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Friday, February 23, 2024

Ever Seen Inside a Mummified Cat? Well Now You Have

Thousands of years ago in ancient Egypt, a cat, a bird, and a snake met ceremonious yet unfortunate ends. Sacrificed for the benefit of humans venturing into the afterlife, the animals were preserved and wrapped, forever logged into the historical record as mummies. And now, scientists are peering through their delicate bandages—the snake wrapped up in an oval, the cat having snapped at the neck at some point in the past few millennia, the bird still taking a fairly birdlike shape—to show the animals in stunning detail.

Writing today in the journal Scientific Reports, a multidisciplinary team of researchers in the UK describe how they used microCT technology—think of it like the computerized tomography (aka CT) scan you’d get in a hospital, only with a way higher resolution—to uncover new details about how the critters lived and died. Spoiler alert: You do not want to be a sacrificial animal.

When you lie down in a CT scanner, an x-ray emitter rotates around you, shooting beams through your body. A collector opposite the emitter gathers these x-rays, creating a 2D snapshot of your body with each rotation. After many rotations, the technician combines these 2D images all together to create a 3D representation of your insides. “But then there's a resolution limit to that technology,” says Swansea University materials scientist Rich Johnston, lead author on the new paper.

Because we’re working in 3D here, resolution is measured as a three-dimensional voxel, the counterpart to the two-dimensional pixel. Medical scanners go down to around a 100-micron (a millionth of a meter) voxel size, and that works just fine for humans—our morphology is much bigger than a cat’s or snake’s or bird’s. But to get a good look inside these tiny mummies, Johnston and his colleagues needed to bump up the resolution. “You can't really make out features, you can't do accurate measurements” at human-scale resolution, Johnston says. “You just won't see the types of things that we were able to determine—causes of death, or what the last stages of an animal's life might have been like, how it was kept.”

The solution was microCT, which allowed these researchers to get down to around 20 microns. Unlike a human CT scan, this device doesn’t rotate around a stationary subject—it’s got a fixed x-ray emitter and detector, and the technician can move the object around within the device. “The main difference is we can move the sample closer to the source of the x-rays, which increases the resolution,” says Johnston.

The result of his imaging of the mummies is a detailed 3D representation of the skeletal remains of animals that human eyes haven’t seen for thousands of years. Like, really detailed: Each scan was about 5 gigabytes of data. The researchers could even see desiccated tissues and organs, like lungs, in the images. And with special VR software, Johnston could get right up close to all that anatomy. “This was useful for working out the placement of the limbs and tail in the cat, assessing damage of the skulls, and imagining directionality of any damaging force,” he says. “For specific measurements, using VR allowed me to get ‘inside’ the lower mandible of the cat mummy and effectively perform accurate digital calliper measurements for age determination.”

The team also used the data to 3D-print the cat’s skull at two and a half times its actual size, allowing them to effectively hold the specimen in their hands without ever opening up the mummy’s bandages.

What they found was unsettling. By analyzing the animal’s morphology, they determined that it had likely been a domestic cat, as opposed to a wildcat, swamp cat, or sand cat, which the Egyptians might have gathered from their surroundings. By examining the skull, coauthor Richard Thomas of the University of Leicester could determine which fractures happened in “wet,” or living, bone, and which had happened in “dry,” or dead, bone. Based on fracture patterns, damage to the cat’s mandibles likely happened at the time of death, while large-scale damage to the left side of the cranium happened sometime in the thousands of years after the animal had been mummified.

The team also looked at damage to the cat’s vertebrae to determine its likely cause of death. “We identified that there's a clear misalignment between the vertebrae,” says Johnston. “And that potentially could be strangulation, which has been documented as part of the process for producing animal mummies. Animals were reared in their millions and killed to create these artifacts.”

Things got even more disturbing when Johnston took a closer look at the animal’s jawbones. “There were unerupted teeth that really helped us nail down the age and showed that this cat was in fact a kitten,” says Johnston. “Really young—those teeth hadn't come through yet. They were just waiting within the jaw.”

OK, sorry about all that ancient brutality, but I’m happy to report that at least there’s no evidence that the bird died of strangulation. Johnston and his colleagues identify it as likely being a kestrel, a kind of falcon, the most commonly mummified raptor from ancient Egypt. This one had suffered extensive damage to its beak and was missing the foot on its left leg, though this probably happened after mummification, as the limb was protruding from the wrapping.

The snake fared no better than the cat, though at least its sacrifice would have been a bit quicker. Based on its morphology, the researchers reckon it was a cobra, also a baby at the time of death. And they also found clues as to its cause of death in its separated vertebrae: One way to kill a snake is to pick it up by the tail and either swing its skull into the ground, or swing it above your head to destroy the spine. “It's identified as a common bull-whipping method, where you dislocate the vertebra along its body, and effectively that kills it,” says Johnston.

The researchers uncovered more evidence that the snake was likely suffering even before it was executed: Its kidneys had hardened before death, probably from dehydration. “You find that actually snakes in captivity that are deprived of water tend to have calcification of the kidneys,” says Johnston. “And so that, all of a sudden, is starting to tell us not just about this snake that's in the packaging, but how it was kept when it was alive prior to its death and prior to mummification. And you start to build a picture up of that time.”

That picture is quite macabre. Historians reckon that the ancient Egyptians mummified perhaps 70 million animals. They likely bred many of them, like the kitten; the cobra showing symptoms of dehydration is perhaps a consequence of it being kept in captivity. Some of these animal mummies were meant to accompany their human counterparts into the afterlife as a source of food. Others were votive offerings for the gods: Raptors like the kestrel were associated with solar deities, while cats were associated with Bastet, the goddess of fertility and domesticity.

Snakes were hugely important to the ancient Egyptians, according Alexander Nagel, who works with the ancient Egypt collections at the Smithsonian Institution’s National Museum of Natural History, but wasn’t involved in this new study. “We know that serpents were considered the sacred animal of quite a good number of ancient Egyptian deities,” Nagel says. This knowledge is all gleaned easily enough from period records jotted down on papyri. “What we have not learned from papyri is how animals were prepared before they were dedicated to a deity. Studies like these help us to obtain a wealth of information on the ancient Egyptian environment, religion, veterinary practices, mummification technology, trade, and culture,” he continues.

With microCT, researchers can obtain all this information noninvasively, so when scanning technology gets even better, they’ll have perfectly intact specimens to revisit once more. “This paper pushed resolution and analysis to its limits, revealing more than could be determined through lower-resolution methods or even through real-life unwrapping,” says Johnston. “New understanding can contribute to building the picture of life at that time, while the specimens remain undamaged.”

And that, my friends, is a wrap.

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