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Scientists have discovered how mice survive at extreme altitudes on the tips of icy dormant volcanoes in the Andes.

The area where the mice call home extends more than 1 mile (1.6 kilometers) above the world's highest human settlement . The air is thin, temperatures are blisteringly cold, and a desert ecosystem ensures water and vegetation are extremely scarce.

"As a mountain climber standing on the summit of these peaks, the idea that there could be animals living in these barren godforsaken environments is just really mind-boggling," Jay Storz , a professor of biological sciences at the University of Nebraska–Lincoln, told Live Science.

In 2020, Storz led a team of mountaineering scientists who recorded Andean leaf-eared mice ( Phyllotis vaccarum ) at a record-breaking altitude of 22,110 feet (6,739 meters). The mice were living on the summit of Llullaillaco , the world's highest historically active — now dormant — volcano, located on the border between Argentina and Chile.

Now, in a new study published July 9 in the journal Science , Storz and his colleagues have revealed the biological mechanisms behind the mice's extreme survival. It turns out that the species has evolved a variety of adaptations to survive at such high altitudes, including the ability to eat plants that would normally be toxic.

Before the discovery of the high-altitude mice, researchers had assumed that mammals could only survive up to around 18,000 feet (5,500 m) above sea level. But these hardy animals smashed that record, while also thriving at lower altitudes.

"One of the really notable things about this particular species is that it has such a broad elevational range, from sea level along the desert coastline of northern Chile, all the way up to the summits of some of the highest peaks in the Andes," Storz said.

To better understand these remarkable mice, the researchers studied members of the species at low, middle and high altitudes between 2020 and 2023. The work mixed mountain climbing and animal surveying techniques, with Storz and his team ascending the mountains and setting traps to catch and record the mice.

Storz said that a well-acclimatized mountain climber can tolerate these high elevations for a very short period, but that the conditions are "not remotely compatible with long-term human survival."

The expeditions can be dangerous even for experienced climbers: one of Storz's colleagues was evacuated during a separate expedition in Peru after they developed high-altitude pulmonary edema — a life-threatening form of altitude sickness that causes fluid to build up in a climber's lungs.

Storz surveyed the mice with other experienced mountain climbers. Here he is pictured with Mario Pérez Mamani and Franz Checca on the summit of Hualca Hualca in Peru. (Image credit: Jay Storz) The researchers sent some of their specimens to labs in Chile for further analysis. This included putting the mice into small chambers and measuring how they adapted to extreme cold and oxygen deprivation. The team also sequenced the Andean leaf-eared mouse genome, which revealed a variety of local adaptations to different altitudes. For example, the mice living at high elevations were better at maintaining their body heat and oxygen levels than those taken from lower altitudes, according to a statement released by the University of Nebraska-Lincoln .

Another change in the high-altitude mice's genes enabled them to digest food and detoxify plants that would otherwise be harmful to them, according to a statement released by McMaster University in Canada. This special adaptation helps the mice get enough food on the sparsely vegetated volcanoes.

The researchers also revealed that the high-altitude mice were much more active in the daytime, perhaps due to a lack of predators and warmer temperatures during those hours. However, despite local adaptations, the mice were still extremely similar genetically across their elevation range. All of the mouse populations overlapped, which prevented high-altitude individuals from becoming isolated or especially distinct from their low-altitude kin.

Not all of the mice survived the researchers' study. To fully understand the biology of the mice, researchers needed to euthanize them and study their tissues. They also wanted to preserve "voucher" specimens to act as permanent representatives of the species in museums, which researchers can keep returning to for further study. According to the study, the team collected 167 of these voucher specimens.

Storz noted that it's very valuable to have a biological record of specimens archived in museum collections for future generations. He added that their work was not having any impact on the viability of the mice populations, and that the animals were killed humanely, although he did not disclose any details.

"King of the mountains"

Study co-author Graham Scott , a professor of biology at McMaster University in Canada, said that the take-home message of the new research was how life can overcome such extreme environments, and not just survive but thrive. In this case, the mice did this by developing solutions for the cold, oxygen deprivation and food scarcity.

"It just shows the complex ways that evolution has made these animals the king of the mountains," Scott said.

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Enduring harsh conditions high in the Andes likely comes with some benefits. Scott said that competition is probably the biggest reason for the mice living at such high elevations. The mice are also pretty much left to their own devices, and thus likely have less to fear from predators.

But this begs the question: Are there any animals living higher than the mice?

"Birds are always a bit hard to nail down because, of course, they can fly and there's certainly records of birds flying at higher elevations than that," Scott said. "But we think this is probably the highest-dwelling animal."

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The face of a young woman crowned with a laurel wreath, buried in elaborate clothing and unusual cork sandals, has appeared nearly 1,700 years after her death.

