11/27/2022 0 Comments Chimpanzee hand configurationvertical climbing and quadrumanous scrambling), as their thumb is relatively short compared with the other fingers so that it is not involved during knuckle-walking. Both bonobos and chimpanzees possess a very diverse locomotor repertoire, but the thumb is predominantly used during arboreal locomotion (e.g. 2015), while the split in the genus Pan appears to have happened between 2 and 1 million years ago (Prado-Martinez, 2013 Kuhlwilm et al. The common Homo- Pan ancestor lived 7–13 million years ago (Young et al. Within the extant primates, the bonobo ( Pan paniscus) is one of the modern human's closest relatives, sharing approximately 98.7% of their genetic blueprint with modern humans (Prüfer et al. Despite the great importance of the thumb in human evolution, key to the unique human dexterity, a complete understanding of the adaptive signals and form–function relationship in the primate thumb is lacking. As the primate hand displays many varieties of phenotypes where form and function of the thumb are closely correlated, understanding these phenotypes in closely related primate species may facilitate the interpretation of function in an evolutionary context. Despite the fact that non-human primates use their hands in locomotion and manipulation, many also show advanced manipulative abilities, used in grooming and for processing food or for making and using tools. The modern human ( Homo sapiens) hand is a prime example of such dexterity, with a thumb fully devoted to manipulation. The thumb plays a key role in the functioning of the primate hand, known for its unprecedented dexterity. It is conceivable that differentiation and individualization of the hand muscles rather than relative muscle development explain the higher level of dexterity of humans compared with that of bonobos. Most importantly, bonobos show a higher degree of functional coupling between the muscles of the thumb, index and lateral fingers than observed in humans. The bonobo thumb musculature has a lower force-generating capacity than observed in the human specimen, but the estimated maximal intra-articular pressure is higher in bonobos. Our results show that the force-generating capacity for most functional groups of the extrinsic and intrinsic hand muscles in bonobos is largely similar to that of humans, with differences in relative importance of the extensors and rotators. Furthermore, we used medical imaging to quantify the articular surface of the trapeziometacarpal joint to estimate the intra-articular pressure. We performed detailed dissections of unembalmed specimens to collect quantitative datasets of the extrinsic and intrinsic hand musculature, in addition to qualitative descriptions of the forelimb muscle configurations, allowing estimation of force-generating capacities for each functional group. To understand how morphology may influence dexterity, we investigated the functional anatomy of the bonobo hand using a unique sample of eight bonobo cadavers, along with one chimpanzee and one human ( Homo sapiens) cadaver. Despite the close phylogenetic relationship between bonobos and humans, detailed quantitative data of the bonobo forelimb musculature remains largely lacking. The bonobo ( Pan paniscus), the closest extant relative to modern humans together with the chimpanzee ( Pan troglodytes), also possesses good manipulative capabilities but with a lower level of dexterity compared with modern humans. The human hand is well known for its unique dexterity which is largely facilitated by a highly mobile, long and powerful thumb that enables both tool manufacturing and use, a key component of human evolution.
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