Smilodon
Extinction

Along with most of the New World Pleistocene megafauna, Smilodon became extinct by 10,000 years ago in the late Pleistocene extinction phases of North and South America. Its extinction has been linked to the decline and extinction of large herbivores. Hence, Smilodon could have been too specialized at hunting large prey and may have been unable to adapt. Indeed, by the Bølling–Allerød warming event and before the Younger Dryas cooling event, S. fatalis showed changes in cranial morphology that hint towards increased specialization in larger prey and/or evolution in response to competition with other carnivores. However, a 2012 study of Smilodon tooth wear found no evidence that they were limited by food resources. Other explanations include climate change and competition with Homo sapiens (who entered the Americas around the time Smilodon disappeared), or a combination of several factors, all of which apply to the general Late Pleistocene extinction event, rather than specifically to the extinction of the saber-toothed cats. One factor often cited here is the cooling in the Younger Dryas, which may have drastically reduced the habitable space for many species. In terms of human influence, there is evidence of a fire-induced regime change in Rancho la Brea that preceded the extirpation of megafauna in the area, with humans most likely responsible for the increase in fire intensity.

Writers of the first half of the twentieth century theorized that the last saber-toothed cats, Smilodon and Homotherium, became extinct through competition with the faster and more generalized felids that replaced them. It was even proposed that the saber-toothed predators were inferior to modern cats, as the ever-growing canines were thought to inhibit their owners from feeding properly. Since then, however, it has been shown that the diet of machairodontines such as Smilodon and Homotherium was diverse. They do not seem to have been limited to giant animals as prey, as suggested before, but fed on whatever was available, including bovines, equines and camelids. Additionally, non-machairodontine felids such as the American lion and Miracinonyx also became extinct during the Late Pleistocene, and saber-toothed and conical toothed felids had formerly coexisted for more than a million years. The fact that saber-teeth evolved many times in unrelated lineages also attests to the success of this feature.

The youngest direct radiocarbon date for S. fatalis differs from that of S. populator by thousands of years, the former just before the Younger Dryas cooling event and the latter by the early Holocene. The latest S. fatalis specimen recovered from the Rancho La Brea tar pits has been dated to 13,025 years ago. A specimen of S. fatalis from Iowa dates to 13,605–13,455 years Before Present (BP). The latest Smilodon populator remains found in the cave of Cueva del Medio, near the town of Soria, northeast Última Esperanza Province, Magallanes Region in southernmost Chile have been dated to 10,935–11,209 years ago. The most recent credible carbon-14 date for S. fatalis has been given as 11,130 BP. However, such radiocarbon dates are likely uncalibrated, meaning that they were not adjusted from calendar years to regular years. As a result, the dates appear younger than they actually are. Therefore, the S. fatalis specimen from Rancho La Brea is the youngest-recorded of the species, suggesting extinction before the Younger Dryas based on its last appearance in California as opposed to other regions where megafauna declined by the Younger Dryas.
keywords:letter_frequency