She is one of 16 people from Aquincum, a Roman-era city in present-day Hungary, whose faces have been reconstructed for "Once We Were Like You," a new exhibition at the Aquincum Museum in Budapest. The display pairs skulls excavated in and around the ancient city with scientifically informed approximations of how their owners may have looked in life.

Six of the reconstructions are hyperrealistic silicone models, complete with artificial eyes, human hair, eyebrows, eyelashes and, in some cases, beards. The exhibition, which runs through Oct. 31, includes men, women and a child who lived during the region's period of Roman rule.

"The face is the most important feature for recognizing a person," Emese Gábor , a forensic facial reconstruction specialist who sculpted the silicone faces, told Live Science in an email. Although a skull cannot reveal every detail of a person's appearance, reconstruction lets museum visitors encounter the faces as those of "a real human being rather than as skeletal remains," she said.

The entrance to the "Once We Were Like You" exhibit at the Aquincum Museum in Budapest. (Image credit: Gábor Lakos Aquincum Museum Budapest) Rebuilding a Roman face

Aquincum stood on the Danube frontier of the Roman Empire in what is now Budapest. The city was home to a diverse population in the first through fourth centuries, and genetic and archaeological analyses of the individuals in the exhibition point to connections with regions including present-day Italy, Scotland and Syria, as well as Sarmatian groups from the Eurasian steppe and Celtic communities that lived in the region before Roman rule.

The remains of those who lived here have also been unearthed, and continue to be discovered today during the excavation of cemeteries," according to a statement from the museum.

Creating a reconstructed face begins with a high-resolution 3D CT scan of the original skull. Specialists then produce an exact 3D-printed replica, allowing experts like Gábor to work without repeatedly handling or disturbing the ancient remains.

"The latest scientific advances — including 3D scanning, CT imaging, archaeogenetic (ancient DNA) analysis and facial approximation research — are incorporated whenever possible," she said.

"If a hyper-realistic reconstruction is required, I create a mould and cast the face in coloured silicone, finishing it with real human hair, eyebrows, eyelashes and, where appropriate, a beard," she said.

ARC-heo art-REKO Studio ARC-heo art-REKO Studio ARC-heo art-REKO Studio ARC-heo art-REKO Studio ARC-heo art-REKO Studio Ancient DNA can sometimes provide additional clues about pigmentation, including probable eye, hair and skin color. But the results are still approximations, not portraits. For instance, hairstyle, expression and many details of the person’s appearance are usually more speculative.

The woman with the laurel wreath

Of all the people she reconstructed, Gábor said she found it especially difficult to forget the woman known as the Jablonka Road mummy .

The woman's skeleton was relatively well preserved, but the soft tissue on her face had decayed, leaving only the skull. A laurel wreath still rested on her head, and, according to Gábor, her burial contained fine clothing , a spindle for weaving, bird-shaped cork sandals and a painted male portrait that had been placed near her feet. Archaeologists have suggested that the portrait may have represented her husband or father, although his identity is unknown.

The silicon reconstruction of an ancient construction worker. (Image credit: Gábor Lakos Aquincum Museum Budapest) "Based on these details, the archaeological context and the anthropological data, it was the archaeologists who pieced together her story while I reconstructed her face," Gábor said. "That was very moving."

Other individuals selected for the exhibition include those of a young girl who died in childhood and a woman interpreted as a nurse or healer who was buried in a children's cemetery. Some of the other reconstructions include a construction worker, a military officer and a blacksmith.

Two women appear to have met particularly violent or punitive ends. They were buried face down with their legs bound together, Gábor said. The exhibition's interpretation associates one woman with an accusation of witchcraft and the other with poisons, although such details are historical interpretations rather than evidence-based findings from the burials.

Gábor stands in front of a display showing the reconstructed face of a child from Aquincum. (Image credit: Gábor Lakos Aquincum Museum Budapest) "Every reconstruction is a journey," Gábor said. "As I shape each face, I find myself reflecting on that person's life again and again, and by the end, they no longer feel like anonymous remains, but like real people."

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Analyses of the skeletons suggest that many of the individuals endured strenuous physical labor, periods of hunger and chronic inflammation. This evidence led museum curators to conclude that many represented the less wealthy inhabitants of Roman society — people whose names and experiences were unlikely to appear in surviving written histories.

For Gábor, the physical reconstructions offer something that a digital image cannot: Visitors can stand face-to-face with a life-size person, walk around the model and study it from different angles. Her hope is that this encounter encourages visitors to think beyond the scientific data and imagine the full lives that once surrounded the excavated bones.

"When you see a face, you don't just see bones in a display," Gábor said. "You see a person — someone who was born, who grew up, who worked, who loved, who laughed, who struggled, who fought with challenges, who raised children. Some were sick. Not everyone died of illness. Some died in accidents. Some through violence. And eventually, all of them died. That sense of shared humanity helps spark empathy."

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