Micro-CT scans reveal secrets of historical figurines

May 9, 2021
Anatomical figurines found in a Duke University collection appear to be made of true ivory. (Susan Churchill)

Anatomical figurines found in a Duke University collection appear to be made of true ivory. (Susan Churchill)

The vast majority of the historical anatomical figurines owned by Duke University are composed solely of true ivory, according to a new study using micro-CT scans to determine the figurines' composition and bring archaeologists one step closer to understanding the age, origins and possible uses of these artifacts. 

Duke owns the largest North American collection of ivory anatomical figurines, with 22 figurines in the collection out of 180 known figurines worldwide. A micro-CT examination of their material composition revealed that 20 of the figurines are made of true ivory, one is composed of antler, and one is composed of both ivory and whalebone components. 

The origins of these figurines and what they were used for remains unknown, but the findings of this research, published April 13 in Archaeological and Anthropological Sciences, contradict the theory that these figurines were used to train medical physicians.  

Ivory anatomical figurines, also called "manikins," are human statuettes with moveable arms thought to have been carved in 17th or 18th century Germany, according to the researchers. The torso acts as a lid, and it can be removed to reveal intricately carved organs inside the figurine. Historians have attributed these figurines to a family of craftsmen from southern Germany known to have worked with both horn and bone. 

"True ivory" refers to tusks or dentine material from elephants and mammoths, and the ivory used to make the figurines likely came from established 18th-century trade routes in northern Africa, according to the researchers. 

Compared with bone, ivory is less likely to crack when carved. Historically, this made elephant ivory preferable in the creation of artwork, but to the naked eye, ivory can look very similar to other materials, such as antler and bone.

To determine the composition of the 22 figurines at Duke, the researchers used micro-CT scans, the same technology used in medical CT scans but with a much higher resolution. This can provide information about an object's microstructure without destroying or harming the object, according to Fides Regina Schwartz, the lead author of the paper and an associate researcher at Duke. 

"It can show, in a very detailed way, how the structure of the bone or tooth is made," she said. "Ivory is basically the elephant's tooth, so it's a different material that is layered completely different than bone."

Between ivory, whalebone and deer antler, ivory is the most expensive material, and so it was a surprise that almost all of the figurines in Duke's collection are made of ivory, Schwartz said. 

"It would have been a lot less expensive and more accessible to make them from deer antler in the region that they stem from," she said. "So the fact that they were almost all ivory was pretty surprising to me."

The researchers point out that one ivory tusk in 1891 would have been priced at $713, which is equivalent to $20,857 today. In contrast, whalebone would have been priced at $5.28 per pound, which amounts to $150 today; and deer antler would have been locally available in Germany at the time, so antler would have been a much cheaper material than ivory or whalebone.  

Given how expensive ivory was, the researchers argue that these figurines were more likely "objects of curiosity and luxury status symbols in private collections … not intended for mass audiences," contradicting the theory that these figurines were used to train student physicians. 

"It would not make a lot of sense to have spent that much money to just train people where, in the time frame when those figurines were made, people would have had access to actual bodies of people who had died," Schwartz said. "Or, as far as I know, there were already wax models, so both of those would have been less expensive overall for the med schools to teach students with."

These findings are important for archaeology, art history and anthropology, according to Schwartz, not only in terms of what these findings reveal about the origins and uses of ivory anatomical figurines but also in terms of the techniques and tools offered by radiology, including micro-CT scans. 

The study shows that micro-CT scans can help determine the composition of fragile archaeological artifacts and help date them when carbon dating is not possible. Even if you "can't open something to look into it," Schwartz said, radiological techniques can help determine an object's composition in a way that "would be noninvasive through any artifact, and that might be important for archaeology as a whole."

The study "The art of imaging methods—using cutting edge radiological technology to uncover the secrets of ancient anatomical figurines," published April 13 in Archaeological and Anthropological Sciences, was co-authored by Fides Regina Schwartz, Susan Churchill, Rachel Ingold, Sinan Goknur, Divakar Gupta, Justin Gladman, Mark Olson and Tina D. Tailor, Duke University.

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