Sometime in the 15th century, a pair of girls, one aged nine and one 18, were sent on an arduous 745-mile journey to their deaths. The toxic pigment that colored the deep red clothing they were buried in might reveal more details of the story behind their final resting place.
Researchers have long hypothesized that the girls’ trek from the Inca capital of Cusco to Chile’s northern coast ended with a human sacrifice known as capacocha, a ritual intended to commemorate major events in the Inca emperor’s life or ward off natural disasters. But a few factors make the young women’s grave—unearthed in 1976 at the Cerro Esmeralda site in Iquique, Chile—different from other known capacocha sacrifices, Kristina Killgrove writes for Forbes. For one, the mummified pair—their bodies intertwined in fetal position, clad in blood-red garments, and interred alongside a rich array of silver ornaments, shells and metallic figurines—were found at a lower elevation than most high-status sacrificial burial grounds. But perhaps more unusual is the pigment found in the mummies’ clothing: its blood-red coloring comes from the mercury-containing mineral cinnabar, according to a new study published in the journal Archaeometry.
To identify the mysterious pigment found in the mummies’ clothing and in the tomb, a team of archaeologists led by Bernardo Arriaza of the University of Tarapacá conducted a series of chemical and microscopic analyses. Their findings confirmed the pigment as cinnabar, marking the first recorded instance of the mineral’s presence in Chilean burials and raising questions about the provenance and purpose of the toxic material.
According to the study, Inca inhabitants of the Andes region typically relied on hematite, an abundant iron oxide, to generate the red hues of their clothing and makeup. Cinnabar, a soft mineral found in sedimentary rocks located by volcanoes and hot springs, was more commonly used in rituals practiced by civilizations ranging from ancient Rome to Ethiopia, China and Spain. Unlike hematite, cinnabar is toxic to humans.
It’s possible the Inca were aware of the toxic side effects of cinnabar. If so, the mineral found sprinkled over the bodies had likely been scattered there in order to ward off grave robbers, drawing unsuspecting thieves in with its richly colored red hues.
Alternatively, Arriaza and colleagues note, cinnabar was often used in the Late Inca period by high-status women and warriors as face and body paint. While the Iquique mummies weren't painted, the cinnabar sprinkled onto their graves and used in their clothing could have designated status in the same way.
Despite the insights offered by the new study, much of the mummies’ history remains unknown. Although it’s likely that the young women were killed as part of a capacocha sacrifice, the lower elevation of the grave indicates it may simply be a traditional, albeit unusual, burial site. Science Alert’s Michelle Starr reports that the Incas’ only known source of cinnabar was the Huancavelica mine, located north of Lima and far from the burial site; the fact that the women’s contemporaries went to such great lengths to secure the dangerous pigment speaks to their probable prestige in Inca society.
Five hundred years after the Cerro Esmeralda grave was first sealed, the red pigment found inside remains dangerously potent. “Archaeologists need to be aware that beautiful red cinnabar contains mercury, posing hidden health risks,” the study states. “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.”