Sabre-Toothed Cats Were A Diseased, Inbred Mess Before They Went Extinct, New Research Suggests

If you have ever woken to find a saliva-soaked ribbon across your face, or discovered an unfortunately slaughtered mouse ‘present’ inside your slippers, you will know that even the smallest pet cat is evolutionarily equipped for hunting.

The domestic cat’s distant relative, however, was a far more formidable feline. Smilodon fatalis branched away from the ancestors of modern cats and tigers 20 million years ago.

Weighing as much as 600 pounds (270 kilograms), Smilodon fatalis was part ‘cat’ and part cruise missile: an ambush predator armed with scimitar-like teeth.

Its Greek-Latin name, in fact, roughly translates as “deadly knife-tooth”, a reference to the terrifying killing fangs set in its jaws.

A representation of S. fatalis at the Royal Tyrrell Museum, Drumheller, Alberta. (Chris Woodrich/Wikimedia Commons/CC BY-SA 4.0)

Smilodon fatalis may have been inbred before extinction

A recent study in Frontiers in Veterinary Science has found indications that this powerful predator became inbred and developed spinal abnormalities before leaving the evolutionary stage around 12,000 years ago, at the close of the last Ice Age.

Using optical techniques and computed tomography (CT) scans, the team assessed more than 3,700 vertebrae from at least 849 individual S. fatalis. They were searching for evidence of injuries, disease and genetic defects.

The animals died in, and their skeletal remains were preserved by, the La Brea Tar Pits in Los Angeles – possibly the “world’s richest ice age fossil site”.

Tar pits have become popular fixtures in mass media, appearing in famous programmes including The Flintstones and The Simpsons, as well as a perhaps less iconic 20th-century slapstick comedy featuring former Beatles drummer Ringo Starr as a ‘caveman’.

They were deadly places, too.

“The tar seeps were a carnivore trap,” the researchers explain. “A large herbivore that became mired in the asphalt inadvertently would attract large carnivores and scavengers, which would themselves become entrapped in great numbers.”

Spinal disease in the La Brea Tar Pits specimens

The S. fatalis vertebrae showed a broad range of pathologies, some severe, with numerous signs pointing to chronic inflammatory disease. Researchers also found more than 200 congenital spinal malformations and almost 50 fused vertebrae, alongside evidence of abnormal bone growth and skeletal deterioration.

They further identified lower-back, or lumbar, vertebrae from three separate animals that showed signs of spinal nerve tumours (SNTs), which can arise from genetic mutations.

Three cases may not seem substantial.

Yet, in relation to the specimens included in the study, the researchers calculate an SNT prevalence of 353 per 100,000 individuals. They note that this greatly exceeds even the highest estimated incidence in humans, at just 0.38 per 100,000 people.

A Smilodon fatalis vertebra, showing signs of an enlarged cavity where a spinal nerve tumour may have grown (green arrow), as well as an illustration of its potential size. (Schmökel et al.,* Front. Vet. Sci.*, 2026)

For a population already in decline, the effects of these congenital malformations may have been devastating.

Most people with SNTs, for instance, experience pain. In dogs, these tumours commonly produce pain as well as muscle wastage and lameness – problems that would have severely impaired an ancient predator’s ability to hunt.

This could perhaps explain why the tar pits contain so many hundreds of Smilodon specimens.

An animal coping with diminished function and disability may have salivated – and become less cautious – when it saw a large, succulent herbivore struggling to escape a black, bubbling pool of tar.

What inbreeding in Smilodon fatalis could mean today

Although the physical evidence lends considerable support to inbreeding, proving the scenario may be impossible without DNA analysis. Unfortunately, the researchers note that “as is the case with all fossils from the LBTPM, no soft tissues are preserved”.

Nevertheless, the findings carry troubling implications today, as animal populations face the combined pressures of climate change, environmental encroachment and habitat loss.

Related: There’s One Predator That Terrifies Bears And Mountain Lions Alike

“There is evidence that due to dramatically declining population numbers, there was an increasing occurrence of inbreeding in mammals at the end of the Pleistocene, with different health consequences,” the researchers conclude, adding that S. fatalis was not alone:

“DNA analysis of mammoths found in the permafrost revealed a high degree of inbreeding before they became extinct, potentially causing serious diseases such as diabetes mellitus and sensory deficits.”

This research appeared in Frontiers in Veterinary Science.

This article was fact-checked by Rachel Garner and edited by Rebecca Dyer. Although we take pride in our process, we are only human. If you find an error, please let us know.