The human semicircular canals orientation is more similar to the bonobos than to the chimpanzees

• Published in: PloS one Vol. 9; no. 4; p. e93824
• Main Authors: El Khoury, Marwan, Braga, José, Dumoncel, Jean, Nancy, Javotte, Esclassan, Remi, Vaysse, Frederic
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.04.2014; Public Library of Science (PLoS)
• Subjects: Adaptation; Adaptations; Adult; Analysis; Animals; Biology and Life Sciences; Brownian motion; Brownian movements; Canals; Chimpanzees; Collections; Computed tomography; Convergence; Deformation; Deformation mechanisms; Dentistry; Evolution; Female; Fossils; Functional morphology; Genetic aspects; Genetic diversity; Genetic Variation; Genomes; Hominids; Homo sapiens; Human motion; Humans; Infant; Laboratories; Male; Medical imaging; Monkeys & apes; Morphology; Museums; Pan paniscus; Pan troglodytes; Phenotype; Phylogeny; Physiological aspects; Posture; Pygmy chimpanzee; Radiography; Random walk; Semicircular canals; Semicircular Canals - anatomy & histology; Semicircular Canals - diagnostic imaging; Social Sciences; Studies; Taphonomy; Tomography; France
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0093824

For some traits, the human genome is more closely related to either the bonobo or the chimpanzee genome than they are to each other. Therefore, it becomes crucial to understand whether and how morphostructural differences between humans, chimpanzees and bonobos reflect the well known phylogeny. Here we comparatively investigated intra and extra labyrinthine semicircular canals orientation using 260 computed tomography scans of extant humans (Homo sapiens), bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). Humans and bonobos proved more similarities between themselves than with chimpanzees. This finding did not fit with the well established chimpanzee - bonobo monophyly. One hypothesis was convergent evolution in which bonobos and humans produce independently similar phenotypes possibly in response to similar selective pressures that may be associated with postural adaptations. Another possibility was convergence following a "random walk" (Brownian motion) evolutionary model. A more parsimonious explanation was that the bonobo-human labyrinthine shared morphology more closely retained the ancestral condition with chimpanzees being subsequently derived. Finally, these results might be a consequence of genetic diversity and incomplete lineage sorting. The remarkable symmetry of the Semicircular Canals was the second major finding of this article with possible applications in taphonomy. It has the potential to investigate altered fossils, inferring the probability of post-mortem deformation which can lead to difficulties in understanding taxonomic variation, phylogenetic relationships, and functional morphology.