Relative growth of the limbs and trunk in the African apes

TLDR

Understanding relative growth and allometry in African apes is crucial, as reliable ontogenetic data require subadult examination and suggest that leg length decreases with body size to preserve locomotor abilities. The study compares ontogenetic relative growth patterns of postcranial dimensions and interspecific proportion differences among *Pan paniscus*, *Pan troglodytes*, and *Gorilla gorilla*. The study finds that while some postcranial growth patterns are similar across the three species, others differ markedly, and bonobo limbs are relatively longer than those of the common chimpanzee or gorilla, resembling a primitive condition.

Abstract

Abstract Examination of relative growth and allometry is important for our understanding of the African apes, as they represent a closely related group of species of increasing body size. This study presents a comparison of ontogenetic relative growth patterns of some postcranial dimensions in Pan paniscus, Pantroglodytes , and Gorilla gorilla. Interspecific proportion differences among the three species are also analyzed. It is stressed that reliable ontogenetic information can only be obtained if subadults are examined‐growth data cannot be inferred from static adult scaling. Results indicate that some postcranial relative growth patterns are very similar in the three species, suggesting differential extrapolation of a common growth pattern, whereas for other proportion comparisons the growth trends differ markedly among the species, producing distinct shape differences in the adults Interspecific shape changes among the three species are characterized by positive allometry of chest girth and negative allometry of body height and leg length. It is suggested that relative decrease of leg length with increasing body size among the African pongids might be expected on biomechanical grounds, in order to maintain similar locomotor abilities of climbing arborealism and quadrupedal terrestrialism. Relative to body weight or trunk length, the limbs of the bonobo (Pan paniscus) are longer than in the common chimpanzee or the gorilla, with a lower intermembral index. This may most closely resemble the primitive condition for the African apes.