The Maya’s Love of Red Paint May Have Had a Deadly Consequence Nobody Knew About

Ancient lake mud reveals a toxic legacy behind the Maya's sacred red pigment.

For the ancient Maya, red was the color of life. They painted walls, decorated sacred objects, and even covered the dead with brilliant red pigment. But little did they know, this red was poison.

A new study of Mexico’s Yucatán Peninsula reveals severe mercury pollution spanning centuries of Maya occupation. In one lake, concentrations reached nine times a benchmark for serious harm to aquatic life. As mercury rose, microorganisms dwindled, tiny shelled animals disappeared, and food webs unraveled.

The mercury was most likely imported in the region and sourced from the pigment cinnabar. Across the Atlantic, the Europeans weren’t any wiser.

Since ancient times, European, Asian, and Mediterranean artists prized cinnabar (vermilion) for its brilliant crimson color. Roman emperors painted their faces with it during triumphs, and wealthy Romans used it for lavish frescoes, such as those preserved in Pompeii. The Romans mined cinnabar at Almadén in Spain using forced labor, where enslaved workers routinely died from acute mercury poisoning. Ancient Europe also made extensive use of red lead (minium), a synthetic lead oxide pigment that exposed painters, scribes, and artisans to chronic lead toxicity.

A Toxic History Buried Beneath the Lakes

Cinnabar is a brilliant red mineral made of mercury sulfide. Scarce in the northern Yucatán, it likely arrived through long-distance trade. The Maya also occasionally used liquid mercury.

Matthew Neal Waters of Auburn University and colleagues extracted sediment cores from Lago Cobá, beside a major Maya city, and Cenote Xcach, a sinkhole lake near a little-excavated settlement.

The cores, collected in 2023, preserved layers of mud deposited over more than 2,000 years, which acted like a sort of time capsule, allowing the researchers to estimate how much mercury pollution there was in the lake at different points in history. Researchers dated the layers using charcoal and wood fragments, then tested them for mercury.

At Cobá, concentrations began rising around A.D. 40, reached about 2.3 parts per million around A.D. 250–300, and returned near natural levels by approximately A.D. 520.

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Xcach was much worse. After two earlier pollution episodes, mercury surged again between approximately A.D. 535 and 820. It peaked around A.D. 720 at 18 parts per million, nine times the threshold of 2 parts per million at which severe effects on sediment-dwelling organisms are expected.

For roughly 275 years, concentrations at Xcach remained above that severe-effect threshold.

Two other lakes sampled by the team lacked comparable spikes, which rules out a region-wide atmospheric source due to some natural phenomenon. The researchers suspect that mercury used on land during Maya activities was washed into the lakes with eroded soil, although they could not establish whether cinnabar, liquid mercury, or both were responsible.

When the Lake’s Smallest Creatures Disappeared

The chemical readings were startling, but the rest of the evidence was even more disturbing.

At Cobá, an entire section of polluted sediment contained no preserved shells from ostracods — tiny crustaceans — or freshwater snails. Their shells were abundant in other layers, so one might suspect that the mercury pollution wiped out these creatures while concentrations were high.

Researchers had noticed this unexplained disappearance in an earlier sediment core collected in the 1990s, but only now with the new mercury measurements do we have a plausible explanation.

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At Xcach, fossil remains of nonbiting midge larvae declined sharply. One previously dominant type, Goeldichironomus, nearly vanished, replaced by another, Beardius.

Pigment markers of algae, cyanobacteria, and purple sulfur bacteria also fell dramatically when mercury reached toxic levels.

What makes this particularly interesting is that phosphorus, a nutrient that usually encourages algal growth, was still entering the lakes. Initially, some microorganisms flourished. But as mercury accumulated, their traces collapsed despite the continued supply of nutrients.

“The biological community completely changed,” Waters said.

Overall, the Maya and their love for red ultimately triggered widespread ecological disruption. Previously, a 2020 study at Tikal, in Guatemala, identified mercury and toxin-producing cyanobacteria in ancient water reservoirs. A 2022 review found mercury concentrations meeting or exceeding modern toxicity benchmarks at seven of ten studied Maya sites.

Could the Pollution Have Harmed the Maya Themselves?

The Maya relied on fresh water for drinking and fishing. Mercury can accumulate in aquatic food chains, potentially exposing people who eat contaminated fish or shellfish. Chronic exposure can damage the brain, nervous system, kidneys, and other organs.

Could mercury pollution have contributed to the collapse of Classic Maya civilization?

Between roughly A.D. 750 and 900, many powerful Maya cities in the southern lowlands, including Tikal, experienced a dramatic decline. Royal dynasties fell, monumental construction slowed or stopped, and populations dwindled as people abandoned major urban centers. Historians call this the Classic Maya collapse, although it unfolded unevenly over generations. Northern centers such as Chichén Itzá continued to flourish.

Researchers have linked these upheavals to prolonged droughts, warfare, environmental degradation, and political instability. Now, mercury pollution may be another piece of the puzzle.

“This research does little to link mercury directly to the demise of Classic-era Maya cities. But it does add one more stressor to the growing list of environmental and climatic pressures documented to have co-occurred with the Classic Period Maya,” co-author Savanna Wooten told Reuters.

At Cobá, contamination subsided centuries before the end of the Classic Period. At Xcach, it persisted into the eighth and ninth centuries, when many Maya cities were undergoing profound changes.

While it’s highly unlikely that a humble red paint brought down Maya civilization, the new findings reveal another form of collapse, which is perhaps just as unsettling: a substance cherished for its beauty and sacred significance may have degraded the waters and food resources on which entire communities depended.

The findings were reported in the journal Science Advances.