Strange beast or strange poison: What is hidden in the frozen soil of the "Earth's Refrigerator"?

As climate change intensifies, parts of the polar permafrost are beginning to melt, revealing secrets that have been frozen for millions of years - in addition to lifelike ancient animals, some ancient "threats" are also buried in the permafrost.

Interview experts

Li Qihan (Researcher, Institute of Medical Biology, Chinese Academy of Medical Sciences)

The howling snowstorm finally stopped after days of howling, and the white glacial world began to wake up. In a cave buried under the thick snow, a female cave lion was trying to resist its biggest enemy - hunger.

The lioness gently licked the sleeping cub awake. The cub in her arms was only one or two months old and covered with golden fur. As the cub grew rapidly, its curiosity about the outside world became stronger and stronger. It would soon be able to eat meat. The wildness of nature called it to enter the world covered with ice and snow.

So, the hungry lioness took her cubs and went outdoors on a sunny winter day to look for food.

▲The painter imagined a cave lion hunting scene, created in 1920 (Source: Wikipedia)

Suddenly, a part of the ground buried by the snow caved in - it turned out that a huge, bottomless crack was hidden under the snow! However, it was too late. The lion cub rolled over and fell without any time to react. Its young body was instantly crushed under the scattered ice, snow and gravel...

We can only imagine what happened to this ancient lion cub, but what is certain is that its life was abruptly frozen in the Ice Age.

In the endless darkness and freezing cold, 28,000 years passed in the blink of an eye. The arrival of a mammoth ivory collector named Boris Berezhnev allowed the cave lion cub, which was frozen in the permafrost, to "see the light of day again."

Frozen "Ancient Animal Cemetery"

500,000 years ago, there were a large number of primitive lions living on the African continent. As time went on, some lions "left Africa" ​​and migrated to Europe. Their descendants gradually adapted to the rugged mountains and cold climate there, and eventually evolved into cave lions. These now extinct cats were much larger than modern lions. Between 300,000 and 100,000 years ago, they roamed the vast land of the Russian Far East, feeding on mammoth cubs, camels and bison, and finally disappeared 10,000 years ago.

In 2017, Boris found a male cave lion cub near a river in the Yakutia region of East Siberia and named it "Boris". A year later, less than 15 meters away from where "Boris" was found, he found another female cave lion cub "Sparta".

▲A close-up photo of the female cave lion cub "Sparta", whose whiskers are still clearly visible (Source: Stockholm University)

Compared to Boris, whose remains are partially damaged, Sparta may be "the best-preserved Ice Age animal ever found," said Raúl Dahlen, a researcher at the Stockholm Center for Paleogenetics in Sweden.

Sparta is covered with golden fur and does not appear to have any wounds or injuries. It has its eyes closed and its mouth slightly open, as if it is sleeping quietly. From the distinct whiskers around its mouth to its sharp claws, Sparta, who has become a mummified animal under natural conditions, is almost exactly the same as it was 28,000 years ago, except that it has become shriveled.

▲Pictures a, c, e, and f are "Sparta", and pictures b and d are "Boris" (Source: Academic journal "Quaternary")

"We used a CT scan and found damage to its skull and dislocated ribs. Given its state of preservation, we think it must have been buried soon after death, perhaps in a mudslide or a crack in the permafrost," said Darren.

According to the research, in addition to a slight deformation of the skull, Sparta's hind limbs and tail were also very flattened, as if it had been under great pressure. When Boris was excavated, his hind limbs were stretched out and his claws were slightly flattened dorsally and ventrally, which may be because he struggled or paddled for water before death.

▲The skeleton outline of "Boris" under CT scan (Source: Academic Journal "Quaternary")

At first, the researchers thought that the two lion cubs that were not far from each other might be a "family". However, after some testing, people were surprised to find that the two "mummies" were not only not siblings, but their death times were 15,000 years apart - "Boris" was 43,000 years old!

Both cave lion cubs died here. Was this a dangerous place during the Ice Age tens of thousands of years ago? On the contrary, this may have been a habitat favored by ancient creatures.

It is reported that in the same excavation area as the two lion cubs, researchers also found even older animal mummies: a 46,000-year-old horned lark and an 18,000-year-old "puppy" that resembled a dog and a wolf. If there is anything in common between these animals, it is that they all look "like they had just died a few days ago."

Various ancient creatures under the frozen soil

In fact, the discovery of frozen soil life is not uncommon. The extreme cold in the polar regions can not only stop the heart of ancient creatures that encounter unexpected events, but also pause the clock of decay and deterioration.

In 2018, also in the Yakutia region of eastern Siberia, scientists discovered a young horse mummy dating back 40,000 to 30,000 years. The foal's hooves, tail and even the area around its nostrils were still "hairy" and were still clearly visible when it was excavated.

▲The young horse mummy found in the frozen soil still has vivid hair details (Source: Northeastern Federal University, Russia)

In 2020, scientists discovered another woolly rhino mummy in the permafrost of the area. When this woolly rhino, which is 50,000 to 20,000 years old, was discovered, 80% of its brown hair was very well preserved. In addition to its teeth and bones, even its last meal before it fell into the water and died was well preserved in its intestines. Because of this, it is also regarded as the best preserved woolly rhino specimen to date.

