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Mummified mice lived in Mars-like conditions in the Andes mountains

In a surprising discovery, mummified remains of mice have been found on the summits of 20,000-foot volcanoes in the Andes mountains. The revelation raises new questions about the remarkable survival instincts of these small rodents.

Hostile environment 

The initial findings date back to expeditions in the 1970s and ’80s when archaeologists reported stumbling upon mouse cadavers atop towering Andean volcanoes.

These peaks, situated in the driest desert on Earth, present a hostile environment with freezing temperatures, low oxygen levels, and punishing gale-force winds. 

Sacred pilgrimages 

Given the daunting surroundings, researchers initially believed that these rodents might have been transported to such heights by the Incas, who considered these summits sacred and often made pilgrimages spanning over a thousand miles. 

The peaks served as altars for Capacocha, a ritual wherein children were sacrificed to various Incan gods. It was theorized that mice might have accidentally found their way amidst the supplies or were deliberately brought as part of the animal sacrifices.

“You can’t fault the archaeologists for thinking this way, because what other explanation is there? Nothing could be living up there, so they had to have been brought there,” said Professor Jay Storz of the University of Nebraska–Lincoln.

Astounding discoveries

However, Storz and his team inadvertently challenged this narrative in early 2020 when they captured a live leaf-eared mouse at an astounding altitude of 22,000 feet on Llullaillaco, a volcano on the Chile-Argentina boundary. This marked the first-ever instance of a mammal being discovered alive at such an altitude.

Furthermore, the team reported discovering 13 more mummified leaf-eared mice on the summits of nearby volcanoes – Salín, Púlar, and Copiapó. 

Further analyses 

Through carbon-14 analysis, the experts determined that most of these mummies were relatively recent, with some dating post-1955. This contradicted the earlier belief that these mice were brought by the Incas, especially since the Incas had fallen to Spanish invaders centuries before the mummies’ dated time.

Compelling genetic evidence further validated the mice’s natural presence at these heights. DNA analysis by collaborators from the University of Montana revealed that the genetic variation of these high-altitude mice was consistent with those found in the lower regions of the Atacama Desert.

Skilled mountaineers 

“Our genomic data indicate no: that the mice from the summits, and those from the flanks or the base of the volcanoes in the surrounding desert terrain, are all one big happy family,” said Storz. He said it was more evidence that the mummies were not hitchhikers but mountaineers.

Intriguingly, observations also reveal an equal gender ratio among the mummies and evidence of local mouse burrows. This suggests that these rodents have not only ventured to these heights but are also sustaining a life high up on the volcanoes.

Mice lived in extreme mountains

The Puna de Atacama, where these mice reside, is so extreme that it has served as a practice ground for NASA’s Mars missions. 

“Even at the base of the volcanoes, the mice are living in an extreme, Martian environment,” said Storz. “And then, on the summits of the volcanoes, it’s even more so. It feels like outer space.

“It just boggles the mind that any kind of animal, let alone a warm-blooded mammal, could be surviving and functioning in that environment. When you experience it all firsthand, it even further impresses upon you: How in God’s name is anything living up there?”

Yet, many questions remain. While the high altitudes offer refuge from predators like foxes, mountain lions, and birds of prey, what drives these mice to endure the harsh conditions of these summits remains a mystery.

Image Credit: Jay Storz, University of Nebraska–Lincoln

The research is published in the journal Current Biology.

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