Tens of thousands of years before the last saber-toothed cat disappeared, the species was already being undone from within — its bones quietly recording the cost of isolation and diminishing numbers. A study of fossils preserved in the La Brea Tar Pits reveals that Smilodon fatalis suffered extraordinary rates of spinal deformity and nerve tumors, the biological signature of sustained inbreeding as ice age habitats contracted. What the tar preserved was not merely death, but the long unraveling that preceded it — a warning written in bone that speaks as much to the present as to the prehistori