Ontogeny of knuckle-walking hand postures in African apes

Inouye, Sandra E.

doi:10.1006/jhev.1994.1028

Cited by 94 publications

(89 citation statements)

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“…Previous researchers have noted postural (16,31,32) and biomechanical (13,14) differences in knuckle-walking behavior among African apes and our hypothesis expands upon this foundation of work to suggest that knuckle-walking is a fundamentally different mode of locomotion in Pan and Gorilla. This hypothesis is supported by existing African ape locomotor data (17,(27)(28)(29)(30)(31)(32)(33)(34)(35). As with other forms of locomotion, limb posture has a profound influence the load experienced by the wrist and digits in a knuckle-walking animal.…”

Section: Resultssupporting

confidence: 75%

“…Previously researchers have always treated knuckle-walking in Pan and Gorilla as a unified biomechanical phenomenon (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(16)(17)(18)(19). This assumption persists despite well-known variation in substrate use among African apes (27)(28)(29)(30), as well as known differences in hand posture across species (16,31,32) and substrates (33). When considered without respect to important confounding variables like substrate and hand posture, variation in morphology across species of knuckle-walking apes is difficult to interpret and leads to overly complex evolutionary scenarios.…”

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confidence: 99%

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Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor

Kivell

Schmitt

2009

Proc. Natl. Acad. Sci. U.S.A.

162

129

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Despite decades of debate, it remains unclear whether human bipedalism evolved from a terrestrial knuckle-walking ancestor or from a more generalized, arboreal ape ancestor. Proponents of the knuckle-walking hypothesis focused on the wrist and hand to find morphological evidence of this behavior in the human fossil record. These studies, however, have not examined variation or development of purported knuckle-walking features in apes or other primates, data that are critical to resolution of this long-standing debate. Here we present novel data on the frequency and development of putative knuckle-walking features of the wrist in apes and monkeys. We use these data to test the hypothesis that all knuckle-walking apes share similar anatomical features and that these features can be used to reliably infer locomotor behavior in our extinct ancestors. Contrary to previous expectations, features long-assumed to indicate knuckle-walking behavior are not found in all African apes, show different developmental patterns across species, and are found in nonknuckle-walking primates as well. However, variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla). The presence of purported knuckle-walking features in the hominin wrist can thus be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor occupying the ecological niche common to all living apes.ince Darwin first discussed pathways of human evolution in The Descent of Man, there has been an ongoing and often rancorous debate over the nature of locomotion in our prebipedal human ancestor. The debate can be summarized with 2 competing models. One model envisions the prehuman ancestor as a terrestrial knuckle-walker, a behavior frequently used by our closest living relatives, the African apes (1-6). In the alternative model, early human bipedalism is seen as having evolved from a more generalized arboreal, climbing-oriented ancestor, a mode of locomotion that is used by all living apes (7-10). Each scenario has important and profoundly different implications for understanding the evolution of ape and human locomotion.If early human bipedalism evolved from an arboreal ancestor, current ape-human phylogeny showing chimpanzees and bonobos as the sister taxa of humans (supporting information (SI) Fig. S1) logically implies that knuckle-walking evolved independently in both African ape lineages (Gorilla and Pan). In contrast, proponents of a terrestrial knuckle-walking hypothesis of human locomotor evolution hypothesize that African apes and humans share a common knuckle-walking ancestor. Advocates for this model support their claims by arguing that there are specific morphological features, particularly of the wrist and hand, that refle...

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Section: Resultssupporting

confidence: 75%

mentioning

confidence: 99%

Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor

Kivell

Schmitt

2009

Proc. Natl. Acad. Sci. U.S.A.

