Mummies are well-preserved bodies that have been frozen (sometimes literally) in time. By studying these remnants of the past, we learn about ancient cultures - and bizarre death rituals from history. But how do you get answers out of a mummy? That's a science unto itself.
Though the mummies of Egypt are by far the most well known, they are certainly not the only ones that exist. In fact, archaeologists and others have discovered mummies throughout the world, including in countries such as Chile, Greenland, Italy, Iran and China.
Mummies differ from your run-of-the-mill skeleton or dead body, in that the deceased's tissues have been preserved over centuries or even millennia. People have used various techniques to create mummies - but mummies also commonly form from prolonged exposure to a desiccating environment, such as a frigid mountaintop, an oxygen-deprived bog or a dry, hot desert.
In the past, studying mummies was a destructive endeavor - scientists would unwrap Egyptian mummies, or dissect other mummies to take a look at internal organs (or what was left of them). But nowadays, numerous non-invasive techniques can be employed to study mummies. For the sake of this discussion, we'll focus on these modern, safer methods.
Radiology
In 1895, physicist William Roentgen discovered X-rays while working with a cathode ray tube in his lab. A year later, in 1896, scientists applied the new technology to a group of mummies, and X-ray imaging became the first non-destructive technique to study these ancient, well-preserved bodies, according to Emory University's Michael C. Carlos Museum. Within a couple decades, X-ray imaging became the go-to method to study mummies, because it allowed people to peer beneath Egyptian mummies' wrappings, without having to actually unwrap them.
X-ray images can reveal not only what artifacts may be sealed within their wraps or clothing (information that can help tease out how important the mummified person was in life), but also what kinds of health problems the person may have had, including diseases, dental issues, fractures and traumatic wounds.
For example, in 1928, the Field Museum X-ray photographed the mummy of a 7th century B.C. Egyptian boy - based on the irregular development of some of his bones, the researchers surmised that the kid had a calcium deficiency and was malnourished. More recently, scientists used X-ray images to study several dozens of Egyptian mummies found in Italian museums, and discovered that a majority of the specimens suffered from joint diseases and dental problems, such as tooth wear and tooth loss, while they were alive.
In the 1970s, scientists began complementing their X-ray imaging techniques using computed tomography (CT) scans - which provide a cross-sectional image of a body by combining multiple X-ray images taken from various angles. The scans are able to provide a much clearer internal picture than basic X-rays, allowing scientists to make new discoveries about mummies at a maddening rate.
A few years ago, researchers reviewed studies on Egyptian mummies since the advent of CT scans. The results further suggested that dental issues, including periodontal diseases, abscesses and cavities, plagued ancient Egyptians; the meta-analysis also showed evidence of numerous other health issues, such as bone disorders, infections and traumas.
CT scans of mummies have revealed a number of other interesting finds: coronary arteriosclerotic disease has been around in China for over two millennia; Ötzi the Iceman suffered a fatal blow to the head; ancient Egyptians suffered from atherosclerosis (which is typically considered a modern disease attributed to a sedentary lifestyle); and the 13-year-old Incan "Maiden" had food in her system and had not defecated shortly before her ritual death, suggesting she was not in a state of distress.
Within the last decade, scientists have begun using MRI machines on mummies. The technique can typically only be used on hydrated tissues, but that limitation apparently is not a deal-breaker. Last year, researchers examined a dry Egyptian mummy using a newly developed technique for MRI scans and found evidence of the rare Hand-Schueller-Christian's disease.
Mass Spectrometry
Mass spectrometry is a common chemical analysis technique that scientists can use to sort out different types of atoms and molecules in a sample. Archaeologists have utilized mass spectrometry for decades to study mummies - the technique tells them the specific molecules, and their respective concentration, that are present in tissue, clothing and other samples.
Mass spectrometry yields particularly useful information when applied to hair samples. Reason being: Hair provides a record of what substances, including narcotics and other drugs, are swimming in the blood stream when new hair cells form. Back in 1991, for instance, researchers found that benzoylecognine, a metabolite of cocaine, can be reliably detected in the hair of mummies - a finding that's still used in research today.
In a study published in the journal PNAS this week, researchers analyzed the hair samples of three famous Incan child mummies - the Maiden (image above), Llullaillaco Boy and Lightning Girl - for cocaine, benzoylecgonine and the chemical cocaethylene, which the liver produces when cocaine and ethanol are both in the blood. Knowing that hair grows at a relatively constant rate, they were able to create a timeline showing the levels of coca (from which cocaine is derived) and alcohol that the children consumed in the months leading up to their deaths.
