By Eric Vandenbroeck and co-workers

New Model of Urbanization

What happened to the great cities of the Mayans? The prevailing theory is that their civilization and cities were brought down by prolonged drought, or some Malthusian combination of horrors involving overpopulation, climate change, and overexploitation of the land, possibly augmented by disease.

Actually, the Mayans produced two phases of urbanization: the Preclassic of small cities, which collapsed, and the Classic period, when urban hubs with great temples would arise. The apogee was around 700-750 C.E. By around 900, most of the cities had returned to the jungle.

Analyzing the Urbanization Paradox and using Mesoamerica as a model has upended the paradigm of the rise and collapse of the Mayan cities.

The earliest cities were formed by Neolithic farmers who left the land and congregated, but why would they do that? At the level of the individual, why would he suddenly abandon the land, the home, the animals, and the local network and move away? Farmers pay a huge cost for abandoning the security of farm, home, and community only to risk starving on the road, and that is the so-called urbanization paradox.

 

Spears and Butter

Nearly half the planet's population lives in cities: 45 percent of Earth's 8.2 billion people. That's up from 20 percent in 1950. Yet how cities arose in the first place has been a riddle.

There was some surprise in archaeological circles when permanent settlement turned out to predate agriculture. The theory had been that until people could grow food, they had to roam. Yet in some places that could offer food security, the earliest permanent homes outside caves predated farming and the Neolithic revolution by thousands of years.

A reproduction of a mural depicting a pre-Hispanic ceremony of maize brew being served.

Actual cities did, however, only arise after farming: Jericho about 10,000 years ago, Catalhoyuk in Turkey 9,500 years, Eridu in Sumer some 7,500 years ago. At the same time, the Cucuteni-Trypillian culture was coalescing in the form of tremendous settlements in central Europe, though researchers argue whether tens of thousands of people constitute a city if there is no evidence of hierarchy, specialized craftsmanship, or monuments. In China, the earliest cities seem to have appeared around 7,000 years ago.

McCool qualifies that it's difficult to nail down the birth of cities because the classic characteristics don't all emerge at once, and some are causes of urbanization, and some are consequences. The thresholds are arbitrary. So the paper doesn't bog down on what an early city was or wasn't. They care that it was costly for farmers to uproot and ask why they did, and why cities arose where they did.

Their answer boils down to hard times that render the farm unsafe: war, gradual environmental change, or climate shocks in a mixed environment. The farmers abandon the "butter" in the bad and cluster in the good, and if enough food can be produced to sustain an expanding population in the good place, then a village, a town, and then a city may arise.

As of writing, there are 33 megacities, each with more than 10 million people. Indonesia's largest capital, Jakarta, heads the pack with 42 million residents. Of course, some cities are shrinking, the UN adds, among them Mexico City, though how many people live there apparently depends on who you ask.

Panel portraying Mayan royal ceremonies, uncovered in Guatemala.

So, early cities began with fleeing farmers, the authors posit. War is one plausible cause. As people claimed desirable land, they became vulnerable in a new way. When powerful invaders escaping their own troubles came, farmers fled; and where afflicted farmers gathered, they could afford each other protection, but this can only go on for so long.

The more people congregate at a spot, the more depleted the local environment will become, and the more competition over resources will ensue. Ultimately, the environmental destruction will outweigh the added benefit of more people. So once peace descends, the risk of war is replaced by the risk of famine. People will leave the city, which dissolves – unless they learn to scale up food production.

The Mayan pyramid of Calakmul, Mexico.

So conflict can get people to aggregate, but alone, it's unstable. Big cities can grow only in productive areas, and where the people learn to achieve economies of scale in agriculture.

The necessity of achieving economies of scale had not been understood before, he adds.

But this can only go on for so long, too. To advance further and reach megacity status in antiquity, which they did, mere economies of scale won't cut it.

As the population density increases, even the most fertile land will inevitably become exhausted. "You will get to the point where the populations outstrip the food supply. So the people have to intensify production, working harder to produce more food per unit of land. You have to get more technological."

A limestone depiction of captives being presented to the Maya ruler, circa 785.

From the Near East to the forests of South America, the solutions would include fencing in animals, building canals and dams, terracing slopes, and so on. It increases yield, but you have to work a lot harder for that to happen.

