Saber fanged cats ruled the Pleistocene and survived the last Ice Age, but went extinct at roughly the same time that humans were discovering agriculture. This is the first time in millions of years that sabercats haven't roamed the planet. But we might just survive long enough to see them return.
Evolution does not precisely repeat itself. Species are unique entities, modified from their long line of ancestors, that exist for only a limited time before they expire. Some species will leave altered descendants, while others will be the last of their kind. Still, in a general, anatomical sense, what was old can become new again through an evolutionary phenomenon known as convergence. Traits of distantly-related animals can evolve into similar forms through adaptation, and we know this happened several times with cat-like, saber-fanged predators. It could very well happen again.
Exactly when the last sabercat perished was never recorded for history. The prehistoric record of bones and teeth suggest that these felids' last gasp came around 10,000 years ago – only yesterday from the perspective of Deep Time.
Image by Dallas Krentzel
This recent extinction isn’t just a disappointment to fans of gorgeous, big cats with giant teeth. It's also frustrating for paleontologists who know that prehistoric people in the Americas must have witnessed sabercats, yet somehow neglected to leave behind art of what these cats looked like and how they behaved. A carved figurine was thought to represent the wide-ranging scimitar-toothed cat Homotherium, but was later found to be a representation of a juvenile lion. Damn.
The Evolution of Long-Fanged Predators
There isn’t a standard definition of what makes a sabertooth a sabertooth. Flattened, elongated canines are essential of course, but animals such as lemurs, monkeys, and musk deer have such teeth today and we don’t call them saberprimates or saberdeer. (My apologizes if that comment just inspired the next SyFy original movie.) And even among feliform predators, there was a spate of long-fanged predators of one stripe or another.
Evolving before true sabercats, and coexisting with them for millions of years, were the nimravids. These predators – such as museum exhibit favorite Hoplophoneus – were cousins of cats that lived between 40 and 7 million years ago, but were not actually close relatives of sabercats themselves. You need to be a hardcore paleontologist to tell them apart.
Nimravids were so cat-like that their distinguishing features are all subtle anatomical traits. And even among true felids, there were sabercat imitators. Dinofelis, often called a “false sabertooth”, was a wide-ranging cat that also convergently developed very long fangs during its span of 5 to 1.2 million years ago. And there was even a distantly-related marsupial predator that sported impressive saber fangs – Thylacosmilus, the “pouch knife.” Saber fangs were in fashion for a very long time.
But the true, formidable sabercats belonged to a specific group called the machairodonts. This is the family of Smilodon and Homotherium – a carnivorous reign that started about 23 million years ago only to be snuffed out at the end of the last Ice Age, roughly 10,000 years ago. No one knows why. Supposedly the cats disappeared because their favored prey – such as prehistoric species of camel and bison – went extinct, but this only moves the problem one step further back to the much-contested trigger of the Pleistocene extinction.
Saber-Animals Are Everywhere
All the same, the repeated evolution of saber-fanged cats, or cat-like creatures, over the past 40 million years suggests a common evolutionary thread that may repeat itself. There may even be a good candidate for an ancestor of future sabercats living today.
With their mouths closed, clouded leopards don’t look like possible progenitors of sabercats. Their canine teeth don’t distinctively jut out from their lips like those of a Smilodon. But in a 2006, anatomist Per Christiansen outlined how clouded leopards have some traits and abilities that are startlingly similar to the totally extinct true sabercats.
For one thing, Christiansen found that clouded leopards have longer canines relative to their skull length than any other living cat. Their canines might not stick out below their lower jaws, but their dental cutlery is still quite impressive and of the same general proportion as sabertooth cats such as Homotherium. Aspects of the cat’s jaw joint and facial part of the skull also more closely resemble archaic sabertooths rather than modern big cats, and, perhaps most impressive of all, clouded leopards are able to drop their lower jaws to a gape of about 90 degrees. This extreme yawn was thought to be only possible for sabercats, but the clouded leopard has challenged that notion.
Image via Paul Copsey
Christiansen cautioned about counting clouded leopards as modern sabertooths, especially since the cats most closely resemble sabercats that had relatively short canines compared to the more famous forms, yet both the modern cat and the extinct carnivores shared a variety of features required for a large gape. The cat convergently evolved “sabertooth characters” and could act as a proxy for how early sabercats bit and killed their victims. In fact, clouded leopards might embody another way to be a sabertoothed predator.
After decades of debate that variously saw sabercats as stabbers, slicers, climbers, and even vampires, paleontologists have come to a consensus view that Smilodon and kin employed their fangs in a shear bite to the soft throats or bellies of their victims. If their bite didn’t immediately kill, the trauma and blood loss would have quickly accomplished their carnivorous goal.
But clouded leopards don’t bite this way, nor do they use the same techniques as living big cats. Instead, as Christiansen pointed out, they often kill prey – and each other – by a strong bite through the nape of the neck. Perhaps early sabertooths did the same. Even if not, the behavior of clouded leopards shows another route by which traditional “sabertooth” characteristics can evolve.
Sabercats of the Future
While clouded leopards may not yet be counted as fullblown sabertooths, I have to wonder if a few more million years might allow their descendants, in the right circumstances, to reprise the role of the lost Smilodon. Given how many times saber fangs evolved in different predatory lineages over the past forty million years, future sabercats are a distinct possibility.
We’re in a megafaunal lull. The absence of the Ice Age mammoths, sloths, and other creatures is still apparent. A scant few thousand years isn’t long enough for a resurgence in megafauna, much less in a time when our species is so concerted on cutting them back. But if saber fangs are specializations for deadly nape bites or cutting large chunks of flesh from large prey, then there’s a chance sabercats could return. Especially if we doom ourselves to extinction – which I hope is not going to be the case – life will continue to adapt and evolve from the survivors. Cats will almost certainly be among them.
Even if we lose charismatic cats such as the clouded leopard, I have a feeling that domestic cats – spread all over the world almost everywhere that our species lives – could be the rootstock for future sabercats that stalk the huge descendants of rats and rabbits in a future inhabited by Dougal Dixon-ish creatures. The next time your housecat yawns, or you lift their lips to see those sharp teeth they often use to bite the hand that feeds, you might be seeing the prototypes for future saber fangs.
Brian Switek is the author of My Beloved Brontosaurus, and creator of the paleontology blog Laelaps.