“How in God’s Name Is Anything Living up There?” – Discovery of Mice Mummies on 20,000-Foot Volcanoes Baffles Scientists

The study dismisses any connection to Incan rituals, suggesting that mice ascended independently.

In the midst of the driest desert on Earth, atop 20,000-foot volcanoes, the environment was harsh and unforgiving. The temperatures remained perpetually below freezing, the oxygen levels were less than half of what is found at sea level, and the peaks were battered by gale-force winds that swept across the sparse, rocky terrain.

So when archaeologists first reported stumbling across a few mouse cadavers during expeditions to several Andean peaks in the 1970s and ’80s, they figured, naturally, that the rodents must have hitched a ride with the Incas who once pilgrimaged a thousand-plus miles to what they considered sacred sites.

Those apexes served as altars for Capacocha, the ritual sacrifice of children to several Incan gods. Maybe, the thinking went, the mice had scurried into firewood or other supplies hauled up the slopes by the Incas. Or they were among the animal sacrifices that sometimes accompanied the humans.

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

A New Hypothesis Emerges

But Storz would inadvertently cast doubt on the hypothesis in early 2020. Alongside friend and fellow mountaineer Mario Pérez Mamani, he captured a live specimen of leaf-eared mouse atop the 22,000-foot peak of Llullaillaco (zhoo-zhuh-ZHEYE’-koh), a volcano straddling the Chile-Argentina border. No mammal had ever been found living at such extreme altitude.

Alongside the capture of more live specimens, Storz and his colleagues have now reported the discovery of 13 leaf-eared mouse cadavers across the summits of three neighboring volcanoes — Salín, Púlar, and Copiapó — that each stretch nearly 4 miles above sea level.

“These are basically freeze-dried, mummified mice,” Storz said.

Jay Storz, a professor of biological sciences at the University of Nebraska–Lincoln, works to excavate a mouse mummy on the summit of an Andean volcano. Analyses of 13 mummified cadavers, combined with the capture of live specimens, suggest that the rodents scaled the Mars-like peaks on their own — and are somehow managing to live on them. Credit: Mario Pérez Mamani

Analyzing the baker’s dozen of mummies has only reinforced the team’s conviction that the seemingly modest mice ascended the volcanoes without Incan assistance. By measuring concentrations of carbon-14, an atomAn atom is the smallest component of an element. It is made up of protons and neutrons within the nucleus, and electrons circling the nucleus.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>atom that decays at a known rate, the team determined that the eight mummies atop Salín and one on Copiapó died no more than a few decades ago, likely after 1955. The four mummies on Púlar perished, at most, 350 years ago — a full century after the last of the Incan empire fell to Spanish invaders.

“It now seems more and more clear,” Storz said, “that the mice got there of their own accord.”

Genetic Insights and Baffling Survival

The mummified state of the mice also helped preserve their DNADNA, or deoxyribonucleic acid, is a molecule composed of two long strands of nucleotides that coil around each other to form a double helix. It is the hereditary material in humans and almost all other organisms that carries genetic instructions for development, functioning, growth, and reproduction. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA or mtDNA).” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>DNA, allowing Storz’s collaborators from the University of Montana to compare genetic variation among leaf-eared mice collected in the lowlands, midlands, and highlands of Atacama Desert. Analyzing that variation across members of a speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>species can help trace the evolutionary history of populations separated by distance, barriers or, in this case, altitude.

Storz and his colleagues wondered whether the genomes of the skyscraping, mummified mice might represent a distinct subpopulation of the leaf-eared rodent — one with a colonization history different from that of their lower-dwelling peers.

“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,” Storz said, citing it as more evidence that the mummies were not hitchhikers but mountaineers.

In fact, the team found that two pairs of the leaf-eared mummies on Salín were closely related, possibly siblings or parents and offspring. And it noted another telltale: the equal ratio of males to females among the mummies. Combined with the recent discovery of other live specimens and mouse burrows in the heights of the Puna de Atacama, or Atacama Plateau, Storz said it seems that the leaf-eared mouse is not just touring the volcanic summits, but somehow living on them.

“It’s exactly what you’d expect,” he said, “if you were to capture a set of mice from some localized area in an environment that’s habitable.”

Unanswered Questions and Ongoing Research

Which is bewildering, Storz said, given that the Puna de Atacama ranks among the most inhospitable locales on the planet — one so arid, cold, and oxygen-poor that NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>NASA has visited the Atacama to practice searching for life on MarsMars is the second smallest planet in our solar system and the fourth planet from the sun. It is a dusty, cold, desert world with a very thin atmosphere. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Mars.

“Even at the base of the volcanoes, the mice are living in an extreme, Martian environment,” he said. “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?”

It’s one of a few questions that the researchers are continuing to pursue. Members of Storz’s lab and colleagues in Santiago, Chile, have since established colonies of leaf-eared mice collected from various altitudes. By acclimating each group to conditions that simulate the Puna de Atacama at 20,000 feet, the researchers hope to pinpoint whatever physiological adaptations are helping the rodents cope.

Even more fundamental is the question of what would drive the mice to such heights in the first place. Like most small rodents, the leaf-eared mouse — which grows to about 2 ounces — spends a fair amount of its time, energy, and attention avoiding predators. And even in the Puna de Atacama, those predators are numerous: foxes, mountain lions, smaller cats, birds of prey.

Could the dangers imposed by the Atacama summits — the near-absence of water, the seeming lack of food, the threat of freezing to death — really be worth the promise of escaping predation all together?

“Certainly, if you’re hunkering down on top of a 6,000-meter volcano, you’re at least safe from that,” Storz said. “You just have other things to worry about.

“But why they’re ascending to these extreme elevations is still a mystery.”

Reference: “Genomic insights into the mystery of mouse mummies on the summits of Atacama volcanoes” by Jay F. Storz, Schuyler Liphardt, Marcial Quiroga-Carmona, Naim M. Bautista, Juan C. Opazo, Timothy B. Wheeler, Guillermo D’Elía and Jeffrey M. Good, 23 October 2023, Current BiologyCurrent Biology is a peer-reviewed scientific journal published biweekly by Cell Press. It is focused on all aspects of biology, from molecular biology and genetics to ecology and evolutionary biology. The journal covers a wide range of topics, including cellular biology, neuroscience, animal behavior, plant biology, and more. Current Biology is known for its high-impact research articles, as well as its insightful commentary, analysis, and reviews of the latest developments in the field. It is widely read by scientists and researchers in biology and related fields, and has a reputation for publishing groundbreaking research that advances our understanding of the natural world.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Current Biology.
DOI: 10.1016/j.cub.2023.08.081

This work was funded by grants from the National Institutes of Health
The National Institutes of Health (NIH) is the primary agency of the United States government responsible for biomedical and public health research. Founded in 1887, it is a part of the U.S. Department of Health and Human Services. The NIH conducts its own scientific research through its Intramural Research Program (IRP) and provides major biomedical research funding to non-NIH research facilities through its Extramural Research Program. With 27 different institutes and centers under its umbrella, the NIH covers a broad spectrum of health-related research, including specific diseases, population health, clinical research, and fundamental biological processes. Its mission is to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce illness and disability.
” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>National Institutes of Health, the National Science Foundation, the Geographic Society, and FONDECYT.

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