Is this shrunken head really human? The combination of imaging methods gives clues

There’s rarely time to write about every interesting science story that comes our way. So this year, we’re once again releasing a special series of posts on the Twelve Days of Christmas, highlighting a science story that fell through the cracks in 2020, each day from December 25 to January 5. Today: Sophisticated imaging methods can be used to authenticate whether shrunken heads (tsantsas) in museum collections are genuine.

In Tim Burton’s 1993 animated feature The Nightmare Before Christmas, there is a scene where a little boy receives a shrunken head as a Christmas present from Jack Skellington. Things are not going well, neither with the boy nor with his parents. But there was a time, in the early 20th century, when these macabre objects were in such demand among Western collectors that they sparked a lucrative market for counterfeits. Many museums around the world have shrunken heads (called tsantsas by the Shuar people) among their collections, but how can curators determine if these objects are genuine? Some sophisticated imaging methods can help, according to a paper published in August in the journal PLoS One.

The practice of headhunting and making shrunken heads has been documented primarily in the northwestern parts of the Amazon rainforest, as well as among certain tribes in Ecuador and Peru, such as the Shuar. Accounts conflict over specific details of the manufacturing process. But the tsantsas were usually created by removing the skull skin and flesh from the skull via an incision at the back of the ear, then discarding the skull. The nostrils were stuffed with red seeds and the lips sewn shut. Then the skin was boiled in water saturated with tannin-rich herbs for 15 minutes to two hours, so that the grease and grease floated to the top. It also caused the skin to shrink and thicken. Then the head was dried with hot stones and molded into something resembling human features and the eyes were sewn on. As a final touch, the skin was rubbed with charcoal ash – apparently to prevent the vengeful soul from escaping – and sometimes beads, feathers or other adornments were added for decoration.

Traditionally, the completion tsantas were posted on poles inside houses – uncarried, according to the authors of the August article, despite what one might read in the existing anthropological literature. Shrunken heads were a popular collectible among Victorian priests, Europeans, and American explorers eager to bring back exotic items for their private collections. Eventually a commercial market developed as the practice became more widely known after 1860. But these tsantsas were often made from the skins of animals (usually pigs, monkeys, or sloths), although some were made from human heads collected from corpses in morgues. The manufacturers nevertheless claimed that their wares were genuine.

Lauren September Poeta of Western University in London, Ontario, and her co-authors estimate that up to 80% of tsantsas currently held in collections around the world are of commercial origin, and there are very few reliable methods capable of determining their true origin. Conservators have generally relied on visual inspections or CT scans for authentication. But Poet et al. note that four key features are poorly resolved using standard CT: seam, eye anatomy, ear anatomy, and scalp anatomy. So they decided to see if they could improve the resolution of these features by combining computed tomography with high-resolution micro-computed tomography, an approach known as correlative tomography.

The team used a tsantsa from the collection of the Chatham-Kent Museum in Chatham, Ontario, acquired by the museum in the 1940s from a local family who had purchased it while exploring the Amazon basin. The only original note was that it was from the “Peruvian Indians”, and there was no definitive evidence that the Chathams tsantsa was the genuine article. The researchers performed a clinical CT scan of the whole object and two micro-CT scans – one of the whole head, the other a high-resolution scan of part of the scalp – using a machine from the Ontario Museum of Archaeology.

Poeta and his colleagues have confirmed that the Chatham tsantsa is made of actual human remains, although they could not determine whether it was ceremonial or commercial fabrication. The rough cut at the back of the skull and the use of double concealment is consistent with the first, but modern thread has been used to stitch the incision, eyes and lips, suggesting commercial production. “In fact, the distinction between ceremonial and commercial making may be more difficult to define than is commonly believed, because the practice of making tsantsas likely exists on a spectrum rather than an either/or dichotomy,” the authors wrote.

We could learn more by submitting tsantsas of known provenance to the correlative tomographic imagery. The authors concluded that while conventional computed tomography remains useful for reconstructing a baseline visualization of these fascinating artifacts – allowing researchers to examine them closely without risking damage from repeated manipulations – micro-computed tomography can determine whether a tsantsas is made of human materials and provides higher resolution detail for specific features.

DOI: PLoS ONE, 2022. 10.1371/journal.pone.0270305 (About DOIs).