Developments in development: What have we learned from primate locomotor ontogeny?
*allometry; *gait mechanics; *life history; *locomotor independence; *ontogeny; Animals; Anthropology; Biomechanical Phenomena/*physiology; Bone and Bones/physiology; Female; Gait/*physiology; Hand Strength/physiology; Humans; Locomotion/*physiology; Male; Phylogeny; Physical; Primates/*physiology
The importance of locomotion to evolutionary fitness has led to extensive study of primate locomotor behavior, morphology and ecology. Most previous research has focused on adult primates, but in the last few decades, increased attention to locomotor development has provided new insights toward our broader understanding of primate adaptation and evolution. Here, we review the contributions of this body of work from three basic perspectives. First, we assess possible determinants on the timing of locomotor independence, an important life history event. Significant influences on timing of locomotor independence include adult female body mass, age at weaning, and especially relative brain size, a significant predictor of other primate life history variables. Additionally, we found significant phylogenetic differences in the timing of locomotor independence, even accounting for these influences. Second, we discuss how structural aspects of primate growth may enhance the locomotor performance and safety of young primates, despite their inherent neuromotor and musculoskeletal limitations. For example, compared to adults, growing primates have greater muscle mechanical advantage, greater bone robusticity, and larger extremities with relatively long digits. Third, focusing on primate quadrupedalism, we provide examples that illustrate how ontogenetic transitions in morphology and locomotion can serve as a model system for testing broader principles underlying primate locomotor biomechanics. This approach has led to a better understanding of the key features that contribute to primates' stride characteristics, gait patterns, limb force distribution, and limb postures. We have learned a great deal from the study of locomotor ontogeny, but there is much left to explore. We conclude by offering guidelines for future research, both in the laboratory and the field.
Young Jesse W; Shapiro Liza J
American journal of physical anthropology
2018
2018-01
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ajpa.23388" target="_blank" rel="noreferrer noopener">10.1002/ajpa.23388</a>
Grasping primate development: Ontogeny of intrinsic hand and foot proportions in capuchin monkeys (Cebus albifrons and Sapajus apella).
*growth; *life history; *phalangeal index; *scaling; Animals; Anthropology; Cebus/*anatomy & histology/physiology; Female; Finger Phalanges/*anatomy & histology/diagnostic imaging/physiology; Foot/*anatomy & histology/diagnostic imaging/physiology; Hand Strength/*physiology; Hand/*anatomy & histology/diagnostic imaging/physiology; Linear Models; Physical; Pregnancy; Toe Phalanges/*anatomy & histology/diagnostic imaging/physiology
Young primates have relatively large hands and feet for their body size, perhaps enhancing grasping ability. We test the hypothesis that selection for improved grasping ability is responsible for these scaling trends by examining the ontogeny of intrinsic hand and foot proportions in capuchin monkeys (Cebus albifrons and Sapajus apella). If selection for improved grasping ability is responsible for the observed patterns of hand and foot growth in primates, we predicted that fingers and toes would be longer early in life and proportionally decline with age. We measured the lengths of manual and pedal metapodials and phalanges in a mixed-longitudinal radiographic sample. Bone lengths were (a) converted into phalangeal indices (summed non-distal phalangeal length/metapodial length) to test for age-related changes in intrinsic proportions and (b) fit to Gompertz models of growth to test for differences in the dynamics of phalangeal versus metapodial growth. Manual and pedal phalangeal indices nearly universally decreased with age in capuchin monkeys. Growth curve analyses revealed that metapodials generally grew at a faster rate, and for a longer duration, than corresponding phalanges. Our findings are consistent with the hypothesis that primates are under selection for increased grasping ability early in life. Relatively long digits may be functionally adaptive for growing capuchins, permitting a more secure grasp on both caregivers and arboreal supports, as well as facilitating early foraging. Additional studies of primates and other mammals, as well as tests of grasping performance, are required to fully evaluate the adaptive significance of primate hand and foot growth.
Young Jesse W; Heard-Booth Amber N
American journal of physical anthropology
2016
2016-09
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/ajpa.23013" target="_blank" rel="noreferrer noopener">10.1002/ajpa.23013</a>