New Research Offers Fresh Insight into the Iceman’s Death

Ötzi, also known as the Iceman, is showing new signs of life in his gut. Gabriele Andrea Lugli and other researchers from the University of Parma recently published findings on the Iceman in Microbiome Journal. Their research analyzes samples taken from Ötzi’s gut in order to reconstruct and characterize ancient bacteria to provide clues on how bacteria may have affected humans. While some evidence suggests that the Iceman was murdered or died from the lingering effects of an attack, researchers have now uncovered a new possible cause of death: inflammatory bowel disease.

Ötzi was originally found in a receding glacier by two tourists in the Italian Alps in 1991. First thought to be someone from more recent times, research has shown that he lived about 5,300 years ago. Since then, he has become the best known frozen mummy in the world, because his remains are remarkably intact and offer a clear view of the distant past. Though Ötzi’s skin looks like brown caramel and his bones can be seen through his skin, he is very well preserved. Last year, PBS released a documentary titled “Iceman Reborn about artist Gary Staab, who made a replica of the Iceman using 3D printing. One researcher in the film remarked, “He may well be the most studied human being in history.”

Another researcher, referring to new discoveries about Ötzi’s genetic code, noted, “We are rewriting the history of humankind.” It was recently discovered that the Iceman has 61 tattoos, up from a previously smaller number. Ötzi’s tattoos are in locations where there is joint and spinal degradation, indicating the tattoos may have been treatment of some kind. In addition, he was found with a gash on his left hand and an arrow wound in his back, suggesting that he was murdered. He was also found with a copper axe, showing researchers that metalworking was earlier than previously thought.

While climate conditions can alter bacterial communities, low temperatures such as permafrost are optimal for long-term DNA preservation. Using a technique called next generation sequencing, the researchers investigated the human gut microbiota in the soft tissue of the human mummy. The samples yielded an enormous amount of data– about 71 gigabases from 12 biopsy samples.

The Ötztal Alps, where Ötzi was found (source: Creative Commons).

Ancient bacteria, such as the ones found in Ötzi’s gut, can provide clues on the history of diseases, the evolution of bacteria and bacterial infections in humans, allowing scientists to reconstruct pathogens like the plague (Yersinia pestis), leprosy (Mycobacterium leprae) and stomach infections (Helicobacter pylori).

The researchers found that the upper part of the large intestines had ample Pseudomonas species. These bacteria are typically found in the soil. The presence of P. fluorescens in Ötzi’s intestines suggests that his immune system may have been compromised and that he may have been ill with inflammatory bowel disease at the time of his death.

Other findings included the fact that even though modern P. veronii have been isolated from water springs, the ancient strain seems to have the ability to colonize the human gut. The bacteria also shares genetic material with Pseudomonas strains in isolated parts of Antarctica, a fact which supports its ancient origin. Evidence suggests that the evolution of the bacteria was helped by the development of its virulence.

Tattoos found on the Iceman (source: Creative Commons).

The biopsy also revealed the ancient genome of C. perfringens in the Iceman’s gut. It shares the same genetic branch as another species, well-known as a cause of food poisoning. This finding suggests that C. perfringens was a cause of food poisoning in humans during Ötzi’s time. The researchers believe they may have also found a species of Clostridium incapable of metabolizing sucrose.

The scientists analyzed the samples at the Ancient DNA Laboratory of the EURAC-Institute for Mummies and the Iceman in Bolzano, Italy. Scientists had to follow stringent guidelines in order to work with the samples, including wearing protective clothing, exposing the equipment to UV-light, sterilizing surfaces with bleach, and using filtered pipette tips. These procedures protected Ötzi against contamination and the researchers against infection.

Flyer from the Otzi-Museum (source: Creative Commons).
Flyer from the Otzi-Museum (source: Creative Commons).

There is still a great deal of research that can be done on the biopsied samples in order to provide more clues on the cause of the Iceman’s death. Future explorations may also reveal more information on the interactions of bacteria and humans thousands of years ago. More than two decades after its discovery, the 5,300 year old mummy continues to yield new discoveries.

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