Ötzi the Iceman is about as deceased as an organism can be.
He died 5,300 years ago, his body exquisitely mummified in Italy's glacial Ötztal Alps – one of the oldest and best-preserved human mummies ever discovered.
In the extreme cold of the alpine environment in which he died, microbial activity was suppressed – and, since microbes are the main driver of decomposition, Ötzi did not succumb to its ravages.
But the Iceman's corpse may not have been completely devoid of life.
A new study of the microbes all over his body suggests that some potentially active species may be nearly as old as the mummy himself – while others may have adapted to the conditions of the cold storage where he lies today.
"A mummy's microbiome is unique because we are dealing with microbes that are over 5,000 years old and, at the same time, with modern microbes that have been introduced since the discovery," says first author Mohamed Sarhan, a microbiologist at Eurac Research in Italy.
Ötzi (pronounced like 'curtsy' without the 'c') was discovered in 1991, when two hikers spotted what they thought was a recently deceased mountaineer protruding from the melting ice of a glacier, at an elevation of 3,210 meters (10,530 feet).
It was only once his body had been transported to a laboratory that scientists understood the true significance of the find – a Copper Age hunter who had lived and died around 3300 BCE, mummified so exceptionally well that he appeared far more recent.
Since then, scientists have discovered much about Ötzi.
He was around 46 years old when he died, was adorned with at least 61 hand-poked tattoos on his dark skin, wore clothing stitched from the skins of multiple animals, and ate a last meal rich in ibex fat, wild meat, and cereals.
Previous studies even examined his gut microbiome, finding it more consistent with that of ancient, non-industrialized human populations than with that of modern Western populations.
Researchers also recovered an ancient strain of Helicobacter pylori, the stomach bacterium associated today with ulcers and gastric cancer.
However, all these studies had one thing in common: They mostly treated those microbes as biological remains, rather than investigating whether any might still be active today.
And no one had undertaken the painstaking work of extricating Ötzi's native microbiome from environmental contaminants that may have moved in after he died, both on the glacier and afterward, when he was moved to cold storage to prevent decomposition.
Sarhan and his colleagues took swab samples from all over Ötzi's body, as well as meltwater inside him. They also used data on intestinal and stomach tissue from previous studies, and tested a sample of the soil from where he was found, collected at the same time as the Iceman himself.
They ran these samples through DNA and RNA sequencing, looking for patterns in the types of microbes therein.
Broadly, the microbes fell into two main groups. The first were ancient microbes that were part of Ötzi's living microbiome.
The second were cold-loving yeasts found on Ötzi's skin and in meltwater collected from inside the mummy. These yeasts were highly specialized species adapted to cold environments, genetically related to microbes found in gelid regions such as Antarctica.
This suggests that these microbes likely originated in the glacier environment that preserved Ötzi's body.
But there was something else a bit strange. Some of the samples were heavily degraded, showing that the microbes were ancient – but others were relatively fresh, implying ongoing activity.
"We see continuity here," says microbiologist Frank Maixner, director of the Institute for Mummy Studies at Eurac Research.
"These yeasts have accompanied Ötzi on his long journey through the millennia."
There's another piece of the strange puzzle. Some of the microbes may have benefited from the conservation techniques used on the body.
After he was found, Ötzi's body was treated with phenol, a toxic compound that prevents fungal growth. Three of the four yeasts were species capable of metabolizing phenol.
It is, to be clear, impossible to tell whether these active microbes are the descendants of a long, unbroken line quietly making their home on Ötzi's body for millennia, even in the ice-cold, or whether they were dormant and revived after the mummy was thawed.
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But the evidence strongly indicates that, in some fashion, the Iceman's body supported their survival.
Samples taken in 2010 and 2019 showed that one cold-loving species increased over the decade – suggesting that at least some of the microbes are surviving and even slowly reproducing in the subzero conditions of Ötzi's storage chamber.
"The Iceman mummy is not a static artifact but a dynamic ecosystem of living archive where ancient glacier-derived microbes and modern contaminants coexist under museum conditions," the researchers write.
The findings have been published in Microbiome.