African apes and the evolutionary history of orthogrady and bipedalism

Williams, Scott A.; Prang, Thomas C.; Russo, Gabrielle A.; Young, Nathan M.; Gebo, Daniel L.

doi:10.1002/ajpa.24684

Cited by 8 publications

(3 citation statements)

References 317 publications

(690 reference statements)

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“…Primates exhibit an important intertaxic locomotor diversity, which is reflected not only in the variable anatomy of their limbs but also in some particularities in the rest of their skeleton (Almécija et al, 2021; Fleagle, 2013; Williams et al, 2023). Given that the ribcage and the lumbar spine are the nexus between the shoulder and pelvic girdles, their configuration is highly related to the mode of locomotion in this group (Fleagle & Lieberman, 2021).…”

Section: Introductionmentioning

confidence: 99%

Covariation between the shape and mineralized tissues of the rib cross section in Homo sapiens, Pan troglodytes and Sts 14

López‐Rey,

Cambra‐Moo,

González Martín

et al. 2023

American Journal of Biological Anthropology

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ObjectivesStudying rib torsion is crucial for understanding the evolution of the hominid ribcage. Interestingly, there are variables of the rib cross section that could be associated with rib torsion and, consequently, with the morphology of the thorax. The aim of this research is to conduct a comparative study of the shape and mineralized tissues of the rib cross section in different hominids to test for significant differences and, if possible, associate them to different thoracic morphotypes.Materials and MethodsThe sample consists of the rib cross sections at the midshaft taken from 10 Homo sapiens and 10 Pan troglodytes adult individuals, as well as from A. africanus Sts 14. The shape of these rib cross sections was quantified using geometric morphometrics, while the mineralized tissues were evaluated using the compartmentalization index. Subsequently, covariation between both parameters was tested by a Spearman's ρ test, a permutation test and a linear regression.ResultsGenerally, P. troglodytes individuals exhibit rib cross sections that are rounder and more mineralized compared to those of H. sapiens. However, the covariation between both parameters was only observed in typical ribs (levels 3–10). Although covariation was not found in the rib cross sections of Sts 14, their parameters are closer to P. troglodytes.DiscussionOn the one hand, the differences observed in the rib cross sections between H. sapiens and P. troglodytes might be related to different degrees of rib torsion and, consequently, to different thoracic 3D configurations. These findings can be functionally explained by considering their distinct modes of breathing and locomotion. On the other hand, although the rib cross sections belonging to Sts 14 are more similar to those of P. troglodytes, previous publications determined that their overall morphology is closer to modern humans. This discrepancy could reflect a diversity of post‐cranial adaptations in Australopithecus.

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Section: Introductionmentioning

confidence: 99%

Covariation between the shape and mineralized tissues of the rib cross section in Homo sapiens, Pan troglodytes and Sts 14

López‐Rey,

Cambra‐Moo,

González Martín

et al. 2023

American Journal of Biological Anthropology

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“…The large body size of most apes, relative to monkeys and other primates, is expected to substantially increase the energetic costs of vertical climbing [17] and risk of falling [18], and it is long hypothesized that the morphologies of hominoid shoulders and elbows evolved to mitigate these twin challenges [19][20][21][22]. The retention of these same forelimb traits across early hominin taxa is another topic of enduring debate [23], in part because it suggests that vertical climbing was an essential preadaptation for obligate bipedalism [24][25][26][27][28][29][30] (but see [31]).…”

Section: Introductionmentioning

confidence: 99%

Downclimbing and the evolution of ape forelimb morphologies

Fannin,

Joy,

Dominy

et al. 2023

R. Soc. open sci.

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The forelimbs of hominoid primates (apes) are decidedly more flexible than those of monkeys, especially at the shoulder, elbow and wrist joints. It is tempting to link the greater mobility of these joints to the functional demands of vertical climbing and below-branch suspension, but field-based kinematic studies have found few differences between chimpanzees and monkeys when comparing forelimb excursion angles during vertical ascent (upclimbing). There is, however, a strong theoretical argument for focusing instead on vertical descent (downclimbing), which motivated us to quantify the effects of climbing directionality on the forelimb kinematics of wild chimpanzees ( Pan troglodytes ) and sooty mangabeys ( Cercocebus atys ). We found that the shoulders and elbows of chimpanzees and sooty mangabeys subtended larger joint angles during bouts of downclimbing, and that the magnitude of this difference was greatest among chimpanzees. Our results cast new light on the functional importance of downclimbing, while also burnishing functional hypotheses that emphasize the role of vertical climbing during the evolution of apes, including the human lineage.

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“…Reading this, one might think that hominin‐like bipedalism is an inevitable outcome of the Miocene ape radiation. However, orthogenesis (goal‐oriented evolution) is a disproven pre‐Darwinian concept: not all Miocene apes were orthograde and certainly not all orthograde apes were—or currently are—adapted to bipedalism (see Williams et al 6 for a review). For example, “spinal lordosis” is cited as evidence for bipedalism in Oreopithecus (p. 62), but that hypothesis was tested and soundly rejected 4 …”

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confidence: 99%

The wrong ape for early human origins: A skewed view of paleoanthropology and evolutionary theoryM.Kay MartinThe wrong ape for early human origins: The chimpanzee as a skewed ancestral modelLanham, MD: Lexington Books. ISBN: 9781666923872.

African apes and the evolutionary history of orthogrady and bipedalism

Cited by 8 publications

References 317 publications

Covariation between the shape and mineralized tissues of the rib cross section in Homo sapiens, Pan troglodytes and Sts 14

Covariation between the shape and mineralized tissues of the rib cross section in Homo sapiens, Pan troglodytes and Sts 14

Downclimbing and the evolution of ape forelimb morphologies

The wrong ape for early human origins: A skewed view of paleoanthropology and evolutionary theoryM.Kay MartinThe wrong ape for early human origins: The chimpanzee as a skewed ancestral modelLanham, MD: Lexington Books. ISBN: 9781666923872.

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