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[22]Adventure & Experience | [23]History
The Maya's ingenious secret to survival
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(Image credit: Michael Godek/Getty Images)
Mayan ruins at Tikal National Park, Guatemala
By Alex Fox
9th August 2021
Tikal was the economic and ceremonial hub of the Maya civilisation. But
its stone palaces and temples would never have been constructed without
mastery over one vital substance.
S

Standing in the ancient Mayan city of Tikal in Guatemala, visitors are
surrounded by steep limestone pyramids nearly as tall as Notre Dame
cathedral while the calls of howler monkeys and toucans emanate from
the site's rainforest backdrop. Constructed without the aid of beasts
of burden, metal tools or the wheel, these grandiose stoneworks served
as the seats of power for the kings and priests who ruled over what was
one of the most influential city states in the Maya realm, which
spanned Mexico's Yucatan Peninsula, Guatemala, Belize as well as
portions of Honduras and El Salvador.

Tikal was an economic and ceremonial hub of a civilisation that, in
light of [26]recent laser-based aerial surveys that revealed more than
60,000 structures hidden for centuries by thick jungle, may have once
encompassed as many as 10 to 15 million people in total.

In the presence of Tikal's massive stone palaces and temples, each one
oriented to attend to the sun's daily transit across the sky, the
Maya's prowess as architects and astronomers looms large. But the Maya
never would have accurately predicted eclipses and these monuments
never would have risen up towards the sky without the mastery of
something much more elemental to Mayan survival at Tikal: water.

With no rivers or lakes nearby, the Maya had to create a network of
huge reservoirs at Tikal to collect and store enough rainwater during
the region's prodigious wet season to last its sizable population –
estimates range from [27]40,000 to as many as [28]240,000 people at the
city's 8th Century peak – through the four- to six-month dry season.
These reservoirs facilitated more than 1,000 years of Mayan presence at
Tikal, from roughly 600 BC until the site's urban core was finally
abandoned by the ruling class around 900 AD.

Last year, archaeologists using modern scientific techniques
[29]revealed a new depth to the Maya's hydrological feats. Sediment
cores taken from Tikal's reservoirs show that the Maya created the
oldest known water filtration system in the western hemisphere.
The Maya left behind an astonishing amount of architecture and artwork
(Credit: Samantha Haebich/Getty Images)

The Maya left behind an astonishing amount of architecture and artwork
(Credit: Samantha Haebich/Getty Images)

The Maya's water purification system was so advanced that one of its
key materials, zeolite, is still widely used in water filters today.
Zeolites are a type of volcanic mineral made mostly of aluminium,
silicon and oxygen that forms when volcanic ash reacts with alkaline
groundwater. They come in many forms and have unique physical and
chemical properties that allow them to [30]filter out contaminants
ranging from heavy metals to tiny microbes. Individual zeolite grains
have a porous, cage-like structure, which makes them excellent physical
filters, and they are also negatively charged, which means other
elements will readily bind to them. This means that when water passes
through zeolites, suspended particles can get physically or chemically
stuck to the grains of zeolite while the water keeps flowing through
the gaps.

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Though archaeologists only found zeolites in one of Tikal's reservoirs,
now referred to as Corriental, shards of clay vessels found there
suggest the purified waters of Corriental were used specifically for
drinking.

The researchers behind this discovery say the Mayan use of zeolite is
the oldest known use of the mineral for water purification in the
world, predating its next appearance in a sand filtration system
developed by British scientist [34]Robert Bacon in 1627 by roughly
1,800 years. The Maya's zeolite-powered water filtration system, which
scholars say looks to have first been constructed around 164 BC, is
predated by a cloth filter known as the Hippocratic sleeve that was
developed in ancient Greece around 500 BC, but the Maya's method would
have been far more effective at removing invisible contaminants such as
bacteria or lead.

"I'm Native American and I've always been bothered that archaeologists
and anthropologists have traditionally assumed that the Indigenous
people of the Americas did not develop the technological muscle that
was found elsewhere in the ancient world in places like Greece, Egypt,
India or China," said Kenneth Tankersley, an archaeological geologist
at the University of Cincinnati and lead author of [35]the study
documenting the Maya's use of zeolite. "This system provided the Maya
with safe drinking water for more than 1,000 years and other filtration
systems known from that era were primitive by comparison – the early
Greek filtration method was just bags of cloth."

I've always been bothered that archaeologists and anthropologists have
traditionally assumed that the Indigenous people of the Americas did not
develop the technological muscle that was found elsewhere in the ancient
world

Tikal is located in what is now northern Guatemala, and in this part of
the world there are only two seasons: very wet and very dry. To make
matters even more challenging, the wet season's torrential downpours
swiftly drain away because, as rainwater seeps through the thin
topsoil, it becomes acidic enough to dissolve the calcium-rich
limestone that makes up the region's bedrock. This creates what
geologists call a karst landscape riddled with sinkholes and caves
where the water table is roughly [36]200m below the surface, well out
of the Maya's reach.

