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Why 'saber-tooth tiger' is the wrong name
Smilodon was never a tiger, and it was not especially close to one. Tigers belong to the genus Panthera, part of the cat subfamily Felinae that also contains lions, jaguars, and every housecat. Smilodon belongs to a separate, extinct subfamily called Machairodontinae, the true saber-toothed cats, whose lineage split from the ancestors of all living cats an estimated 20 million years ago. Homotherium, the other saber-toothed genus that survived into the Pleistocene, is thought to have diverged from Smilodon's own lineage around 18 million years ago, based on ancient mitochondrial DNA sequenced from fossil bone and published in 2017 in Current Biology by Johanna Paijmans and colleagues. By the time modern tigers and lions existed, Smilodon's branch of the cat family tree had already been on its own evolutionary path for longer than most mammal genera survive at all. It is not the only prehistoric animal saddled with a misleading common name; "pterodactyl" has its own, unrelated mismatch between popular usage and what paleontologists actually mean by the term.
Three species are recognized: the small, jaguar-sized Smilodon gracilis (55 to 100 kilograms); the mid-sized Smilodon fatalis (160 to 280 kilograms, about the shoulder height and body length of a modern lion but noticeably more muscular); and the South American giant Smilodon populator, which reached 220 to 470 kilograms and carried the longest saber teeth of any species in the genus, up to 28 centimeters long. Nearly everything popular culture pictures when it hears "saber-tooth tiger" is S. fatalis, largely because hundreds of its skeletons have been pulled out of a single place: the La Brea Tar Pits in Los Angeles, where Ice Age animals became trapped in seeping asphalt and their bones preserved for tens of thousands of years. La Brea holds the largest collection of Smilodon fossils anywhere in the world, which is also why nearly all of the specific research described below comes from that one site.
The bite was weaker than a lion's, and the teeth needed protecting
The two upper canines that give Smilodon its name were slender, blade-like, and finely serrated on both edges, built for a narrow kind of work: a precise, controlled bite rather than a bone-crushing clamp. That specialization came at a cost. Researchers estimate Smilodon fatalis's bite force at only about a third of a modern lion's, and nowhere close to the roughly 8,000-pound bite of Tyrannosaurus rex, since its comparatively small zygomatic arches limited the size of its jaw muscles. To compensate, Smilodon relied on its unusually well-developed, muscular forelimbs to physically wrestle prey to the ground and hold it still, something its skeleton was built for even though its jaw was not, before delivering a bite to a vital area. Its jaw could also open past 110 degrees, versus roughly 65 degrees for a modern lion, wide enough to clear the long canines around a prey animal's throat or flank.
That does not mean the canines themselves were unusually weak. A 2007 study estimated the sideways bending force needed to snap a Smilodon fatalis canine at about 7,000 newtons, close to the roughly 7,440 to 8,243 newtons measured for tiger and lion canines of similar size. The real vulnerability was the risk calculus around using them at all: a lion or tiger can afford to lose or chip a canine and still hunt effectively with a strong bite and sharp claws, but a Smilodon with a broken saber lost its primary killing tool outright. Fossil evidence backs up how much this mattered. Bony growths where the deltoid muscle attaches to the humerus, likely from repeated strain hauling down prey, are common in La Brea specimens, and a study of 1,000 Smilodon skulls found that 36 percent showed eroded parietal bone, the attachment point for the jaw's major muscles, consistent with chronic mechanical stress from repeated stabbing bites.
It carried two sets of fangs for up to two and a half years
That same risk of breakage shaped how Smilodon grew up, and a 2024 study gave the clearest mechanical explanation yet for one of its stranger features. It used the same kind of engineering-modeling approach that a 2023 finite-element study applied to Therizinosaurus's claws, treating a fossil weapon as a physical structure that can be stress-tested rather than just described. Complete skulls from La Brea sometimes show a tooth socket occupied by two teeth at once: a permanent saber tooth growing in alongside the baby, or milk, canine it was replacing. Earlier growth-rate data had already suggested the two teeth could sit together for as long as 30 months of a young Smilodon's adolescence, effectively making it "double-fanged" for two and a half years. What that data could not explain was why evolution would tolerate such an unusual, prolonged overlap instead of shedding the baby tooth quickly the way most mammals do.
