Sabertooth cats and their relevance for early hominid diet and evolution

Abstract

Large carnivores structure the character of scavenging opportunities in any environment. In Pliocene and early Pleistocene Africa there were three large sabertooth cats sympatric with the ancestors of the modern felid community, and scavenging opportunities were presumably different from those in modern Africa. An understanding of a possible scavenging niche for early hominids must articulate knowledge gained from actualistic research with detailed reconstructions of extinct carnivore paleoecology. Contrasting skeletal and dental anatomy suggest that sabertooths and modern felids were ecologically distinct. Evidence from functional morphology and fossil associations elucidates the distinctions. Sabertooth incisor and carnassial morphology indicates extreme flesh specialisation and lack of bone-crushing ability. Sabertooth cranial morphology and fossil associations suggest a specialisation upon very large prey. The post-cranial morphology of sabertooths indicates a dense woodland and forest habitat preference. This implies that two distinct large carnivore communities existed in the Pliocene and early Pleistocene: a mixed and open habitat community composed of the ancestors of the extant carnivore community plus Chasmaporthetes, and a closed habitat community dominated by the sabertooths. Scavenging opportunities in the closed habitat community would have been much better than in more open habitats. Homo habilis with its inferred arboreal abilities could have passively scavenged very effectively in dense woodlands and forests. Paleoenvironmental and paleontological data indicate that these closed habitats shrunk after 1·7 million years ago and the sabertooths probably went extinct in sub-Saharan Africa. Homo habilis perhaps increasingly utilised more open habitats and would have been forced to confront large predators to gain adequate scavenging returns. Archaeological data of stone tool raw materials and site placement suggests that early hominids switched from an emphasis on dense woodland habitats to increased usage of more open habitats after 1·6 million years ago. Confrontational scavenging along with increased predation pressure may have contributed to the morphological changes associated with the shift to Homo erectus.