Toxic levels of a commonly associated pollutant with waste from modern industry were discovered in the midst of the most unlikely archaeological sites.
Long before conquistadors from distant lands ushered in the decline of war and disease, Mayan cultures sprinkled the floors of their urban centers with heavy metals. Mercury.
Levels of the element are so high in some areas that researchers are advised to prepare to save their health.
“Mercury pollution in the environment is typically found in contemporary urban areas and industrial landscapes,” says Duncan Cookgeoarchaeologist at the Catholic University of Australia and lead author of a study on the environmental legacy of the Maya.
Working with a team of researchers from the United States and the United Kingdom, Cook examined data sets collected from 10 Classic Period Maya dig sites and their surroundings, which included environmental measurements of mercury levels.
A comparison of readings from across the region identified seven of the sites reporting at least one area contaminated with a concentration of mercury that exceeds or equals modern benchmarks for toxic levels.
“Discovering mercury buried deep in the soils and sediments of ancient Mayan cities is difficult to explain, until we start to consider the archeology of the region which tells us that the Maya used mercury for centuries.”
In its pure form, mercury is a shiny gray metal that melts at a relatively low temperature, turning it into a thick fluid once commonly called mercury.
Yet throughout history, compounds containing mercury have had various uses in industry and culture. Among the most famous is mercuric nitrate, a substance used to stiffen the felt of hats that claimed poison the nervous system 19th century craftsmen who worked it.
Perhaps the most widely used form of mercury through the ages is crystalline mercury sulphide, a mineral also known as cinnabar.
Commonly found near hot springs and regions of volcanic activity, mercury pigment has been used as a purple coloring agent in artwork around the world since time immemorial.
For the blood-obsessed Mayans, cinnabar was more than a pretty shade of red.
“For the Maya, objects could contain ch’ulelor strength of soul, which resided in the blood,” said University of Cincinnati geoarchaeologist Nicholas Dunning.
“Therefore, the brilliant red pigment of cinnabar was a priceless and sacred substance, but unbeknownst to them it was also deadly and its legacy lives on in the soils and sediments around ancient Maya sites.”
Curiously, the limestone foundations upon which ancient Maya infrastructure was built do not provide the type of geology ripe for cinnabar production. To find a good source of ore, you need to travel to the far reaches of the Mayan world.
Archaeological studies suggest, in fact, that cinnabar was mined in Central America as early as the second to first millennia BC, a time when the Olmec culture flourished.
By the time the Maya were raising monuments to their gods across the land around the third century CE, cinnabar was already in common use, mostly in its powdered form to add color to decorative pieces, or even in the graves.
On rare occasions, the purified metal itself has been discovered, usually in association with ritual caches or elite burials. How the Mayans got their hands on this purified form of the element – whether through trade or their own methods of chemistry – remains a mystery.
How much this generous sprinkling of mercury sulphide affected the health of the Mayans is still not entirely clear, although a growing number of studies indicate that the toxic metal penetrated deep into their bones.
One of the last rulers of the Mayan city of Tikal, a king called Dark Sun, was notably obese, a potential clue to a metabolic disease often caused by mercury poisoning.
Past health issues aside, the researchers point to the need for today’s archaeologists to take precautions to protect themselves from the toxic metal as they dig through the multilayered history of the Maya culture.
“This result is further proof that, just as we live today in the Anthropocenethere was also an ‘Anthropocene Maya’ or ‘Mayacene’,” said Tim Beach, a geoarchaeologist from the University of Texas.
“The metal contamination appears to have been [an] effect of human activity throughout history.”
This research was published in Frontiers in Environmental Science.