Morphological variation of the maxilla in modern humans and African apes

Hanegraef, Hester; David, Romain; Spoor, Fred

doi:10.1016/j.jhevol.2022.103210

Cited by 3 publications

(2 citation statements)

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“…The measurement protocol follows Hanegraef et al. ( 2022 ), with the size and shape of the maxillae captured by 68 3D landmarks (Table 2 ; Figure 1 ) that were placed on the surfaces and recorded using Avizo 7.1. These landmarks capture the relative position and size of the dental alveoli from the first incisor to the second molar, the midplane palate and subnasal area, the zygomatic root, and the inferior region of the nasal and orbital margins.…”

Section: Methodsmentioning

confidence: 99%

“…A principal component analysis (PCA) was performed to examine maxillary shape differences between wild and captive individuals (question 1), and statistical significance was tested through multivariate regression (shape ~ group). Shape differences between captive and wild chimpanzees were visualised and then compared by superimposing their mean maxillary shapes, minimising the distance between postcanine alveolar landmarks as the most efficient way to characterise distinct morphologies (Hanegraef et al., 2022 ). Moreover, we obtained absolute and relative dimensions of the dental alveoli, averaging the left and right sides for each specimen, and statistical significance of differences between the wild and captive samples was examined with two‐sample t‐tests.…”

Section: Methodsmentioning

confidence: 99%

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Maxillary morphology of chimpanzees: Captive versus wild environments

Hanegraef,

Spoor

2024

Journal of Anatomy

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Morphological studies typically avoid using osteological samples that derive from captive animals because it is assumed that their morphology is not representative of wild populations. Rearing environments indeed differ between wild and captive individuals. For example, mechanical properties of the diets provided to captive animals can be drastically different from the food present in their natural habitats, which could impact cranial morphology and dental health. Here, we examine morphological differences in the maxillae of wild versus captive chimpanzees (Pan troglodytes) given the prominence of this species in comparative samples used in human evolution research and the key role of the maxilla in such studies. Size and shape were analysed using three‐dimensional geometric morphometric methods based on computed tomography scans of 94 wild and 30 captive specimens. Captive individuals have on average larger and more asymmetrical maxillae than wild chimpanzees, and significant differences are present in their maxillary shapes. A large proportion of these shape differences are attributable to static allometry, but wild and captive specimens still differ significantly from each other after allometric size adjustment of the shape data. Levels of shape variation are higher in the captive group, while the degree of size variation is likely similar in our two samples. Results are discussed in the context of ontogenetic growth trajectories, changes in dietary texture, an altered social environment, and generational differences. Additionally, sample simulations show that size and shape differences between chimpanzees and bonobos (Pan paniscus) are exaggerated when part of the wild sample is replaced with captive chimpanzees. Overall, this study confirms that maxillae of captive chimpanzees should not be included in morphological or taxonomic analyses when the objective is to characterise the species.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Maxillary morphology of chimpanzees: Captive versus wild environments

Hanegraef,

Spoor

2024

Journal of Anatomy

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Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene

Antón

Middleton

2023

Journal of Human Evolution

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Mid-Pliocene hominin diversity revisited

HANEGRAEF,

LEAKEY,

LEAKEY

et al. 2024

Comptes Rendus Palevol

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Geometric morphometric analyses are used to examine the maxillary shape of the Kenyanthropus platyops Leakey, Spoor, Brown, Gathogo, Kiarie, Leakey & McDougall, 2001 holotype KNM-WT 40000 and the Australopithecus deyiremeda Haile-Selassie, Gilbert, Melillo, Ryan, Alene, Deino, Levin, Scott & Saylor, 2015 holotype BRT-VP-3/1, expanding on the work of Spoor et al. (2010, 2016) by using more accurate data and a larger comparative sample. The main objective is to assess whether these two specimens differ from the contemporary taxon Australopithecus afarensis Johanson, White & Coppens, 1978 and more broadly from species of Australopithecus Dart, 1925 and Paranthropus Broom, 1938, as well as from each other. Five two-dimensional landmarks recorded on virtual models obtained from computed tomography scans quantify key features of the maxilla used in the differential diagnoses of K. platyops and A. deyiremeda. Principal component analyses were performed to describe shape differences, and the magnitudes of these differences and their statistical significance were assessed using Procrustes and Mahalanobis distances, respectively. The maxillary shapes of both KNM-WT 40000 and BRT-VP-3/1 are significantly different from A. afarensis, the former more so than the latter, and they differ from A. afarensis in dissimilar ways. Where KNM-WT 40000 has a more anterosuperiorly positioned zygomatic process with a longer, more orthognathic, and transversely flat subnasal clivus than A. afarensis, the shape difference of BRT-VP-3/1 is best described as a posterior shift (retraction) of the entire dental arcade. The findings of this study quantitatively support the species status of K. platyops and A. deyiremeda, and corroborate the notion that hominin diversity extended well into the mid-Pliocene of eastern Africa.

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Morphological variation of the maxilla in modern humans and African apes

Cited by 3 publications

References 132 publications

Maxillary morphology of chimpanzees: Captive versus wild environments

Maxillary morphology of chimpanzees: Captive versus wild environments

Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene

Mid-Pliocene hominin diversity revisited

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