Relative growth and shape of the locomotor skeleton in lesser apes

Jungers, William L.; Cole, Maria S.

doi:10.1016/0047-2484(92)90045-b

Cited by 35 publications

(22 citation statements)

References 26 publications

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“…We conducted analyses at the generic level for hominoids; therefore, the group Hylobates consists of H. lar and H. syndactylus in the present study. This is not unreasonable because the clavicular length of adult Hylobates syndactylus lies on the extrapolation of an ontogenetic trend of H. lar, according to Jungers and Cole (1992). The specimens are housed in the Anthropological Institute, University of Zürich; The Bavarian State Collection of Zoology, München; Japan Monkey Centre, Inuyama; and Primate Research Institute, Kyoto University.…”

Section: Methodsmentioning

confidence: 99%

Is the Clavicle of Apes Long? An Investigation of Clavicular Length in Relation to Body Mass and Upper Thoracic Width

2010

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An elongated clavicle is one of the distinct features of apes and humans. It plays an important role in providing mobility as well as stability for the shoulder joints. The relative length of the clavicle is an especially important factor in limiting the range of shoulder joint excursion. It is said that among primates, Asian apes, i.e., gibbons and orang-utans, have very long clavicles. At the same time, they also have a wide upper thoracic cage, which may diminish the effective length of the clavicle. To clarify the length of the clavicle in apes, from the standpoint of the functional anatomy of the shoulder girdle, we examined clavicular length in 15 anthropoid species exhibiting various positional behaviors. The results confirm that clavicle length in Asian apes is long, and chimpanzees have a short clavicle like that of Old and New World monkeys, when scaled to body mass. The clavicular length of chimpanzees, however, is intermediate between Old World monkeys and Asian apes when scaled against thoracic width. Therefore, living apes can be grouped together, albeit just barely, by possession of a relatively long clavicle for their thoracic cage size. Interestingly, New World monkeys tend to exhibit a longer clavicle than Old World monkeys of equivalent body mass or thoracic cage width. Although it is unclear whether the ancestral condition of clavicular length in anthropoids was similar to that of living Old or New World monkeys, an elongation of clavicle was an important step toward evolution of the modern body plan of hominoids.

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Section: Methodsmentioning

confidence: 99%

Is the Clavicle of Apes Long? An Investigation of Clavicular Length in Relation to Body Mass and Upper Thoracic Width

2010

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“…Many previous studies described the evolution of dimorphism for specific ape species (e.g., Galdikas, 1979;MacKinnon, 1979;Rodman, 1973;Rodman and Ritani, 1987;Jungers and Cole, 1992;Masterson and Leutenegger, 1992;Leutenegger and Masterson, 1989). Comparative ontogenetic data indicate that different mechanisms might underlie similar degrees of adult dimorphism (e.g., Fedigan, 1982;Leigh, 1995;Leigh and Shea, 1995;Shea, 1986).…”

Section: Ontogeny and Dimorphismmentioning

confidence: 96%

Ontogeny of canine dimorphism in extant hominoids

Schwartz

Dean

2001

American J Phys Anthropol

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Many behavioral and ecological factors influence the degree of expression of canine dimorphism for different reasons. Regardless of its socioecological importance, we know virtually nothing about the processes responsible for the development of canine dimorphism. Our aim here is to describe the developmental process(es) regulating canine dimorphism in extant hominoids, using histological markers of tooth growth. Teeth preserve a permanent record of their ontogeny in the form of short- and long-period incremental markings in both enamel and dentine. We selected 52 histological sections of sexed hominoid canine teeth from a total sample of 115, from which we calculated the time and rate of cuspal enamel formation and the rate at which ameloblasts differentiate along the future enamel-dentine junction (EDJ) to the end of crown formation. Thus, we were able to reconstruct longitudinal growth curves for height attainment in male and female hominoid canines. Male hominoids consistently take longer to form canine crowns than do females (although not significantly so for our sample of Homo). Male orangutans and gorillas occasionally take up to twice as long as females to complete enamel formation. The mean ranges of female canine crown formation times are similar in Pan, Gorilla, and Pongo. Interspecific differences between female Pan canine crown heights and those of Gorilla and Pongo, which are taller, result from differences in rates of growth. Differences in canine crown heights between male Pan and the taller, more dimorphic male Gorilla and Pongo canines result both from differences in total time taken to form enamel and from faster rates of growth in Gorilla and Pongo. Although modern human canines do not emerge as significantly dimorphic in this study, it is well-known that sexual dimorphism in canine crown height exists. Larger samples of sexed modern human canines are therefore needed to identify clearly what underlies this.

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“…However, there is no reason to expect every aspect of forelimb morphology and ontogeny to be identical in Pan and Gorilla for knuckle-walking to be homologous. Brachiation and suspension are almost certainly homologous in siamangs and lar gibbons, and yet the relative growth of their locomotor skeletons are substantially different (Jungers and Cole, 1992). Australopithecines and modern humans have fundamental differences in adult lower limb design, and grew very differently, in terms of rate, duration, and pattern within the skeleton (Bromage, 1987;Dean et al, 1993;Tardieu, 1999).…”

Section: Knuckle-walking Ancestormentioning

confidence: 99%

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Richmond

Begun

Strait

2001

Am. J. Phys. Anthropol.

116

191

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Some of the most long-standing questions in paleoanthropology concern how and why human bipedalism evolved. Over the last century, many hypotheses have been offered on the mode of locomotion from which bipedalism originated. Candidate ancestral adaptations include monkey-like arboreal or terrestrial quadrupedalism, gibbon-or orangutan-like (or other forms of) climbing and suspension, and knuckle-walking. This paper reviews the history of these hypotheses, outlines their predictions, and assesses them in light of current phylogenetic, comparative anatomical, and fossil evidence. The functional significance of characteristics of the shoulder and arm, elbow, wrist, and hand shared by African apes and humans, including their fossil relatives, most strongly supports the knuckle-walking hypothesis, which reconstructs the ancestor as being adapted to knuckle-walking and arboreal climbing. Future fossil discoveries, and a clear understanding of anthropoid locomotor anatomy, are required to ultimately test these hypotheses. If knucklewalking was an important component of the behavioral repertoire of the prebipedal human ancestor, then we can reject scenarios on the origin of bipedalism that rely on a strictly arboreal ancestor. Moreover, paleoenvironmental data associated with the earliest hominins, and their close relatives, contradict hypotheses that place the agents of selection for bipedality in open savanna habitats. Existing hypotheses must explain why bipedalism would evolve from an ancestor that was already partly terrestrial. Many food acquisition and carrying hypotheses remain tenable in light of current evidence.

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Relative growth and shape of the locomotor skeleton in lesser apes

Cited by 35 publications

References 26 publications

Is the Clavicle of Apes Long? An Investigation of Clavicular Length in Relation to Body Mass and Upper Thoracic Width

Is the Clavicle of Apes Long? An Investigation of Clavicular Length in Relation to Body Mass and Upper Thoracic Width

Ontogeny of canine dimorphism in extant hominoids

Origin of human bipedalism: The knuckle-walking hypothesis revisited

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