And in a previous study, the same team of researchers revealed the child mummies' final diets by analyzing hair samples (using mass spectrometry) for different isotopes of carbon, hydrogen, oxygen and nitrogen. The results showed that the children ditched their previous diet of potatoes and began to eat "elite" food, including dried llama meat and maize, after they were selected to take part in the sacrificial ritual that ultimately killed them.
Of course, mass spectrometry has been used to study other mummies, too. Recently, scientists found nicotine traces in the hair of Chilean mummies dating between 100 B.C. and A.D. 1450. Contrary to previous beliefs, the results showed that people in the area (San Pedro de Atacama) consumed nicotine for over a millennium and on a society-wide basis. In another study, researchers used the technique to analyze the resin on the wrappings of Egyptian mummies.
Scientists have even used mass spectrometry to analyze the clothing of the very well studied Iceman Ötzi to figure out what animals his skins came from. The study showed his moccasins were made of cattle, while his coat and pants were made of sheepskin. You may wonder why the researchers didn't just do a DNA analysis on the skins, but they explain that the hides would have gone through multiple manufacturing processes that would likely have destroyed the DNA - the proteins used in the mass spectrometer, however, are more resilient.
DNA Analysis
Analyzing the DNA of a mummy can potentially provide a wealth of information about it, including its sex, familial relations and diseases it may have had in life. The use of DNA analysis on ancient mummies stems back to 1985, when a PhD student claimed to have cloned nuclear DNA from a 2,400-year-old Egyptian mummy. Since then, scientists have published countless papers on the analyses of different mummy DNA, which they were able to do by first amplifying fragments of DNA using a technique called polymerase chain reaction (PCR).
In 2002, researchers used the technique to determine what Ötzi's last meals were. Other scientists used DNA analysis and PCR to discover that Egyptians had to deal with leishmaniasis (a parasite-borne disease that causes painful sores and death), which suggests an origin for the modern disease. And perhaps most famously, researchers carried out DNA tests on King Tut and other royal mummies a few years ago, yielding a number of interesting results, including that malaria is the most likely culprit in the Pharaoh's demise.
Though DNA analysis is used time and again on mummies, the method is not without controversy. Scientists take issue with the facts that ancient DNA is easily damaged, degrades quickly in warm climates and is easily contaminated by modern DNA (which is made all the worse when PCR is involved), suggesting there may be problems with many of the finds made over the years - especially those of Egyptian mummies.
A few months ago, a group of scientists unveiled a potential resolution to the contamination problem: The next generation of DNA sequencing (NGS). The Scientist explains:
NGS enables a metagenomic approach, meaning that, prior to sequencing, researchers amplify all DNA fragments in a sample, including small bits of ancient DNA that were missed by traditional methods. This provides a broad snapshot of the sample's genetic material and offers a more accurate reading of the true ratio of ancient DNA to modern DNA. "Contaminants are still a tiny fraction, because you're looking at the whole pool," says [geneticist Tom Gilbert of the Center for GeoGenetics in Denmark]. The speed of next-gen platforms also means researchers can sequence a sample over and over again, which makes it easier to check for patterns of damage that distinguish ancient DNA from modern DNA.
And more
Given that DNA analysis may not be the best tool to learn about the diseases and health issues that ancient mummies had in life, scientists have come up with another approach: Protein analysis. In a study published last year, scientists used a technique called shotgun proteomics to study the Incan children discussed previously, and discovered that the Maiden had a lung infection before she died. I explained the technique in LiveScience:
The researchers used a technique called shotgun proteomics. They placed their samples into a device called a mass spectrometer, which broke all of the sample's proteins into their constituent parts, amino-acid chains. Sophisticated software compared these parts with existing proteins of the human genome to determine the actual proteins in the samples, [lead researcher Angelique Corthals] explained. "You couldn't use this technique for an organism that we don't have the complete genome for," she said.
More recently, scientists analyzed the proteins of our famous friend, Ötzi. The study supported the previous finding that the Iceman received a hard knock on the head.
Proteomics is not the only other technique archaeologists use to study mummies. Though not employed as readily as in the past, scientists sometimes use endoscopy (the study of the internal body using a flexible tube), histology (microscopic study of tissues), and immunocytochemistry (a method to look for antigens associated with particular parasites).
Astonishingly, researchers are even using 3-D CT scans to reconstruct mummies' faces, allowing us to finally see what these mummies looked like when they were alive.
Top image via U.S. Navy. Inset images via University of Zurich, Johan Reinhard, American Journal of Roentgenology.
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