Nowadays, mercury is a cause for concern for health and environmental authorities in practically every country. Laws have been passed and programs implemented for its complete elimination from human activities. But it wasn’t always this way: mercury and its compounds have been highly prized and used since ancient times worldwide for various purposes ranging from decorative to medicinal, metallurgical, and symbolic.

In particular, cinnabar (mercury sulfide), a mineral of intense red color, has been considered in many cultures as an exotic raw material, highly valued and associated with elites and sacred practices. A recent study examined one of these cases, which occurred almost 5000 years ago in the Copper Age of the Iberian Peninsula, investigating mercury exposure through human bones.

The analysis included a total of 170 samples from 70 human individuals and 22 animals (plus one soil sample) from the Copper Age site of Valencina de la Concepción (Seville), in southwestern Spain. It is the largest study conducted at a single site on mercury exposure combined with cinnabar use based on human bones.

Main Iberian sites with THg measurement in human bone mentioned in the text (in red, sites with evidence of cinnabar).
Main Iberian sites with THg measurement in human bone mentioned in the text (in red, sites with evidence of cinnabar). Credit: Manuel Eleazar Costa Caramé and Raquel Montero Artús / Journal of Archaeological Method and Theory

Abnormally high values were recorded in some individuals dating between 2900 and 2650 BC, especially those buried in notable tombs belonging to the social elite of that period, but high levels of mercury were also found in the rest of the population.

These high concentrations of mercury in Valencina represent one of the most intense and prolonged cases of exposure to this element recorded in human history, making it an important site for assessing the long and complex history of the use of this substance.

Cinnabar, often mixed with other mineral substances and organic binders, has been used as a pigment for millennia to paint rock surfaces, buildings, artifacts, textiles, or even the human body. In many cultures, cinnabar and mercury have also been used for medicinal, magical, or life-prolonging purposes.

Great Chamber of Montelirio: cinnabar dust on human bones
Great Chamber of Montelirio: cinnabar dust on human bones. Credit: Álvaro Fernández Flores

Its use as a medicinal or magical drug is well attested. The alchemists of the court of the first Chinese emperor Qin-Shi-Huang, in the 3rd century BC, sought the secrets of immortality in liquid mercury. Western medicine made use of oral doses of mercury salts until the 20th century to treat various ailments.

In the Iberian Peninsula, there is an ancient and extensive record of the use of cinnabar and mercury, reflected in substantial literature. The prominence of both minerals is explained by the presence in Almadén (Ciudad Real) of the world’s largest mercury mine, included in the UNESCO World Heritage List in 2012.

The earliest evidence of cinnabar use in the Iberian Peninsula dates back to the early Neolithic, around the 6th millennium BC. In the 4th and 3rd millennium BC (Late Neolithic and Copper Age), cinnabar has been found in numerous funerary contexts, either sprinkled on floors, bodies, and tomb offerings or used as pigment to paint the orthostats and lintels of megalithic monuments.

Cinnabar powder pulverized on Structure 10.049
Cinnabar powder pulverized on Structure 10.049. Credit: José Peinado Cucarella / Miriam Lucianez Triviño

In Valencina, the use of cinnabar was particularly intense between c. 2900-2650 BC, in the first of the site’s two main development phases. In this phase, Valencina witnessed intense monumentalism as part of sophisticated ritual and funerary practices often involving finely crafted objects with exotic raw materials.

In the tomb of “The Ivory Lady” and in the tholos of Montelirio, an elite funerary monument, cinnabar had a pervasive presence. It was used to cover and paint the large slate slabs lining the corridors and chambers and was abundantly sprinkled over the bodies and grave goods.

The data collected in the study reveal that the Copper Age population of Valencina suffered one of the most dramatic cases of human exposure to mercury known in history.

Several types of exposure can be discerned: The first would have affected a small group of religious specialists and elite members who may have inhaled or consumed cinnabar as part of their lifestyle. The second exposure would have affected a larger, but still small, contingent of people involved in obtaining and processing cinnabar. A third type of exposure, which affected a much larger group (perhaps the entire population inhabiting or frequenting Valencina), would have been indirect, resulting from the presence of mercury in the environment or from contamination caused by sustained manipulation of cinnabar over several decades.

Cinnabar
Cinnabar. Credit: H. Zell / Wikimedia Commons

The main effects of mercury include cardiovascular toxicity, reproductive and developmental toxicity, neurotoxicity, nephrotoxicity, immunotoxicity, and carcinogenicity. The effects vary depending on the chemical form of mercury and the route of exposure.

The Valencina population studied here must have suffered some, if not most, of the described symptoms, such as neurological, motor, respiratory, cardiac disorders, etc. The exceptional concentrations found in the bones of some elite women may have resulted from the inhalation, accidental or deliberate, of mercury vapors when heating cinnabar.

These women are believed to have been religious specialists in charge of an important sanctuary. The neurocognitive, motor, and behavioral disorders caused by mercury poisoning, in many ways similar to those of hallucinogenic drugs, may have been a sought-after feature among this highly specialized group involved in mystical practices, dramatic ritual appearances, and political governance.

Even if the prevalence of such practices was relatively short-lived, cinnabar processing must have demanded a workforce dedicated to its acquisition, processing, and manipulation, leading to the exposure of a substantially larger number of people. The inevitable fine cinnabar dust may have settled on the surrounding soil and vegetation, later entering the food chain and affecting an even wider part of the population.

Sources

García Sanjuán, L., Montero Artús, R., Emslie, S. et al. Beautiful, Magic, Lethal: a Social Perspective of Cinnabar Use and Mercury Exposure at the Valencina Copper Age Mega-site (Spain). J Archaeol Method Theory (2023). doi.org/10.1007/s10816-023-09631-8

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