Locomotor Anatomy and Behaviour in Olive Baboons: Integrative Analysis from Early Infancy to Autonomy
10 March 2017
Campus Drie Eiken, Promotiezaal Q0.02 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Biology
Peter Aerts & Gilles Berillon
PhD defence François Druelle - Faculty of Science - Department of Biology
The diversity of the environments in which baboons live demands specific locomotor activities (e.g. endurance walking, cliff climbing, etc.). Hence locomotor capacities and the development thereof are key to their survival. To improve our understanding of these performances and how these relate to morphology and behaviour we studied the transition from the onset of independent foraging to autonomy. We conducted a longitudinal and cross-sectional follow-up of olive baboons living in captivity at the Primatology Station of the CNRS in France. We studied, in parallel, the morphometrics, the temporal kinematics and the positional behaviour.
First, our results show that the proportion of quadrupedal walking gradually increases on the expense of grasping behaviours during infancy. We observed that this pattern is highly correlated to changes in the body mass distribution, mainly at the level of the limbs where mass shifts proximally. While a more distal limb mass distribution reflects important grasping capacity for clinging onto the mother’s fur, more proximal masses into the limbs are adaptive for reducing energy consumption during quadrupedal locomotion.
Second, our results show that the ontogenetic changes in the pattern of body mass distribution facilitate occasional spontaneous bipedal walking in juveniles and adults in terms of bout duration, i.e. in individuals that possess a lighter head on a heavier trunk show longer bipedal bouts.
Third, during the early period of development, young baboons improve their interlimb coordination in quadrupedal walking. We found that the intrinsic morpho-dynamics of fore- and hind limbs (at the level of the convergence of the natural pendular period) have a significant and positive impact on this interlimb coordination pattern, thus probably facilitating, very early in development, the motor control and learning of quadrupedal walking. Finally, we observed an improvement of the coordination of the hind limbs when walking bipedally, coinciding to the development of interlimb coordination in quadrupedal walking. Hence, improvement of quadrupedal locomotor capacity does not exclude the development of bipedal behaviours, despite bipedal experiences remain rare in the ontogeny of baboons (<0.5%). This is also observed during chimpanzee ontogeny and, therefore, sheds light on the emergence of new locomotor modes during the evolution of primates.
Indeed, these results suggest a similar basic control mechanism in bipedal and quadrupedal locomotion. From an evolutionary perspective, we propose that secondary locomotor modes, such as bipedalism, experienced during infancy as by-products of locomotor development may lead to evolutionary novelties when under appropriate selective pressures.