For the ancient Maya, the vibrant red mineral cinnabar held deep sacred meaning, representing blood, life and the soul. They used it widely as pigment in murals and temples while also employing it in ceremonies and funerary rites. What they did not know is that cinnabar is mostly mercury, which can be highly toxic.
Previous research showed how mercury from cinnabar left enduring contamination at the sites of certain ancient Maya cities such as Tikal in Guatemala. A new study reveals that this contamination was more widespread than previously known and documents how mercury, after leaching into the surrounding soil and bodies of water, proved deadly for many aquatic organisms.
Researchers obtained core samples from beneath lakes at two ancient Maya cities on Mexico's Yucatan peninsula — the well-studied site of Coba and the little-known site of Xcach.
The samples showed a mercury spike at Coba beginning around 250 AD and lasting about 150 years around the outset of the golden age of Maya civilization, called the Classic Period. At Xcach, there was a spike from around 125 AD to 200 AD, shortly before the Classic Period, then a second spike at about the same time as the one at Coba, and a third spike from about 535 AD to 820 AD, running to around the end of the Classic Period.
The study documents mercury contamination in the Maya northern lowlands, a region with previously sparse mercury records, and reveals some of the highest recorded Maya-era mercury concentrations.
Many of the great Maya cities collapsed and were abandoned at the end of the Classic Period. Varying hypotheses have been presented to explain this calamity, including climate change and warfare. The new research suggests mercury poisoning as one additional factor.
"Our study shows that modern toxicology and pollution regulations were far exceeded at the most toxic levels for centuries around Coba and Xcach," said paleolimnologist Matt Waters, a professor of environmental science at Auburn University in Alabama and lead author of the study published in the journal Science Advances.
"Furthermore, we measured multiple biological markers in the sediments for bacteria, algae, cyanobacteria, shelled organisms and insect midges, which all decreased or vanished in the lakes, meaning the mercury had made its way into multiple levels of the food chain," Waters said.
MERCURY POISONING
Mercury in people can harm the central nervous system, brain, kidneys, lungs and heart.
"While we do not show this in our sediment records, this trophic movement implies that the Maya people might have been exposed to mercury via consumption of water or fish," said study co-author Savanna Wooten, a postdoctoral researcher at the Jones Center at Ichauway research facility in Georgia.
"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," Wooten said.
Coba (pronounced "koh-BAH") is estimated to have had a population of 60,000 to 90,000 people during the Classic Period. It is a well-known jungle archeological site visited by many tourists that features one of the tallest ancient pyramids in the Yucatan.
Less is known about Xcach (pronounced "SCOTCH"), a site on private land featuring multiple pyramids and structures where very little archeological work has been done.
Cinnabar is a naturally occurring mercury sulfide mineral and may have been a major trade commodity in places like Coba and Xcach where it is not found in natural abundance, the researchers said.
The Maya fashioned one of the great civilizations in the pre-Columbian New World, prospering in a broad area of Mexico as well as Guatemala, Belize, Honduras and El Salvador. Among other achievements, they built monumental structures, crafted great works of art, gained a sophisticated understanding of astronomy and mathematics, produced an advanced calendar and developed an intricate writing system.
"Their longevity as a culture and development in science, construction and art is both extensive and elegant. Cinnabar would have been a pigment that added beauty and culture to these people," Waters said.