162

129

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“…The strongest evidence of Straus (1949) came from the anatomical 2 Knuckle-walking features that have been noted as absent in Australopithecus (e.g., dorsal ridge on metacarpal head), and thus might be considered "lost" in this scenario, are not suitable characters for cladistic analyses for a variety of reasons. Metacarpal head knucklewalking features are often not present in African apes (Susman and Creel, 1979;Shea and Inouye, 1993;Inouye, 1994b), and their expression may be influenced by body mass and epigenetic factors during growth (Inouye, 1994b;Richmond and Strait, 2000;Lovejoy et al, 2001). similarities in the hands of modern humans and arboreal quadrupeds (e.g., macaques).…”

Section: Arboreal Quadruped Ancestormentioning

confidence: 99%

“…) habilis (Susman and Stern, 1979). However, it is generally acknowledged that the absence of the metacarpal features in hominins does not rule out a knuckle-walking ancestry, because these features are often not present in extant knuckle-walkers (Susman and Creel, 1979;Shea and Inouye, 1993;Inouye, 1994b), and because these taxa postdate the origins of bipedalism by a substantial period of time in which traces of ancestral adaptations may disappear (Stern and Susman, 1983). The presence of the metacarpal head traits may be size-related, as they are best expressed in gorillas, but are quite variable in common chimpanzees and bonobos.…”

Section: Climbing (Antipronograde) Ancestormentioning

confidence: 99%

“…More likely causes of the differences in Africanape carpal development include general growth difference in body mass (Leigh and Shea, 1996) and the kinematic differences in knuckle-walking between the African apes (Inouye, 1994a;Dainton and Macho, 1999). Kinematic differences in knuckle-walking may be related to specialization in gorillas for knuckle-walking at large body size as adults and/or, as Inouye (1994b) notes, differences in locomotor repertoire such as a greater emphasis on arboreality Fig.…”

Section: Knuckle-walking Ancestormentioning

confidence: 99%

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Origin of human bipedalism: The knuckle-walking hypothesis revisited

Richmond

Begun

Strait

2001

Am. J. Phys. Anthropol.

223

164

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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, ontogeny, and sexual dimorphism ingorilla(Gorilla gorilla gorilla andG. g. beringei): Evolutionary and ecological considerations

Taylor

1997

Am. J. Primatol.

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Gorillas are the largest and among the most sexually dimorphic of all extant primates. While gorillas have been incorporated in broad‐level comparisons among large‐bodied hominoids or in studies of the African apes, comparisons between gorilla subspecies have been rare. During the past decade, however, behavioral, morphological, and molecular data from a number of studies have indicated that the western lowland (Gorilla gorilla gorilla) and eastern mountain (Gorilla gorilla beringei) subspecies differ to a greater extent than has been previously believed. In this study I compare patterns of relative growth of the postcranial skeleton to evaluate whether differences between subspecies result from the differential extension of common patterns of relative growth. In addition, patterns of ontogeny and sexual dimorphism are also examined. Linear skeletal dimensions and skeletal weight were obtained for ontogenetic series of male and female G.g. gorilla (n = 315) and G.g. beringei (n = 38). Bivariate and multivariate methods of analysis were used to test for differences in patterns of relative growth, ontogeny, and sexual dimorphism between sexes of each subspecies and in same‐sex comparisons between subspecies. Results indicate males and females of both subspecies are ontogenetically scaled for postcranial proportions and that females undergo an earlier skeletal growth spurt compared to males. However, results also indicate that the onset of the female growth spurt occurs at different dental stages in lowland and mountain gorillas and that mountain gorillas may be characterized by higher rates of growth. Finally, data demonstrate lowland and mountain gorilla females do not differ significantly in adult body size, but mountain gorilla males are significantly larger than lowland gorilla males, suggesting mountain gorillas are characterized by a higher degree of sexual dimorphism in body size. Thus, although lowland and mountain gorillas do not appear to have evolved novel adaptations of the postcranium which correlate with differences in locomotor behavior, the present investigation establishes subspecies differences in ontogeny and sexual dimorphism which may be linked with ecological variation. Specifically, these findings are evaluated in the context of risk aversion models which predict higher growth rates and increased levels of sexual dimorphism in extreme folivores. Am. J. Primatol. 43:1–31, 1997. © 1997 Wiley‐Liss, Inc.

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Ontogeny of knuckle-walking hand postures in African apes

Cited by 94 publications

References 0 publications

Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor

Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor

Origin of human bipedalism: The knuckle-walking hypothesis revisited

Relative growth, ontogeny, and sexual dimorphism ingorilla(Gorilla gorilla gorilla andG. g. beringei): Evolutionary and ecological considerations

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