The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Postnatal growth of the long bones in the African apes

ANDREW GALLAGHER.

School of Anatomical Sciences, University of the Witwatersrand

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The in-utero emergence of distinctive limb-to-trunk and intra-limb proportions of Gorilla, Pan, and Homo, were detailed by A.H. Schultz in a series of contributions in the 1920’s. On the basis of Schultz’s data, it is probable that the observed differences in proportions in human and ape foetuses are established during initial chrondrogenesis and emergence of the hyaline cartilage template, primarily ossified in the region of the diaphyseal centre. By birth, the elongation of the upper limb in Gorilla/Pan and lower limb in humans is apparent, yet it remains unclear the extent to which allometric growth of the osseous elements of the limbs is accelerated during early postnatal ontogeny. Published data (Fazekas and Kosa, 1978) and additional specimens yield an allometric baseline for the assessment of comparative post-natal ontogenetic growth in humans and extant African apes. Linear regression models were developed for the proportional growth in-utero of dependent skeletal dimensions against a valid proxy of general size, the mean of five log-transformed variates. In humans, foetal growth of the humerus and radius is isometric, whereas the lower limb attests significant positive allometry. Surprising consistency exists in the post-natal ontogenetic trajectories of the appendicular skeleton in humans and the derived foetal allometric functions, with the exception of the femur and tibia, which depart from the foetal trajectory in early postnatal life. Postnatal growth of the zeugopoda evidence positive allometry in Gorilla and Pan, whereas sylopoda are approximately isometric, and this explains observed discrepancies in brachial indices of adult Gorilla and Pan.

Financial support was received from the Faculty of Health Sciences, University of the Witwatersrand, the Palaeontology Scientific Trust (PAST), the Faculty of Humanities,UniversityofJohannesburg, the National Research Foundation (RSA), and the Ford Foundation.

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