Knee function through Finite Element Analysis and the role of Miocene hominoids to understand the origin of antipronograde behaviours: the Pierolapithecus catalaunicus’ patella as a test-case study
Although notable attention has been paid to the study of human bipedalism origin and evolution, a full understanding of this question is far to be achieved. In this regard, the role of Miocene hominoids is key to better comprehend the locomotor types observed in living apes and humans. Pierolapithecus catalaunicus is an extinct stem great ape from the middle Miocene (c. 12.0 Ma) of the Vallès-Penedès Basin (NE Iberian Peninsula) and the first undoubted hominoid with an orthograde (erected) body plan. Its locomotor repertoire probably included above-branch quadrupedalism and other antipronograde behaviours. Keep elucidating the adaptive features present in the Pierolapithecus skeleton and its associated biomechanics is still needed to better understand the origin of hominoid orthogrady. This work represents a new biomechanical perspective on the Pierolapithecus locomotion, by studying its patella through Finite Element Analysis (FEA) among a large sample of extant anthropoids. This is the first time that the biomechanical patellar performance is studied by FEA in living non-human anthropoids and a stem hominid. Differences in stress distribution were found depending on body plan and the presence/absence of a distal apex, probably due to dissimilar biomechanical performances. Pierolapithecus’ biomechanical response mainly resembles that of great apes, suggesting a similar knee joint use in mechanical terms. These results underpin previous studies on Pierolapithecus, favouring the idea that a relevant degree of some antipronograde behaviour might take part of its locomotor repertoire. Moreover, our results corroborate the presence of modern great ape-like knee biomechanical performances back in the Miocene.