Scientists have encountered a toxic substance on textiles buried with two Incan mummies sacrificed in Chile. Since making the find, they’ve warned other researchers to be wary of handling any similar red pigments. Why did the Inca people put something so dangerous in the burial?

As Live Science reports, the vibrant red textiles that were placed in the grave of two female mummies buried between 1399 to 1475 AD, were tinted with cinnabar, a primary source of the highly toxic metal mercury. This is the first known example of ancient peoples in northern Chile having used the pigment.

Detail of the restored textiles. (Museo Regional de Iquique)

The results of this research were published in the journal Archaeometry. In it, the researchers explain that most of the Andean societies who lived during that time used hemaтιтe to color their textiles red because it “provides strong hues, has tinting strength and good opacity and, furthermore, can be easily ground and finely pulverized.” However, they also write that cinnabar was used since the time of the Chavin Culture to paint some significant artifacts made of gold or wood. The pigment was also placed in some tombs as a ritual offering; in general, it was always used “in prestigious and elite social contexts.”

This social value for the red pigment provides some insight on how it may have come to be in the burial. When the mummies of the two finely dressed young females (one aged nine years old and the other between 18-20) were found in 1976 in Cerro Esmeralda, 104 artifacts were found alongside their bodies. Some of the grave goods included well-made ceramic vessels, Spondylus shells, bags, silver ornaments, and small anthropomorphic and zoomorphic metallic figurines. According to Jorge Checura, the first researcher to describe the burial, the girls were probably from Cusco, meaning their trip to their final resting place would have taken months to complete.

Some of the grave goods placed with the Incan mummies. (Museo Regional de Iquique)

Archaeologists decided that the bodies were probably buried following an important ritual Inca sacrifice, called capacocha (Qhapaq Hucha). Although there is still debate on the topic, it is generally believed that the Inca people completed this ceremonial sacrifice when they were going through difficult circumstances, such as the death of the Emperor, a period of bad harvests, or as a response to a natural disaster. As the study’s authors write: “We need to keep in mind that capacocha sacrifices were performed in commemoration of historical events in the life of the Inca emperor or in response to natural catastrophes.”

Illustration by Felipe Guaman Poma de Ayala (1615). This image may depict the ritual of Capacocha. National Library of Denmark. (Public Domain)

It is believed the two Incan mummies found at Cerro Esmeralda may have been sacrificed to celebrate local people entering the Inca Empire, Tawantinsuyu.

View of Iquique from Cerro Esmeralda, Chile. (Museo Regional de Iquique)

Several studies have been conducted on the two mummies since they were discovered, and there was even an inkling before that the red pigment in the mummies’ clothing may have been cinnabar, but it is only now that researchers from the University of Tarapacá in Chile have used chemical and microscopic investigation to conclusively name the substance.

The cinnabar found in the grave of the Chilean mummies came all the way from Huancavelica, north of Lima in Peru, the only known mine for this pigment during Incan times.

Considering the dangers ᴀssociated with cinnabar, the study’s authors write “it is evident that the ritual handling and use of cinnabar colour during the Inca Period required specific knowledge and had an important social meaning.” Thus, it has also been suggested that the Inca people may have deliberately placed the pigment in the burial to deter or punish any possible grave robbers.

Cinnabar contains the toxic metal mercury. ( H. Zell/CC BY SA 3.0)

Whether the original purpose was solely ritual or perhaps as a deterrent as well, handling the artifacts containing cinnabar could still be lethal today if proper precautions are not taken. That’s why the study’s authors have warned other researchers to always take extra care when they encounter similar red pigments – even if they haven’t found cinnabar in the area before, “It may cause a range of health problems affecting the nervous and muscular systems and the gastrointestinal tract, among others, and even death in cases of extreme exposure.”

Today, the grave goods from the Cerro Esmeralda burial are stored at the Museo Regional de Iquique (MRI).