century C.E. from a combination of invasion, misrule, and downright lunacy, things went seriously downhill.  Life was pretty rough until the 8th and 9th centuries, when some measure of order returned as damn near all of Europe coalesced around the Roman Catholic Church, ushering in the Middle Ages.  And what we know about the period in between is... not a hell of a lot.  Accounts are scattered, vague, and full of conflation with mythology and legend.  The few that were written by contemporaries, rather than long after the fact -- such as Gregory of Tours's History of the Franks -- contain as much hagiography as they do history.

St. Gregory and King Chilperic I, from Grandes Chroniques de France de Charles V (14th century) [Image is in the Public Domain]

Which is why I was thrilled to read a paper that appeared last week in Antiquity about a study of the "worst decade to be alive" -- 536-546 C. E.

The research, which combines the skimpy evidence we have from accounts written at the time with hard scientific data from analysis of ice cores, paints a grim picture.  Writings from the year 536 describe a mysterious "fog" that lasted for eighteen months, generating widespread crop failure and what one Irish cleric called "three years without bread."  From the ice core analysis, medieval historian Michael McCormick and glaciologist Paul Mayewski identified what they believe to be the culprit: a cataclysmic volcanic eruption in Iceland that dropped the global temperature an average of two degrees Celsius in a matter of months.

This was followed by another eruption in 540, and the following year, the single worst plague on record -- the so-called "Plague of Justinian," which killed between a third and a half of the inhabitants of the Eastern Roman Empire, and resulted in so many corpses that people loaded them on ships and dumped them in the Mediterranean.  The disease responsible isn't known for certain, but is believed to be Yersinia pestis -- the same bacterium that caused the Black Death, almost exactly eight hundred years later.  But to give you an idea of the scale, there's reason to believe the Plague of Justinian dwarfed both the 14th century Black Death and the Spanish Flu of 1918-1919 -- usually the two examples that come to mind when people think of devastating pandemics.  The death toll is estimated at sixty million.

There probably was a connection between the cold and the plague, too, although not the obvious one that famine triggers disease susceptibility.  Many scholars think that the lack of food, and cold temperatures following a period that had generally been warm, forced mice and rats into homes and on board ships -- not only in close proximity to humans, but in their means of travel.  The fleas they carried, which are vectors for the plague, went with them, and the disease decimated Europe and beyond.

The effects of the eruption, however, were felt all over the Earth.  Tree ring analysis from North America shows 540 and the years following to have been unusually cold, with short-to-nonexistent growing seasons.  Volcanic dust is found in those layers of ice cores everywhere they exist.  Famines occurred in Asia and Central America.

All in all, a crappy time to be around.

Things didn't rebound for almost a hundred years.  Archaeologist Christopher Loveluck, of the University of Nottingham, found traces of dust containing significant amounts of lead in ice strata from the year 640, which he believes were due to a resurgence in silver smelting for coinage.  (I suppose if there's a hundred years during which your three main occupations are (1) not starving, (2) not freezing, and (3) not dying of a horrible disease, then making silver coins is kind of not on your radar.)  And the tree rings and ice cores bear out his contention that this indicates better conditions; although there were a couple of other volcanic eruptions we can see in the glacial records, none were as big as the one in 536.  The silver smelting, Loveluck says, "... shows the rise of the merchant class for the first time."  Things, finally, were improving.

What's coolest about this study -- despite its gruesome subject -- is how hard science is being brought to bear on understanding of history.  We no longer have to throw our hands up in despair if we're interested in a time period from which there were few written records.  The Earth has recorded its own history in the trees and the glaciers, there for us to read -- in this case, telling us the tale of the worst century the human race has ever lived through.

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This week's Skeptophilia book recommendation is a fun one -- Mary Roach's Spook.  Roach is combines humor with serious scientific investigation, and has looked into such subjects as sex (Bonk), death (Stiff), war (Grunt), and food (Gulp).  (She's also fond of hilarious one-word titles.)

In Spook, Roach looks at claims of the afterlife, and her investigation takes her from a reincarnation research facility in India to a University of Virginia study on near-death experiences to a British school for mediums.  Along the way she considers the evidence for and against -- and her ponderings make for absolutely delightful reading.