The Nun with Blue Teeth

I’m always looking for skeleton stories.  But it’s not often that I come across an article in the scientific literature that includes references to the ancient Greek physician and herbalist Dioscorides (ca. 40-90 CE) or the medieval abbess and scholar St. Hildegard of Bingen (1098-1179).  So this open-access article in Science Advances, “Medieval women’s early involvement in manuscript production suggested by lapis lazuli identification in dental calculus” immediately caught my attention, as well as the attention of a number of media outlets.  What’s the big deal?

In a nutshell, the article argues that the teeth of a 1000 year old German nun contained a rare blue pigment.  The authors of the Science Advances article used carbon dating, genetics, and osteological analysis to determine the age of the skeleton that had been dug up at the site of a medieval monastery, as well as the age and gender of the individual whose bones they were.  Modern archaeology, particularly if it deals with human remains, involves a lot more than simply digging things up.  Carbon dating, developed by nuclear scientist Willard Libby in 1949, analyzes the decay of radioactive carbon-14 (14C) in dead organic matter – plants or animals.  Since 14C decays at a known rate (it has a half-life of about 5,700 years), carbon dating immediately became a vastly more accurate method of dating human and animal remains than earlier comparative techniques.  But it requires chemical analysis of a piece of bone or other organic material.  In this case, the skeleton was dated to 997-1162 CE.  Analysis of ancient DNA (aDNA), (the topic of this recent New York Times Magazine article), can tell us all kinds of things about ancestry and disease.  But the main analysis in the Science Advances article looked at something much more prosaic:  dental tartar.

Dental tartar or calculus, as my hygienist reminded me this morning as she scraped my teeth (“Let me know if that tingles”), is composed of bacteria in our mouths that stick to our teeth.  Over time, it chemically changes and calcifies, becoming stony.  Basically, it fossilizes. It also contains remnants of everything we’ve eaten, and also some things we may have breathed in, such as pollen; it’s kind of like a core sample of the body.  Medieval dental care was rudimentary by our standards; according to co-author Christina Warinner (whose former grad student, Anita Radini, made the discovery), who was recently interviewed for the Science podcast, apparently our medieval nun, aged around 50, had at least 24 years of tartar on her teeth.  Therefore tartar analysis can tell us all kinds of interesting things about diet as well as about local plants.

In this case, the analysis also found something weird, flakes of a bright blue pigment that certainly did not come from food.  Further chemical and spectral analysis revealed that the particles were made of lapis lazuli,

credit: Hannes Grobe

an expensive and rare stone that was mined mainly in Afghanistan.  Lapis lazuli had a number of uses in the Middle Ages, including in medicines, but its main use, because of its amazing bright blue color, was as a pigment, in its ground form known as ultramarine.  The Science Advances authors point out that its expense – not least because it had to be imported from Afghanistan, an arduous journey in the 11th century – meant it was used in only the most luxurious manuscript illumination, along with gold and silver.

How did this nun get lapis lazuli in her teeth?  The authors propose four scenarios: the woman was involved with pigment production – grinding the lapis lazuli stone to make ultramarine – and somehow inhaled some of it  (the authors actually tried this themselves, and did get some particles in their mouths).  Another possibility is that lapis was somehow ingested for medicinal purposes, but there is no historical evidence of this use of lapis lazuli in Germany in the 11th century.  A third possibility – I must admit my favorite – is that our nun was a devotee of what is known as “devotional osculation”; that is, she liked to kiss the holy images in her books (this article describes this practice).  This practice became very popular in the 14th century, so much that some illuminated manuscripts have the images kissed right off.  But it was not at all common in the 11th century.

The authors therefore conclude that our nun was in fact an artist, who illuminated books herself, and a highly skilled artist who was trusted with such rare pigments as ultramarine.

This 12th century nun named Guda was one of the few women who signed their illuminated manuscripts. OBERLIN.EDU/WIKIMEDIA COMMONS

She could have gotten blue pigment on her teeth by the very common practice of licking her paintbrush or pressing it between her lips to make a finer line.   Centuries later, this practice had fatal consequences for women who painted radium dials on clocks in the early twentieth century, as detailed in Kate Moore’s recent The Radium Girls.  Our idea of a medieval scriptorium has been deeply influenced by fictional accounts such as Umberto Eco’s 1980 The Name of the Rose that depicts an all-male monastery cut off from the world.  But women’s monasteries existed alongside those of men; the place where the skeleton was found, in Dalheim in west-central Germany, contained both male and female monasteries, although no trace of the women’s monastery remains.  And, as the work of one of the article’s co-authors, Alison Beach, has shown, there is increasing evidence that women served as scribes and illuminators as well as men.

I loved this article, which is a wonderful combination of history and science, showing that even the smallest detail in skeletal remains can contains volumes of information about the past.  It did make me wonder, though, if in our devotion to twice-yearly teeth cleaning, we are not depriving future archaeologists of critical information about us.