Note that the great Mayan cities grew in lowlands, with ample land suitable for cultivation. The Preclassic villages began to coalesce about 3,000 years ago, coalescing where conditions were favorable. Then came "the first Mayan collapse" in the first century. Many of these cities were abandoned, and then the Mayans' fortunes picked up again.

During the Classic period, their populations exploded, especially from the year 500 or so. At its heyday, Tikal housed tens of thousands, according to some scholars, though how many tens of thousands is debatable. Claims range from 40,000 to over 100,000, which has been called a "preposterous" overestimation. Then came the final decline, starting in the eighth century.

The Mayan ruins of Tikal, 500 km north of Guatemala City.

 

Canals From Space

The scale of the decline and collapse is inevitably colored by how large the city populations had been, which is unclear: If there were 100,000, the collapse is tremendous; if there were 1,000, one is less moved. So the gravity of the phenomenon may be unclear but the trend isn't.

"People don't intensify until they have to," McCool adds. We hit population thresholds, then must increase carrying capacity by intensifying production. When farmers start to build agriculture infrastructure, like big reservoirs or large terraces or gigantic canals, the startup costs are enormous – but they unlock the economies of scale.

The economies of scale in agricultural infrastructure mean, the more people work on a project, the more you pool costs and the less the cost per person.

In the conflict model, everybody does worse, but they have to cluster because it's not safe to live outside. But once economy of scale enters the model, the more people arrive, the better each one does. When the threshold is reached again, as it inevitably will be, they can intensify again; build more complex, larger agricultural infrastructure. This can go on for centuries. The Mayan infrastructure, canals, raised fields, and terraces, can be seen from space.

Water reclamation was developed all over the arid Near East, in Israel and Jordan's Black Desert. Here and in South America and Asia, whole mountains were terraced. Massive infrastructure unlocks economies of scale, and people migrate in. But this too can only go on for so long.

One of the first battles in the war between Bonampak and Yaxchilan is elaborately painted at the Maya ruins of Bonampak, 537–583 C.E.

 

Sick of the Gods

Investment projects that unlock economies of scale encourage aggregation so big we think of them as cities, but they also fuel inequality. The first arrivers become the established residents and typically have better claim to land than migrants; they may let in desperate incomers, but not for free – rather, in exchange for rent or labor. The elites can exploit everybody else, and everybody else is not necessarily grateful.

"Circling back to the Classic Mayan collapse, the theory had been that they were destroyed by drought. But the hard data shows the period between 800 and 900 was wet. The agrarian economy of scale was starting to collapse. No more was being constructed, and what they had wasn't being maintained. It seems the land was becoming less productive.

letting ritual; King Itzamnaaj B'alam II is shown holding a torch, while his wife Lady K'ab'al Xook draws a barbed rope through her pierced tongue.

King Itzamnaaj B'alam II, also known as Shield Jaguar II, was a powerful Mayan ruler of the city of Yaxchilán from 681 to 742 AD. He presided over a period of growth for the city and is famously depicted in its art, particularly on Lintel 24, performing a bloodletting ritual with his wife, Lady K'ab'al Xook (Lady Xoc).

A lot of tropical forest was disturbed during the Classic period, the data show – trees were chopped down to grow food. This decreases ecological resilience in the long run. As the environments become denuded and the cities become less productive, the economy of scale weakens. The Maya had afforded their elites a godlike status, so there was certainly inequality and exploitation, the professor adds. We all know how that ends.

Their cities didn't end in drought. The data shows the weather grew wetter. Apparently, the oppressed simply went back to the countryside to farm for themselves and regain their autonomy. Under favorable climate conditions, the benefits of city life no longer outweigh the costs.

And how would this model apply to the Near Eastern condition? When our earliest cities arose, it was the Holocene, and the Sahara and Arabia were wetter. Most arose later, in climatic conditions with which we are more familiar. But this never does seem to have been a peaceful region, so the war aspect of the model applies beautifully, as do the aspects of climate change and shocks, all plausibly leading our early farmers to flee, from flash floods or drought and/or enemies, and congregate for protection in good places, such as a perennial spring or a riverbank, where they would set their stake, establish a right and start to demand rent or labor from the next lot on the run.

 

 

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