X-rays reveal the faded colors of a 1,300-year-old Inca idol

The idol of Pachacamac was already 700 years old when Spanish conquistadors arrived in Peru, according to radiocarbon dating of the wood. People journeyed from all over the Andes to consult the statue, believed to be an important oracle of the Inca gods, leaving behind offerings of gold, silver, and valuable fabrics. In 1533, Spanish conquistador Francisco Pizarro ordered his followers to knock the oracle from its pedestal in front of horrified onlookers. Centuries later, microscopes and X-ray fluorescence shed light on the lost colors of Inca religious life.

Long-lost colors

After roughly 1,300 years, the carvings on the surface of the oracle still survive in rich detail. Two people in elaborate clothing stand side by side in the top section; one wears a headdress of feathers, and the other wears a snake headdress. On the much taller middle segment, richly attired people mingle with jaguars, two-headed snakes, and an assortment of human-headed animals, interspersed with geometric designs. The base is blank and probably once fit into a hole in a pedestal. But as elaborate as the carvings are, they’re missing something important: color.

Much of the color of the ancient world has been lost to us for centuries, and modern technologies are only starting to show us how vivid the past really was. Greek and Roman statues weren’t sterile white; medieval cathedrals were full of color; and the animals, spirits, and people carved into the wood of the Pachacamac Idol once stood out in vivid red, white, and yellow.

With the naked eye, no trace of color lingers on the statue, but under a microscope, tiny traces of red, white, and yellow pigment still cling to the carved surface, even after 1,300 years. The two upper figures’ headdresses were once vivid red and yellow, while their faces were painted red and white. Bits of red and yellow pigment still cling to some of the animals and people in the middle segment.

“It may have even included additional painted colors that have not been preserved,” wrote archaeologist Marcela Sepúlveda of the University of Tarapacá, Chile, and colleagues in a recent paper.

They used a non-destructive technique called X-ray fluorescence (XRF) to examine those traces and learn what the pigments were made of. Each chemical element emits in a slightly different wavelength of light when it’s bombarded with X-rays; by measuring those emissions, researchers can map the presence of different elements on an object’s surface.

An expensive paint job

The XRF study revealed centuries of dirt in the carved recesses and crevices of the statue, along with a thick layer of varnish over the wood. Beneath the varnish, however, the yellow pigment contained mostly iron, which means it was probably made with a type of iron oxide. The white contained calcium and sulfur, and Sepúlveda and colleagues say it was probably made with gypsum, although they can’t rule out other options. But the red was especially interesting because areas of the statue with traces of red pigment contained mercury and sulfur, the chemical signature of a red mineral called cinnabar.

Based on artifacts at other sites around the Andes, along with descriptions in historical texts, we know that people in pre-Columbian Peru used cinnabar as a red pigment to decorate important objects and murals, as body paint for warriors in battle or nobility in important ceremonies, and as offerings to idols and effigies like the Pachacamac Idol. Cinnabar was the high-end option for painting things red; more ordinary projects made-do with simple iron oxide.

But for people at Pachacamac, the nearest source of cinnabar was about 350km (220 miles) away at the Huancavelica mine in the central Andes. Transporting cinnabar long distances for a specific purpose wasn’t unheard of in pre-Columbian Peru, so the discovery wasn’t shocking. However, it does emphasize how important the idol must have been to the people who carved and painted it and set it up in the temple.

Who carved the idol?

The carvings match the style and motifs favored by the Wari culture, which preceded the Inca in parts of Peru. Radiocarbon dating confirms that the wood was cut sometime between 760 and 876 CE. Based on archaeological excavations, Pachacamac began as a settlement around 200 BCE and gradually grew into a 450 hectare city with palaces, a large cemetery, and a major temple complex. Traces of the Wari culture remain in the architecture of buildings at the site, and in imagery like that carved on the idol.

But then the Inca Tupac Yupanqui conquered the region around Pachacamac, adding it to the Tawantisuyu Empire. As in their other territories, the Inca imposed sun worship as the primary religion, but they didn’t expect people to abandon their own gods. So under the Inca, people at Pachacamac kept consulting the Oracle as they had for centuries, even as the Inca built the site into a major pilgrimage center to help emphasize their own power. By the time the Spaniards arrived, the oracle resided in a dark vault in an upper chamber of the Painted Temple, one of two major temples in Pachacamac—and that’s exactly where archaeologists found it in 1938.

“The fact that it was cared for over time despite possible changes in the ceremonial practices at Pachacamac serves to emphasize the significance of the Idol,” wrote Sepúlveda and colleagues.

It wasn’t dried blood

By the time the Spaniards arrived, the carved statue may already have lost much of its color over the centuries, since the conquistadors describe the wood as dirty, not painted, except for one mention of “dried blood” in its crevices. That turned out to be cinnabar, likely from the same mine that later supplied the mineral for the Spaniards’ silver processing.

Although the Spanish colonial rulers destroyed many Inca statues, ceremonial objects, and murals in their efforts to wipe out indigenous religion, enough has survived to give us small glimpses into the colors of Inca religious life. Remains of murals in the Temple of the Sun and the Painted Temple at Pachacamac display people, marine life, and geometric patterns in black, green, red, white, and yellow.

But we don’t yet know much about what those colors meant to the people who worshipped there. Perhaps color had symbolic meaning in certain contexts, or perhaps the architects of Wari and Inca temples used colors to evoke certain moods in the visiting faithful. It’s difficult to say without further information.

Today, the idol is a unique and important piece of Peru’s indigenous heritage—exactly the kind of thing that’s difficult to subject to destructive tests like radiocarbon dating. In this case, the statue had a natural hole in the blank lower section, and Sepúlveda and colleagues took a small sample from that for radiocarbon dating and microscopic analysis. The XRF used to study the pigment is nondestructive but offers less detail about the chemical composition of the pigments than other methods—but those other methods would require removing small samples of the pigment, which Sepúlveda and colleagues opted not to do “to preserve the traces that remain on this unique object.”

PLOS ONE, 2020. DOI: 10.1371/journal.pone.0226244 (About DOIs).

https://arstechnica.com/?p=1645131