UC Berkeley paleontologist Jack Tseng answered that question in a study published 8 April 2024 in The Anatomical Record. Using beam-theory engineering analysis, computer models simulating the sideways bending stress on a growing saber tooth, and physical tests bending plastic tooth replicas, Tseng found that an emerging adult canine is at its most vulnerable to snapping precisely while it is still erupting, before it reaches full length and stiffness. Adding a supportive baby tooth behind it into the model changed the outcome substantially: the milk canine acted like a structural buttress, keeping the growing saber's stiffness in step with the bending forces acting on it and measurably cutting its risk of breaking. "The double-fang stage is probably worth a rethinking now that I've shown there's this potential insurance policy, this larger range of protection," Tseng said in a statement reported by Popular Science. "It allows the equivalent of our teenagers to experiment, to take risks, essentially to learn how to be a full-grown, fully fledged predator."
One La Brea specimen studied for the paper, a partial upper jaw showing a fully erupted baby saber next to an adult tooth just breaking through the gum, let Tseng estimate the animal's age at death at 12 to 19 months, right in the middle of this double-fanged window. Juvenile and adolescent Smilodon fossils are rare at La Brea overall, which researchers take as a sign that young cats stayed hidden at denning sites during hunts, dependent on parental care and protected teeth while they were still too dangerous to themselves to risk using a half-grown weapon in earnest.
A newly published clue to how it went extinct
Smilodon fatalis went extinct roughly 10,000 years ago, part of the broader end-Pleistocene extinction that wiped out most of North America's large mammals, mammoths and giant ground sloths included, between about 13,000 and 9,000 years ago. A study published 27 July 2026 in Frontiers in Veterinary Science, only weeks before this article, adds a specific and previously undocumented clue about the animal's final years. Hugo Schmökel, a veterinary spine surgeon at IVC Evidensia Academy in Stockholm, had been visiting the La Brea collection to study joint disease in dire wolves when he noticed something in the Smilodon vertebrae nearby. "As a spine surgeon for dogs and cats, I was immediately interested and went back twice to La Brea," Schmökel told Science News.
Schmökel and his colleagues systematically examined more than 3,000 Smilodon vertebrae from the La Brea collection, mostly lumbar bones from the lower back, using visual inspection and X-ray scans. They documented hundreds of spinal deformities, including fused vertebrae and abnormally split bone. Three individual cats stood out with a specific, normally rare condition: the small openings in vertebrae that let nerves and blood vessels pass through were hugely enlarged into cavernous hollows, a pattern that in modern humans and dogs is caused by slow-growing tumors on the spinal nerve. Those tumors affect no more than about 0.38 people per 100,000 today; the researchers calculated the rate in the La Brea Smilodon sample at roughly 1,000 times higher. Two of the three affected fossils dated to 12,000 and 13,000 years ago, shortly before the species disappeared entirely.
Schmökel's team connects the pattern to inbreeding: similar spinal deformities show up in inbred modern gray wolf populations, and DNA and skeletal evidence from other Ice Age megafauna that went extinct around the same time, including mammoths, woolly rhinos, and giant deer, shows comparable signs of a shrinking, increasingly inbred gene pool in their final years. Paleontologist Mairin Balisi of the Raymond M. Alf Museum of Paleontology, who was not involved in the study, told Science News the tumors would likely have compounded the problem, since Smilodon's hunting style "would have required bracing on their hind legs, pulling back and then launching themselves at their prey" against animals that "would not go down peacefully." A cat in chronic spinal pain may have been more likely to target easy, trapped prey in the tar itself. "This might be how extinction happens," Balisi said. "You start getting smaller population sizes and more isolated populations, resulting in less genetic diversity and more inbreeding." No usable DNA has yet been recovered from La Brea's Smilodon fossils, so Balisi cautioned that the inbreeding case remains circumstantial: "the real smoking gun would be genetic evidence."