A young woman who lived and died more than 2,000 years ago left behind remains in China that are unlike any we've seen previously.
On her teeth, archaeologists found traces of cinnabar, the brilliant red form of mercury sulfide. Because of the mercury content, this mineral is toxic; never before have human remains been found with teeth stained with the stuff.
What's even more interesting is that, although cinnabar and other red pigments are found often in burial contexts, and were used for shamanistic purposes, a team led by Sen You of Jilin University in China believes that, in this case, the cinnabar was used during the young woman's life.
They have named her the Red Princess of the Silk Road.
"It is believed that cinnabar was mixed with binders, then used to stain the teeth of this young female during pre-mortem life," the researchers write in their paper.
"This is the only known case of intentionally staining teeth red using cinnabar, a bio-toxic substance. Even though this is an isolated case, its significance could be discussed not only in the context of its particular time and location but for human culture in general."
The remains of the unnamed woman were discovered at an archaeological site called the Shengjindian cemetery in Xinjiang, along the ancient Silk Road that our forebears traveled to trade goods and migrate great distances around Asia and Europe for well over a millennium.
The cemetery was excavated in 2007 and 2008, yielding a total of 31 tombs and many rich grave goods, such as silk, pottery, gold and bronze artifacts, and glass and onyx beads.
The Red Princess, who may not have actually been royalty, was found in a tomb with the remains of three other people, including a child. She was just 20 to 25 years old when she died, between 2,200 and 2,050 years ago.
What intrigued the archaeologists were the traces of red found on her teeth. There are several different substances that can be used as red pigment, including cinnabar, hematite, and ochre, so they had to conduct tests to find out what it was.
They used Raman spectroscopy to identify the substance as cinnabar, and X-ray fluorescence spectroscopy to confirm the identification, and rule out environmental contamination.
Fourier transform infrared (FTIR) spectroscopy analysis – a widely used method in research – then identified the presence of a protein substance probably used to bind the color to the teeth.
It's not known exactly what this binding agent was made of, but such binders in ancient China were relatively common, and usually consisted of animal material, such as collagen, egg white, or milk.
It's also not clear why the young woman stained her teeth red, which has been considered an important and auspicious color in China for a long time. The practice may have had a spiritual reason.
As the researchers point out, cinnabar had a pretty prominent role in shamanistic practice, as well as traditional medicine, and has psychoactive properties that may have made it useful as a hallucinogen.
On the other hand, the reasons may have been cosmetic, as blackened teeth later became popular across Southeast Asia and Oceania. The woman's red teeth may have denoted status, as her burial in the cemetery further suggests.
This is emphasized by the fact that cinnabar was not a local commodity. There are no natural deposits of it in the region the woman was buried in, so it had to have been traded. The closest sources of cinnabar would have been Central China, the Near East, and Europe.
"Considering the geographic distribution of cinnabar and the identity of its users, the social identity of the tomb owner may have been unusual enough to access this precious resource," the researchers write.
"More investigations and discoveries are warranted to test these hypotheses."
The research has been published in Archaeological and Anthropological Sciences.