Museum of Fine Arts, Boston
Mayan society often used cinnabar, a deep red pigment that got its hue from mercury sulfide.
The civilization took full advantage of the technology of the ancient Mayans. But everything has its limits.
A trio of ancient reservoirs in present-day Guatemala are revealing both the strengths and limitations of Mayan water science.
Although Mayan purification techniques resulted in very clean drinking water sources, archaeologists say the then-unknown consequences of a dark red pigment in current use will have systematically exposed the population to a toxic mercury poisoning.
The longevity of Mayan society It wasn’t a coincidence. This pre-industrial Central American civilization featured vast, densely populated urban centers, complex agricultural practices, and effective civic planning structures.
But, above all, the access to reliable drinking water it was an absolute necessity for these cities to prosper.
The city of Ucanalat the mouth of the Belize River, in northern Guatemala, probably housed between 8,000 to 11,000 inhabitantswhich required the maintenance of at least three nearby reservoirs, each with different uses.
Between 2018 and 2024, researchers from the University of Montreal, Canada, explored the archaeological remains around the Ucanal reservoirs.
The results, described in a series of recently published studies [, , ]demonstrate the huge effort employed to ensure that Mayan water sources remained as clean as possible.
The team focused on a trio of purpose-built reservoirs, designated Aguada 2, Aguada 3 and Swimming Pool 2.
Located on high ground, Aguada 2 included a natural filtration system composed of rocky entrance channels that retained harmful sediment and waste. However, the biggest advantage of the Aguada 2 was its ability to eliminate cyanobacteria.
Commonly known as blue-green algae, these toxic organisms continue to pose a problem for populations around the world. Their proliferations are also often large in scale, so the Mayans were fully aware of their existence and associated them with health problems.
«The Mayans knew about cyanobacteriaand these algae are clearly visible», explained the archaeologist Jean Tremblay, co-author of the studies, in a published by the University of Montréal.
«The Mayans could deal with the bacteria they could see», adds the researcher.
Additional surveys also indicated that the reservoirs were purposely surrounded by vegetation that provided shadethus keeping water temperatures lower and limiting the spread of cyanobacteria.
An analysis of carbon-nitrogen ratios revealed that any residual organic matter came from land plants and not algae present in the water. At the same time, the notable absence of phosphorus corroborates the theory that the ecosystem never suffered eutrophication — the process that leads to algal blooms.
In contrast, the Aguada 3located in a lower class area of Ucanal, presented contamination levels similar to those in polluted lakes of our days.
Researchers consider that this reservoir was used intentionally like a little trash cancontaining everything from household waste to broken pottery, and even including a desecrated human grave.
A Swimming pool 2 it was connected to a drainage channel of considerable dimensions that favored aeration and water circulation. Despite also being located in an urban area, this reservoir presentsto reduced contaminant levels.
The color of blood, life and death
But even with engineering feats rarely documented anywhere else at the time, the Mayans could only solve the problems they could see. THE I wasn’t one of them, unfortunately..
All the reservoirs studied by archaeologists had very high levels of mercury contaminationdue to , a pigment of bright red whose color derives from the mercury sulfidewhich was ubiquitous in Mayan society. It decorated buildings and objects of great value, as well as corpses and their funerary monuments.
«Its color evoked blood. In Mayan cosmology, blood, life and death are omnipresent», explained the archaeologist Christina Halperinco-author of the studies.
In the course of time, the cinnabar was washed away by the rain and infiltrated in the soil and surrounding waters.
But unlike a contaminant such as cyanobacteria, notably rrecognizable by the foul smellmercury runoff is colorless and odorless. Furthermore, degraded into sufficiently small particles to escape the reservoir filtration systems.
«They had no way of knowing it was toxic. It didn’t cloud the water or turn it red,” Tremblay said.
Increased regional trade over the years has provided wider access to religious objects, so that in Terminal Classic period (830–950 CE), mercury levels in reservoirs had increased by more than 300%.
«It wasn’t just the elites who used it — everyone was exposed», added Halperin.
Today’s toxicologists directly associate mercury contamination with disorders in children’s neurological developmentas well as complications in reproductive health.
Although the mercury levels discovered in Ucanal are alarming, they should not overshadow the informationnumerous wonders of the Mayan civilization. There was simply no way for people at the time to know or relate cinnabar to their well-being.
The more than 2,000 years of history of this society are testimony to its resilience and its store of knowledge. Tremblay summed it up concisely: “They didn’t live from day to day. That’s why your civilization survived 2,000 years».