Without bodies of freshwater nearby to draw from, residents of this
Central American metropolis had to devise ways of making water last
when it arrived in the wet season. That's where the reservoirs came in
– and because Tikal is centred around a hillock, the Maya were able to
artfully utilise the slopes to funnel water into those reservoirs. Even
the great central plaza, which sits between Temples One and Two and is
flanked by the main acropolis, is paved with huge stones that were all
placed at just the right incline to drain water into canals that
emptied into the nearby Temple and Palace reservoirs.
The Maya relied on seasonal rainfall for their water supply, which they
collected in reservoirs (Credit: Stuart Birch/Getty Images)

The Maya relied on seasonal rainfall for their water supply, which they
collected in reservoirs (Credit: Stuart Birch/Getty Images)

Modern visitors to Tikal will need to make an extra effort to locate
the reservoirs, which live on today mostly as depressions in the soil,
but some of the dams and earthen berms used to impound the vast
quantities of water that once slaked the city's thirst are still
evident to the informed observer. The Palace reservoir is estimated to
have once stored [37]31 million litres of water, and the
zeolite-purified [38]Corriental is thought to have had a
58-million-litre capacity in its heyday.

The discovery of Corriental's filtration system emerged from fieldwork
conducted around 2010, when researchers collected 10 core samples of
sediment from four of Tikal's reservoirs. These cores revealed that
dangerous levels of [39]contamination from the heavy metal mercury and
the tell-tale signs of toxic algal blooms plagued the Palace and Temple
reservoirs near Tikal's core around the time the ruling elites
abandoned the city centree in the 9th Century.

But almost as striking as the contamination itself was the fact that
the Corriental reservoir stayed virtually pristine even as the Palace
and Temple reservoirs grew toxic. When Tankersley looked more closely
at the Corriental samples, he found four discrete layers of sand that
featured bits of crystalline quartz and zeolites that didn't appear in
any of the other reservoirs.

When the team surveyed the surrounding area there were no natural
sources of this type of sand, let alone zeolites, leading the
researchers to suggest the material had been intentionally brought in
for use in some kind of filter at the entrance to the reservoir.

By chance, one of the researchers on the project knew of a depression
some 30km northeast of Tikal featuring similar-looking sand that is
known as Bajo de Azúcar, which locals had told him has crystal-clear,
sweet-tasting water. Testing revealed that Bajo de Azúcar's rocks and
sand did contain zeolites and thus could have been Tikal's source for
the zeolites at Corriental.
Home to as many as 240,000 people at its 8th Century peak, the site was
abandoned around 900 AD (Credit: Hvalar/Getty Images)

Home to as many as 240,000 people at its 8th Century peak, the site was
abandoned around 900 AD (Credit: Hvalar/Getty Images)

"Without a time machine we don' know what happened exactly," said
Tankersley, "but it doesn' take a lot of deduction to imagine someone
from Tikal thinking: 'If sweet, clean water is coming out of this
crystalline volcanic tuff, maybe we could break some off and use it to
make our water clean as well.'"

The Maya may not have understood what the zeolite in particular was doing,
but they understood the importance of keeping water clean

The researchers hypothesise that the zeolite sand might have been
sandwiched between layers of woven plant leaves called petates to make
filters. Those filters might have then been embedded in porous walls of
limestone bricks that the Maya installed in the path of the water
flowing into the reservoir. According to the study detailing the Maya's
use of zeolite, sand by itself would have made the water look clear,
but wouldn't have had any impact on microbes or mercury. With the
addition of zeolite, the Maya got clear water that was also clean even
by modern standards.

"The Maya may not have understood what the zeolite in particular was
doing, but they understood the importance of keeping water clean," said
Lisa Lucero, an anthropologist at the University of Illinois who was
not involved in the paper, "and they employed their technology and
their knowledge of the environment to purify their drinking water."

The four layers of zeolite-containing sand suggest that the filter was
blasted out by flood waters during particularly violent rainy seasons
and subsequently rebuilt several times over.

Though Corriental is the only place that this Mayan zeolite filtration
system has been found, that doesn't rule out its use elsewhere. Liwy
Grazioso, director of Guatemala's Miraflores Museum and co-author of
[40]the study that discovered the contamination of the Palace and
Temple reservoirs, says she hopes this finding will encourage more
study of Mayan reservoirs.
Lidar technology has revealed many more temples, pyramids and causeways
hidden in the rainforest (Credit: Matt Champlin/Getty Images)

Lidar technology has revealed many more temples, pyramids and causeways
hidden in the rainforest (Credit: Matt Champlin/Getty Images)

"I don't think Tikal was the only place with this technology," said
Grazioso. "Reservoirs were everywhere in the Maya world and only a
handful have been studied, but if we don't study them, we'll never
know."

For Tankersley, these discoveries showcase the riches that can be found
when researchers look beyond shiny material artefactse made of gold or
jade.

He suggests that visitors to Tikal should not just marvel at the
structures, but also contemplate the people who built them 1,000 or
even 2,000 years ago without machines or pack animals. "Think about
what their accomplishments were," he said, "and remember that this is
not an extinct people, those accomplishments are the heritage of
Central America's modern Indigenous population."

[41]Ancient Engineering Marvels is a BBC Travel series that takes
inspiration from unique architectural ideas or ingenious constructions
built by past civilisations and cultures across the planet.

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