Saturday, October 1, 2022

New scanning method will unlock secrets of shrunken heads

A new scanning method will help to identify the origin of shrunken heads from South America in museum collections, assisting ethical curation and repatriation efforts, experts say.

Fist-sized tsantsas are commonly held in collections in Europe and North America. However, it is often unclear whether they were created from human heads for ceremonial purposes, or made from animal or human remains for the large commercial market that was fuelled by explorers, missionaries and tourists.

There has been increasing interest in understanding the origins of tsantsas in recent years as they have been removed from display in many museums — including the Pitt Rivers Museum in Oxford — as part of decolonisation efforts. The heads were a popular attraction but were often described by visitors as “gory” or “gruesome” and the work of “savages”. There are now ongoing discussions around returning tsantsas to South America.

The tsantsa in the Chatham-Kent Museum, Canada, studied by the team

Authentic, ceremonial tsantsas were created by the Shuar and Achuar people of Ecuador and northern Peru, possibly from the 1500s or earlier. Production ceased after the Shuar and Achar came under increasing pressure from European settlers, the Church and colonial authorities during the 19th and early 20th centuries. The same missionaries and colonists, alongside travellers, drove the market for commercially-produced tsantsas, which could be sold as “authentic” artefacts.

Tsantsas were traditionally said by anthropologists to have been made from the heads of enemies killed in battle, in an attempt to trap the avenging souls of the deceased. However, recent studies engaging with Shuar communities indicate that tsantsas were also made from heads of clan leaders who died from natural causes, and were intended to harness their power positively. The heads were displayed inside houses or on poles.

Until now, tsantsas in collections have generally been assessed through visual observation and by using clinical computed tomography (CT) scans, as widely used in healthcare. However, researchers in Ecuador and Canada say that clinical CT scans do not provide images of anatomical features of adequate resolution to determine conclusively whether a tsantsa was made from a human head.

The resolution is also insufficient to show fine details such as the stitching of the eyelids, lips and at the back of the head, which can give clues to whether a tsantsa was an authentic, ceremonial one.

Ceremonial tsantsas were created in a process that involved removing the skull through an incision at the back of the decapitated head. The skin was boiled for around 15 minutes to two hours and the inside surface was then scraped to remove connective tissue. The eyes and lips were normally sewn shut with palm fibres while the skin was turned inside out.

To shrink the skin, small rocks and then hot sand were then heated over a fire and rolled around inside the head, drawing out the remaining moisture. This heating continued until the head was about a quarter of its original size, or the size of a fist. Often, heated flat stones were then applied to the skin’s outer surface to “iron” it and burn away facial hair.

“Like many things ‘collected’ in the late 1800s and early 1900s, the context is sadly lacking”

Lauren September Poeta

Commercial tsantsas for the collecting market, on the other hand, were frequently made from the skins of animals such as monkeys, sloths and pigs, and stitched using modern thread and a different technique.

In their paper in the open-access journal Plos One, anthropologist Lauren September Poeta, of Western University, London, Ontario, and her co-authors, describe how they used micro-CT scans alongside clinical CT scans and visual observation to study a tsantsa held by the Chatham-Kent Museum in Chatham, Ontario. The tsantsa was donated to the museum in the 1940s by a local family who had acquired it while travelling in the Amazonian basin.

The micro-CT scan allowed the researchers to see anatomical features such as the ear canal that were not clearly visible in clinical CT scan, proving that the head was human.

Micro-CT visualisation of the incision and stitching at the back of the Chatham tsantsa, removing the hair

However, the micro-CT scans, which were approximately 6.5x and 36x higher resolution than the clinical scan, also indicated that the lips and eyes were stitched using modern thread and a technique characteristic of commercial production. Poeta said this indicated that there was a “continuum” of production between ceremonial and commercial rather than a simple dichotomy.

She explained: “Some commercial producers may have chosen to make them look more ‘authentic’ than others would have. There was a great deal of time and resources required for ceremonial production, so there was a trade-off when trying to imitate ceremonial features and make an income. It is also statistically certain that there were regional and temporal variation of ceremonial tsantsa production, as it was a long-lasting tradition over a huge geographic region involving many different communities.

“We will only better understand this continuum by scanning more tsantsas ⁠— ideally ceremonial ones with known context and provenience and others known to be of a commercial origin.”

Given limitations of current micro-CT scanners and the huge size of micro-CT scans in gigabytes, the researchers said the ideal strategy was to scan whole tsantsas using clinical CT scanners and specific, diagnostic sections using micro-CT. They noted that DNA analysis could also be used in determining whether tsantsas were made from human remains, although, unlike scans, this requires destructive sampling.

Commenting on the uncertainty around the origins of many tsantsas, Poeta said: “Like many things ‘collected’ in the late 1800s and early 1900s, the context is sadly lacking. There are no original records from the Shuar or Achuar peoples themselves of the process as it was a sacred ceremony. Rather there’s a series of inconsistent and sometimes opposing accounts by missionaries, settlers and explorers.

Lower-resolution clinical CT slice through the Chatham tsantsa

“Through processes of forced colonisation across the Americas, many cultural practices and sacred ceremonies were outlawed, forgotten, changed, or hidden; this is an example of one of those practices. Colonial processes, inconsistent settler narratives, and the mass creation and export of commercial shrunken heads led to where we are now, where it is hard to determine the true origin of the vast majority of tsantsas.”

And referring to the usefulness of the new scanning method, she added: “Ultimately, this project did not have the goal of determining authenticity for the purposes of repatriation, but it would aid those processes later . . . This kind of work is important in determining the specific cultural practices, rituals, and beliefs which resulted in the material remains of a tsantsa. Any decisions about whether a particular tsantsa should be repatriated should lie with the Shuar and Achuar peoples.”

The top image is a 3D-rendering of the micro-CT scan of the Chatham tsantsa by Andrew Nelson, shared under CC-BY 4.0.

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