Fossilized spines recovered from Los Angeles’s La Brea Tar Pits reveal that saber-toothed cats suffered from a high rate of rare spinal tumors and joint disease before going extinct, pointing to severe inbreeding as shrinking Ice Age populations faced their final millennia.
Spinal Tumors and Deformities in La Brea Saber-Toothed Cats
Deep inside the fossil collections of the La Brea Tar Pits, scientists studying the extinct saber-toothed cat Smilodon fatalis have uncovered a stark physical record of a species under extreme biological stress. A comprehensive analysis of thousands of fossilized vertebrae preserved in the asphalt seeps has brought to light an unexpectedly high prevalence of congenital spinal deformities, joint abnormalities, and extremely rare nerve tumors.
Veterinary surgeon Hugo Schmökel of the IVC Evidensia Academy in Stockholm and the Evidensia Academy Sweden and the University of Zürich first noticed signs of disease while visiting the museum collection to examine joint conditions in dire wolves. Driven by professional curiosity, Schmökel returned to examine the cat remains systematically alongside colleagues, inspecting thousands of specimens using physical observation and X-ray scans.
The research team identified 3,722 vertebrae representing at least 849 adult cats, according to Frontiers. Among those bones, investigators cataloged numerous developmental irregularities: 32 vertebrae with incompletely developed arches, 48 fused block vertebrae, and 226 transitional vertebrae where segments formed incorrectly, such as neck bones developing rib-like features.
Most striking were three individual vertebrae recovered from different tar pits featuring hugely inflated, cavernous hollows where nerves and blood vessels pass through the bone. In modern humans and dogs, these widened foramina with smooth, remodeled surfaces are strong indicators of slow-growing spinal nerve tumors that put constant pressure on bone over time.
Joint Disease, Inbreeding, and the Trap of the Tar Pits
The physical toll on these ancient predators extended well beyond the spine. Separate examinations of limb bones from the tar pits revealed that approximately six percent of young adult and juvenile saber-toothed cats, alongside roughly three percent of young adult and juvenile dire wolves, exhibited bone defects consistent with osteochondrosis, a developmental disease affecting joint health in the knee and shoulder.
Paleontologist Mairin Balisi of the Raymond M. Alf Museum of Paleontology in Claremont, California, explained the compounding physical challenges these afflictions created for apex hunters during the waning years of the Pleistocene epoch.
The mechanical demands of hunting made these medical conditions particularly perilous.
With painful spinal tumors and joint degradation compromising their mobility and hunting efficiency, sick or injured predators faced a grim calculus. A wounded predator unable to hunt effectively had to take bigger risks, making them far more likely to approach the crude petroleum seeps and meet the same sticky fate as their prey.
Genetic Bottlenecks and Warnings for Modern Carnivores
Researchers analyzing the spinal pathologies and developmental defects point to a single primary driver behind the surge in rare maladies: population decline and sustained inbreeding. As global climates shifted at the end of the last ice age and giant ice sheets melted, carnivore populations shrank and became increasingly isolated. With fewer potential mates available, harmful recessive genetic variants became concentrated within dwindling gene pools.
Significantly, two of the three Smilodon fossils bearing evidence of spinal nerve tumors date back approximately 12,000 and 13,000 years, placing them right on the doorstep of the species’ total extinction. While scientists have not yet succeeded in extracting usable DNA from La Brea’s saber-toothed cat fossils to definitively prove the inbreeding hypothesis, the pattern of skeletal malformations strongly matches genetic bottlenecks observed in modern inbred canid populations.
The structural insight offers more than just a window into Pleistocene prehistory. According to Frontiers, researchers frame the findings as an ancient warning for today’s embattled big carnivores, demonstrating how habitat loss, poaching, and shrinking wild populations can trigger a destructive genetic squeeze long before the final generation vanishes.