In 1993, Russian scientists discovered a female human mummy who had died at least 2,500 years ago in the permafrost of the Ukak Plateau in the Altai Mountains. When unearthed, the female corpse was in very good condition. Whether it was her elastic skin or the exquisite deer head tattoo on her arm, it shocked the world. People called her "Princess Ukak", and some even believed that this was "one of the most important archaeological discoveries of the 20th century."

▲The tattoo on the shoulder of "Princess Ukak" (Source: Siberian Times)

With the increase of human activities in permafrost areas in recent years, more and more lives that "died in an untimely way" in ancient times have appeared before the world. Among them are not only extinct rare birds and animals, but also microorganisms that are invisible to the naked eye. After millions of years in the permafrost, they have not only seen the light of day again, but some have even been "resurrected"...

In June this year, Russian scientists published a research paper in Contemporary Biology, saying that they found bdelloid rotifers that had been "sleeping" for at least 24,000 years 3.5 meters below the permafrost in Siberia. Later, in the laboratory, scientists successfully "resurrected" some of them!

It is understood that bdelloid rotifers are a kind of freshwater invertebrate organisms, which are very small and can only be seen under a microscope. In the nearly 40 million years of evolution, bdelloid rotifers have evolved a very tenacious vitality - in harsh environments such as anhydrous, freezing, low temperature, and low oxygen, they can still survive in a "super long standby" state without being completely dehydrated.

Scientists have previously conducted experiments in which they froze modern bdelloid rotifers in a low-temperature freezing environment of -20°C, and these microorganisms could still be "awakened" 10 years later.

▲Under the microscope, at least 24,000 bdelloid rotifers are sleeping (Source: AFP)

It is reported that after scientists repeatedly froze and thawed these ancient "little zombies" found in the frozen soil, they found that these microorganisms would automatically turn on the "protection mode" in extreme environments to prevent the cells from freezing. The thawed "resurrected" bdelloid rotifers can also reproduce parthenogenetically to produce clones with exactly the same genes as the original body.

The melting “refrigerator” and hidden worries

Ancient creatures are "traveling through" to the modern era more and more frequently. Is this a blessing or a curse for humans?

For the Earth, the permafrost is like a huge natural refrigerator. In addition to various large organisms, there are also many more bacteria and viruses that modern humans have never encountered.

In 2014, a joint laboratory of the French National Center for Scientific Research and the University of Marseille announced that researchers had discovered the "Siberian Broad-mouthed Pot Virus" in permafrost samples collected in Russia's Far East four years ago.

The Pithovirus is a super-large virus with a genome larger than most known viruses. Its diameter can exceed 0.5 micrometers and can even be seen clearly under an optical microscope. The virus discovered by French researchers was buried 30 meters underground in a sediment layer. They found in their experiments that although the virus had been frozen in the permafrost for at least 30,000 years, it was still contagious after "resurrection" and successfully infected amoeba.

▲Siberian broad-mouthed jar virus under a microscope (Source: AFP)

It is not known what threat Siberian Pithovirus would have posed to prehistoric species, but at least for modern humans, it is safe. Like many giant viruses, Pithovirus can infect amoebas but not humans.

"We can't say it's 100% impossible, but the chance is very small." Li Qihan, a researcher at the Institute of Medical Biology, Chinese Academy of Medical Sciences, told reporters that amoeba is very different from vertebrates in physiology, "and they are too far apart in kinship, so the possibility of cross-border transmission to humans is very small."

The premise for a virus to infect the human body is that it can bind to human cells. This process relies on the binding of proteins on the surface of the virus to certain protein receptors on the surface of human cell membranes. However, the Siberian Pittospor virus has been frozen in the permafrost for more than 10,000 years, resulting in its long-term "absence" from biological evolution, which greatly reduces the probability of it matching the cell receptors of higher organisms 10,000 years later.

"Only by 'scrambling' with humans for a long time can they have the opportunity to 'find out the way' and mutate into a pattern that can deceive the human immune system," Li Qihan explained. However, scientists will still be very cautious. "Generally speaking, when scientists conduct research on prehistoric biological samples, they will take adequate protective measures and disease screening, and conduct experiments in an environment that ensures biosafety," he said.

Compared with prehistoric microorganisms that have been sealed for a long time, pathogens that have been buried for a short time are more dangerous: in 2016, a mysterious anthrax outbreak occurred in Russia's northern Siberia, killing a 12-year-old boy, infecting dozens of people, and killing more than 2,300 reindeer. The culprit of this epidemic was none other than the anthrax bacteria that had been sealed in the permafrost for more than 75 years.

According to a Russian government spokesman, the last anthrax outbreak in the area was in 1941. In order to save wood, people chose to bury the carcasses of reindeer infected with anthrax instead of burning them. Invisible "time bombs" were buried under the frozen soil. Decades later, the local weather became extremely hot, and the heat wave caused part of the permafrost to melt. The carcasses of the sick reindeer were exposed again, and the boy who accidentally ate the frozen meat of the sick reindeer was subsequently infected with anthrax.

As the greenhouse effect worsens, the polar permafrost, the "fridge of the earth," is also thawing and even melting at an accelerated rate. What will be waiting for humans under the cold ice?

Written by reporter Wang Xueying Edited by Ding Lin

New Media Editor/Lv Bingxin

Produced by: Science Central Kitchen

Produced by: Beijing Science and Technology News | Science Plus Client

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