The ice patches surrounding the Indigirka River and its tributaries in northeastern Russia serve as a graveyard for the Ice Age: mammoths, woolly rhinoceros, saiga, and bison that lived and died in the Last Glacial Period. Mammoth tusk collectors trawl the ice for tusks and other bones poking out from the melting permafrost, but occasionally they stumble on bodies that have been frozen for tens of thousands of years. In 2017 and 2018, tusk collectors found two mummified cave lion cubs, a species that has been extinct for thousands of years and likely resembled modern lions. In 2020, a tusk collector unearthed another, even rarer ancient kitten: a frozen saber-toothed cat cub, as Asher Elbein reported in The New York Times.
Despite their presence in our prehistorical imaginings—such as a starring role in the Ice Age franchise—the actual soft-tissue appearance of saber-toothed cats remained a mystery to scientists. So this new cub offers the first-ever glimpse at how the cats appeared in real life, about 35,000 to 37,000 years ago. The term saber-toothed cat refers to a plethora of cat-like species with elongated teeth, and the most famous—and perhaps most extravagantly toothed—belonged to the genus Smilodon. Scientists identified the new cub as Homotherium latidens, a species in another genus that contained the "scimitar-toothed cats," as these cats had curved canines that were smaller than Smilodon's. The researchers' paper describing the new kitten was recently published in Scientific Reports.
Unlike the frozen lion cubs, the saber-toothed cub belongs to a family of animals only distantly related to modern felines, a family with no surviving species. This renders the frozen cub enormously significant. As Riley Black writes in National Geographic, the chances of discovering a saber-toothed cat in a chunk of ice were slim when compared to an animal like a mammoth, as prey far outnumber apex predators. "For the first time in the history of paleontology, the appearance of an extinct mammal that has no analogues in the modern fauna has been studied," the authors wrote in the paper.
Even at its young age, the cub already diverged physically from modern lions. Its neck was powerfully muscled, more than twice as thick as that of a lion cub. It had wider, rounder paws than a lion's, but its paw pads were square, unlike the oval ones of modern cats ("beans," in the scientific parlance). The saber-toothed kitten also lacked a carpal pad—the extra pad of skin that can be found further up a cat's leg. Carpal pads help cushion cat's falls and provide traction as they run. But this lack of carpal pads was likely an adaptation to walking in snow and low temperatures, the authors explain.
But this is the marvel of permafrost: how it can preserve the soft trappings of an animal—its fur, its whiskers, and the skin of its paw pads—as if tens of thousands of years did not actually come to pass. Some of the cat's more diaphanous features have vanished, such as its eyelashes. But otherwise the saber-toothed cub looks like it died yesterday. Its claws are still sharp. Its broken whiskers still jut out of its upper lip. Based on the eruption of the cub's baby teeth, the researchers estimate it was three weeks old when it died.
Perhaps the cub's age contributes to its surreal appearance—being both 37,000 years old and also a baby. Its soft, thick coat was a dark toffee brown, a color that could have changed as the cub grew up (and also may have been affected by the freezing process). Its fur was short, rarely longer than an inch, longest on the cat's back and neck. The corners of its mouth were fringed with longer tufts of pale fur, perhaps hinting at a future mane. It's not clear how this cub died. But if the cub had grown up, perhaps it wouldn't have mummified, dying somewhere less serendipitous to preservation.
Fossils rarely make me emotional. The extremely slim chance that an individual animal's presence would be preserved across thousands or even millions of years makes their death seem more like a wonder than a tragedy. And when animals are reduced to fossilized bones, as they often are, their life is harder to imagine than their death. This remove makes the distance between my life and theirs seem even greater. But that is the miracle of frozen mummies, how their lifelike appearance seems to collapse time, reminding us that the worlds we were born into were not so different, after all.
I often feel a twinge of grief upon the discovery of a mummified baby of any species—a creature that, for whatever reason, died before it could come into its own particular body, perfectly adapted to a lost world. This twinge has never been greater, perhaps because this saber-toothed cub is so stinking cute. Unsurprisingly, the paleoart community has already leapt to memorialize the little Homotherium, even imagining its final days with its mother. But then I remember how this newly discovered cub will give us insight into the many cubs that did survive, grow up, and prowl the tundra of our frozen Earth.
