Ghost cities

I just finished reading The Long Summer: How Climate Changed Civilization by Brian M. Fagan, and what struck me over and over again was an astonished thought of how we managed to survive at all.

For most of human history (and prehistory), the human species lived in communities of various sizes that were constantly teetering on the brink of mass starvation.  Fagan makes the point again and again; for the majority of humanity, all it took was one bad season to spell complete disaster.  There was no Plan B.  Except for the small number of civilizations that lived in areas with sufficient wild foods to forage, a drought or a flood or a freeze at the wrong time and you were in deep, deep trouble.

Size and power were no guarantors of safety.  The Mycenaeans, the Indus Valley Civilization, the Mayan Empire, the Pueblo Culture, the Tiwanaku People, and the Sumerians all declined and collapsed at least in part due to the vagaries of the climate.  More recently, the Little Ice Age contributed to the Great Famine of 1315-1317 which affected most of Europe and killed millions; and repeated crop failures during the eighteenth century, coupled with the monarchy's seeming inability to deal with them, almost certainly were part of what gave momentum to the French Revolution.

Despite all this, our intrepid ancestors not only survived, but in many places, thrived.  Sometimes even in regions where it's hard to imagine.  For example, consider two archaeological discoveries of hitherto-unknown cities -- one in the desert of northwestern Arabia, and the other in the Amazonian lowlands of Ecuador.

A study led by Guillaume Charloux of the Centre National de la Recherche Scientifique found the remains of a fortified complex surrounding the Khaybar Oasis dating to the fourth and third millennium B.C.E., giving evidence of a permanent settlement that persisted for at least several centuries.

The authors write:

The multidisciplinary investigation carried out between 2020 and 2023 by the Khaybar Longue Durée Archaeological Project (CNRS-RCU-AFALULA) demonstrates that the Khaybar Oasis was entirely enclosed by a rampart in pre-Islamic times, like several other large regional walled oases in north-western Arabia (Tayma, Qurayyah, Hait, etc.).  The cross-referencing of survey and remote sensing data, architectural examinations and the dating of stratified contexts have revealed a rampart initially some 14.5 km long, generally between 1.70 m and 2.40 m thick, reinforced by 180 bastions.  Preserved today over just under half of the original route (41 %, 5.9 km and 74 bastions), this rampart dates back to the Bronze Age, between 2250 and 1950 BCE, and had never been detected before due to the profound reworking of the local desert landscape over time.  This crucial discovery confirms the rise of a walled oasis complex in northern Arabia during the Bronze Age, a trend that proved to be central to the creation of indigenous social and political complexity.

A different study that also came out this week looked at the ruins of a city complex with buildings, gardens, streets, and plazas, now buried in the tangle of the Ecuadorian rain forest near the Upano River.  This one is even more mysterious than the Arabian settlement; we knew there were people living in northwestern Arabia back then, even if we didn't know they had built a city.  Here, archaeologists have found the remains of a complex, settled civilization, its beginnings contemporaneous with the Roman Republic and which lasted for a thousand years, and we have no idea who the people were that inhabited it -- neither what language they spoke nor how they were related to other Indigenous groups in the area before and afterward.

[Image licensed under the Creative Commons James Martins, Amazon rainforest - panoramio, CC BY 3.0]

Sacha Vignieri, writing for Science, commented about the research:

When intact, the Amazonian forest is dense and difficult to penetrate, both on foot and with scanning technologies.  Over the past several years, however, improved light detection and ranging scans have begun to penetrate the forest canopy, revealing previously unknown evidence of past Amazonian cultures.  Rostain et al. describe evidence of such an agrarian Amazonian culture that began more than 2000 years ago.  They describe more than 6000 earthen platforms distributed in a geometic pattern connected by roads and intertwined with agricultural landscapes and river drainages in the Upano Valley.  Previous efforts have described mounds and large monuments in Amazonia, but the complexity and extent of this development far surpasses these previous sites.

Of course, the fact that both the Arabian and the Amazonian cities were ultimately abandoned indicates that they too fell prey to the capriciousness that characterizes much of human history.  Whether the cause was war, famine, drought, disease, or some combination -- all too often those come together -- the Khaybar Oasis and Upano Valley civilizations left their intricately-constructed towns, either dispersing into other communities or else dwindling and finally dying.

Whichever it was, all we have are the ghostly remains of cities once inhabited by thriving populations -- a stark reminder of our own tenuous grasp on survival, something we often forget about because of the hubris of modern society.  I'm reminded of Percy Bysshe Shelley's haunting and poignant poem "Ozymandias," which seems a fitting place to end:

I met a traveller from an antique land,
Who said—Two vast and trunkless legs of stone
Stand in the desert.  Near them, on the sand,
Half sunk a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them, and the heart that fed;
And on the pedestal, these words appear:
"My name is Ozymandias, King of Kings;
Look on my Works, ye Mighty, and despair!"
Nothing beside remains.  Round the decay
Of that colossal wreck, boundless and bare
The lone and level sands stretch far away.

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The mystery from Manu

So much of the damage we've done to the planet hasn't been deliberate destructiveness; it's been due to our carelessly stomping about the place.  We've long had the attitude that resources will never run out, that we can get away with doing whatever we want with no consequences, that nature will rebound like it always does.  There's little awareness of the absolute fragility of it all.

The "bull in a china shop" metaphor seems all too apt.

