Researchers have uncovered traces of ancient microbes inside a mummy - unexpected "signs of life" that may have persisted for more than 5,300 years.
The study, recently published in the journal Microbiome, centers on Ötzi the Iceman, a mummy found by a tourist inside a glacier in the Alps in 1991, news agency SWNS reported.
Ötzi's remains date back to 3300 B.C., before Stonehenge and the Egyptian pyramids were built. He was between 25 and 35 years old when he died, and stood roughly 5 feet 2 inches tall.
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Researchers originally believed he succumbed to exposure or exhaustion while crossing the Alps, though later examinations found that an arrowhead was lodged in his left shoulder - suggesting he likely bled to death.
Experts at Eurac Research found that Ötzi's remains still contain a complex community of ancient and modern microorganisms - offering a rare glimpse into the microbial past of early humans.
While studying the mummy at the South Tyrol Museum of Archaeology in Bolzano, Italy, researchers found cold-adapted yeasts and genetic traces of bacteria from Ötzi's ancient gut microbiome.
They also differentiated between microorganisms that were present during Ötzi's lifetime and those that colonized his body after his death, using tissue samples, swabs and genetic analysis.
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The team analyzed ice from the surface of Ötzi's body, as well as meltwater inside the mummy. Researchers also drew on intestinal tissue and stomach-content data from previous studies.
A surprising discovery was the presence of cold-adapted yeast species, likely originating from the glacial environment, which have persisted on Ötzi's body to the present day.
Ötzi's microbiome is also unique in that it contains gut bacteria that aren't typically found in the intestines of modern humans, researchers said.
"Ötzi therefore offers a rare glimpse into humanity's microbial past," Eurac Research noted in a statement.
Some of the microbes may still exist in a dormant state more than 5,000 years after Ötzi's death, as his body sits at the South Tyrol Museum, the experts said.
Elisabeth Vallazza, director of the South Tyrol Museum of Archaeology, described the mummy's preservation condition as "very stable today."
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"Close microbiological monitoring ensures that the mummy suffers no damage," said Vallazza in a statement.
"But further research and full conservation efforts are certainly needed to preserve it for many more generations."
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Despite the findings, there is still mystery surrounding how microorganisms survive and interact within Ötzi's frozen remains.
The conditions "are not yet fully understood," said conservation expert and co-author Marco Samadelli, as SWNS reported.
"This study expands our knowledge in this area."
Frank Maixner, director of the Institute for Mummy Studies at Eurac Research, said the discovery points to a continuous presence of certain microorganisms on the mummy throughout its long history.
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"These yeasts have accompanied Ötzi on his long journey through the millennia," Maixner said in a statement.
Ötzi is "not a static relic, but a dynamic biological system," he added.
The latest findings add to a growing body of recent research on mummies and other ancient remains.
Earlier this spring, officials announced that researchers from the University of Barcelona discovered a copy of Homer's "Iliad" placed on top of a mummy in Egypt.
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Last year, utility workers in Lima, Peru, uncovered a millennia-old mummy while on the job.
