Nonhuman Primate Locomotion

Abstract

| I N TR ODU C TI ONAs an arboreal radiation of mammals, primates 1 have access to a rich set of resources including fruits, seeds, flowers, leaves, insects and the occasional lizard. To reach them they must navigate narrow diameter, discontinuous supports that are oriented at angles ranging from horizontal to vertical, and do so by engaging in a wide variety of locomotor behaviors. In addition to the quadrupedal walking, running and bounding commonly observed among non-marine mammals, primates occasionally walk bipedally, display jumping, leaping, and hopping behaviors, suspend themselves from their forelimbs, hind limbs, as well as all four limbs, climb up and down vertical and inclined supports, utilize cantilevered bridging between supports, and engage in a variety of nonstereotypical limb motions in order to scramble along small branches/ lianas etc. Occupying an arboreal habitat, however, doesn't necessarily lead to the diversity in locomotor behaviors observed among primates.A variety of other mammals like many rodents, carnivores, scandentians and marsupials also live in the trees but retain basic quadrupedal walking, running, and bounding habits. The difference appears to be that while other mammals rely on claws to interlock with tree bark to avoid falling, primates encircle narrow arboreal substrates with grasping hands and feet tipped with flattened nails rather than claws. When, how and why primates developed a dependence on grasping clawless extremities is a matter of continuing debate, but arguably underlies much of the locomotor diversity observed in the primate Order. Much of the research establishing these generalization has appeared in the pages of the American Journal of Physical Anthropology (AJPA) and in this review I will attempt to trace the development of many of these ideas. | E A RL Y H I STOR YMost of the research published in the early issues of the AJPA was on the attributes of modern human populations including the identification of the origins and interrelationships of different "races" across the world. There was little mention of nonhuman primates in the issues of AJPA from the 1920s other than in the context of understanding the origins of our species. Then as is the case now, analysis and interpretation of fossil material began with comparisons to our "simian" relations, often with the viewpoint of an evolutionary progression beginning with primitive lemurs and culminating in the appearance of human beings.This perspective meant that the course of human evolution could be studied through comparative anatomy, as Dudley Morton attempted to do through a series of comparative studies on human foot evolution (Morton, 1922(Morton, , 1924(Morton, , 1927. Although it is often said that early theories about human evolution emphasized brain size and tool use, on the basis of his research on the foot, Morton concluded that, "The course of human evolution was evidently characterized by progressive adaptations for erect terrestrial bipedism [sic], showing first in the feet and gradually ext...

Locomotion, posture, and the foramen magnum in primates: Reliability of indices and insights into hominin bipedalism

“…locomotor plasticity (Larson, 2018). Nevertheless, the multivariate pairwise test between groups (Table 3) overturns the situation depicted in the PCA and no significant difference is observed across most locomotor groups.…”

Positional Behaviours of François’ Langur (Trachypithecus francoisi) in the Limestone Forest of Nonggang, Guangxi, South-West China

“…Studies of positional behaviour are relevant for understanding how animals move through their environments, access food, avoid predation and locate mates [Cant, 1992;Blanchard et al, 2015;Larson, 2018]. Because primates inhabit various environments and often face dramatic seasonal and ecological variation [Richard, 1985], positional behaviour adjustments are one way they cope with changes in food availability [Youlatos, 1998], thermoregulation demand [Dasilva, 1993] and forest structure alteration [Gebo and Chapman, 1995a].…”

Rapid evolution of the primate larynx?

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