Of course, that mindset does require a good dollop of willful ignorance.  Just two weeks ago, the United States Fish and Wildlife Service declared that 22 species in the US that were previously classified as critically endangered are now officially considered extinct.  The most famous of them is the Ivory-billed Woodpecker, the largest woodpecker species native to North America, victim to habitat loss as the wetland forests where it lived were drained, the trees felled for lumber.  A full nine of the 22 are bird species endemic to Hawaii, eight of them part of the unique group called Hawaiian honeycreepers that were decimated by the double whammy of habitat loss and susceptibility to avian malaria, carried by the introduced Asian tiger mosquito.

So to think "everything's just fine" you have to make a practice of not paying attention.

One of the problems is that in some of the most vulnerable places in the world, species are disappearing before they're even identified and studied.  Take, for example, the species of tree native to the Amazon basin of Peru that was first seen by scientists in 1973 -- and that has just now been classified and named.

Robin Foster of the Smithsonian Tropical Research Institute was the one who noticed it, while walking in Manu National Park -- and despite a thorough knowledge of Amazonian flora, he couldn't figure out what it was.  "When I first saw this little tree, while out on a forest trail leading from the field station, it was the fruit -- looking like an orange-colored Chinese lantern and juicy when ripe with several seeds -- that caught my attention," Foster said.  "I didn't really think it was special, except for the fact that it had characteristics of plants in several different plant families, and didn't fall neatly into any family.  Usually I can tell the family by a quick glance, but damned if I could place this one."

So Foster sent a branch of the plant to the Field Museum of Chicago, where it sat in the herbarium for almost fifty years.  When DNA analysis became de rigueur for doing taxonomy, back in the 1990s, researchers tried extracting DNA from the dried leaves -- unsuccessfully.  Then last year, scientist Patricia Álvarez-Loayza, who is part of the team that studies the ecosystem in Manu National Park, found a living specimen of the tree, and this time the DNA extraction worked.

Aenigmanu alvareziae

The results were a shock to botanists, because it showed beyond any question that the little tree belonged to an obscure tropical family called Picramniaceae, made up of 48 (now 49) species native to northern South America, Central America, and the Caribbean, but not common anywhere.  "When my colleague Rick Ree sequenced it and told me what family it belonged to, I told him the sample must have been contaminated.  I was like, no way, I just couldn't believe it," said Nancy Hensold of the Field Museum, part of the team that studied the plant and finally identified its affinities.  "Looking closer at the structure of the tiny little flowers I realized, oh, it really has some similarities, but given its overall characters, nobody would have put it in that family." 

The plant was christened Aenigmanu alvareziae -- the genus name means "mystery from Manu," while the species name honors Patricia Álvarez-Loayza, who found the living specimen that helped to place the species.

What strikes me about this whole story is how easily the branch of this little tree could have been forgotten in the herbarium, or the plant itself overlooked completely.  The Amazon is a big place, large swaths of which are unexplored.  While one odd plant species may not seem all that important, this does give us a sense of the extent to which we're blundering around damaging living ecosystems without even understanding them fully.  "Plants are understudied in general," said Robin Foster, the first scientist who noticed Aenigmanu back in 1973.  "Especially tropical forest plants.  Especially Amazon plants.  And especially plants in the upper Amazon.  To understand the changes taking place in the tropics, to protect what remains, and to restore areas that have been wiped out, plants are the foundation for everything that lives there and the most important to study.  Giving them unique names is the best way to organize information about them and call attention to them.  A single rare species may not by itself be important to an ecosystem, but collectively they tell us what is going on out there."

Conservation isn't some kind of academic game, and rare species shouldn't just be of interest to the taxonomists.  We need to understand on a visceral level that you can't pull threads out of the tapestry of life without the entire thing coming unraveled.  Chief Seattle said it best, back in 1854: "The Earth does not belong to man; man belongs to the Earth.  This we know.  All things are connected like the blood which unites one family...  Whatever befalls the Earth befalls the sons of the Earth.  Man did not weave the web of life; he is merely a strand in it.  Whatever he does to the web, he does to himself."

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During the first three centuries C.E., something remarkable happened; Rome went from a superpower, controlling much of Europe, the Middle East, and North Africa, to being a pair of weak, unstable fragments -- the Western and Eastern Roman Empires --torn by strife and internal squabbles, beset by invasions, with leaders for whom assassination was the most likely way to die.  (The year 238 C.E. is called "the year of six emperors" -- four were killed by their own guards, one hanged himself to avoid the same fate, and one died in battle.)

How could something like this happen?  The standard answer has usually been "the barbarians," groups such as the Goths, Vandals, Franks, Alans, and Huns who whittled away at the territory until there wasn't much left.  They played a role, there is no doubt of that; the Goths under their powerful leader Alaric actually sacked the city of Rome itself in the year 410.  But like with most historical events, the true answer is more complex -- and far more interesting.  In How Rome Fell, historian Adrian Goldsworthy shows how a variety of factors, including a succession of weak leaders, the growing power of the Roman army, and repeated epidemics took a nation that was thriving under emperors like Vespasian and Hadrian, finally descending into the chaos of the Dark Ages.  

If you're a student of early history, you should read Goldsworthy's book.  It's fascinating -- and sobering -- to see how hard it is to maintain order in a society, and how easy it is to lose it.

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