U–Pb-dated flowstones restrict South African early hominin record to dry climate phases

Objectives: In humans it has been shown that abrasive particles in the diet result in increased tooth wear and less intense chewing behavior, both of which decrease chewing efficiency. This behavioral response may also exist in non-human primates as a means to reduce the wear effect of dust-laden food. Here we tested whether the periodical occurrence of abrasive dust particles in the diet of Western chimpanzees affects tooth wear and reduces chewing efficiency.Materials and methods: We measured fecal particle size of undigested food matter as an indicator of chewing efficiency in 13 Western chimpanzees of the Taï National Park (Ivory Coast) before (wet), after (wet) and during a dust-rich (dry) period. Moreover, feeding data were compiled for a further 12 chimpanzees and matched to three-dimensional surface texture data measured on two molar facets of 26 skulls of the same population.Results: Fecal particles were larger during the dry period, indicating a reduced chewing efficiency compared to wet periods; age and sex did not have an effect. Concomitantly, dust led to an increase of abrasive wear evidenced by smaller texture features and higher density of fine furrows on wear facets.Discussion: Our findings show that a periodical increase in dust loads on foods places a dietaryphysiological stress on the digestive system in chimpanzees. We suggest that the impact of extrinsic abrasive particles from globally acting periodical dust-laden winds may affect evolutionary fitness. Further studies are required to elucidate this relationship in other non-human primates and fossil hominins. K E Y W O R D S abrasive particles, fecal particle size, mastication, Taï, texture

Section: Discussionmentioning

confidence: 99%

Dust affects chewing efficiency and tooth wear in forest dwelling Western chimpanzees (Pan troglodytesverus)

Schulz‐Kornas

Stuhlträger

Clauss³

et al. 2019

“…The tooth, DNH 40, is a left maxillary third molar (Moggi‐Cecchi et al, ) dated to 2.0–1.5 Ma (Keyser, Menter, Moggi‐Cecchi, Pickering, & Berger, ; Pickering et al, ). A full morphological description is provided in Moggi‐Cecchi et al ().…”

Section: Methodsmentioning

confidence: 99%

Root caries on a Paranthropus robustus third molar from Drimolen

Towle

Riga

Irish

et al. 2019

Objectives: Dental caries is often perceived as a modern human disease. However, their presence is documented in many early human groups, various nonhuman primates and, increasingly, our hominin ancestors and relatives. In this study, we describe an antemortem lesion on the root of a Paranthropus robustus third molar from Drimolen, South Africa, which likely represents another example of caries in fossil hominins.Materials and Methods: The molar, DNH 40, is dated to 2.0-1.5 Ma and displays a lesion on the mesial root surface, extending from the cementoenamel junction 3 mm down toward the apex. The position and severity of the lesion was macroscopically recorded and micro-CT scanned to determine the extent of dentine involvement.Results: A differential diagnosis indicates root caries, as the lesion is indistinguishable from clinical examples. Although necrotic in appearance, external tertiary dentine is evident on a micro CT scan. Gingival recession and/or continuous eruption of the tooth as a result of extensive occlusal wear would have occurred to facilitate caries formation. Therefore, the lesion is likely linked to relative old age of this individual.Discussion: This new example increases the total number of carious lesions described in P. robustus teeth to 10, on occlusal, interproximal, and now, root surfaces. Beyond the consumption of caries-causing food, caries formation would have also required the presence of requisite intraoral cariogenic bacteria in this individual and the species. Of interest, the presence of tertiary dentine on the outward surface suggests the DNH 40 lesion may have been arrested, that is, no longer active, perhaps relating to a change in diet or oral microbiome just prior to the individual's death. K E Y W O R D Scaries, dental pathology, hominins, South Africa

“…Accordingly, one might consider the possibility of a temporally mixed sample, with specimens representing a significant amount of evolutionary time. Under this hypothesis, SKW 18 may represent a geologically younger/older and phylogenetically more derived/primitive Paranthropus population as compared to SK 46 and SK 47 that could be found at the same time at Drimolen (Pickering et al, ). However, without a clear stratigraphic control, it is nearly impossible to evaluate potential time differences between the specimens.…”

Section: Discussionmentioning

confidence: 99%

“…1.5 million years based on correlations with Member 1 of Swartkrans (Gibbon et al, ; Keyser, ; Keyser et al, ). More recently, U–Pb dating methods applied on top, middle, and basal flowstones at Drimolen revealed an age of 2.67–1.79 Ma (Pickering et al, ). All Australopithecus , Paranthropus and early Homo specimens are housed in the Ditsong National Museum of Natural History in Pretoria and the Evolutionary Studies Institute at the University of the Witwatersrand in Johannesburg (South Africa; Table ).…”

Section: Methodsmentioning

confidence: 99%

The inner ear of the Paranthropus specimen DNH 22 from Drimolen, South Africa

Beaudet

2019

Objectives: Morphological variation within the southern African hypodigm of Paranthropus has been the focus of major interest since the earliest discoveries in the "Cradle of Humankind." Given the relevance of the bony labyrinth for investigating fossil primate paleobiodiversity, this article aims to provide additional evidence for assessing the degree of regional variation within Paranthropus through the comparative analysis of the inner ear of DNH 22.Materials and methods: As comparative material, 18 southern African hominin specimens from Sterkfontein, Swartkrans, and Makapansgat (plus published data from Kromdraai B), attributed to Australopithecus, early Homo or Paranthropus, as well as 10 extant human and 10 extant common chimpanzee specimens are investigated. A landmark-based geometric morphometric method is applied for quantitatively assessing labyrinthine morphology. Additionally, cochlear parameters and oval window area are measured.Results: In terms of semicircular canal and cochlear shape, DNH 22 most resembles the Paranthropus specimen SKW 18 from Swartkrans. Both specimens differ from the other Paranthropus specimens investigated in this study by an anteroposteriorly large posterior semicircular canal and a cochlea with loose turns in the apical portion.Conversely, the oval window area in DNH 22 closely fits the range observed in Paranthropus from Swartkrans and Kromdraai B.Discussion: The inner ear of the DNH 22 specimen represents a unique opportunity to provide further insight into the early hominin labyrinthine variation pattern. In particular, the description of DNH 22 raises critical questions on the diversity of the vestibular system and evolutionary pattern of the auditory apparatus in Paranthropus. K E Y W O R D Scochlea, Cradle of Humankind, early hominins, Plio-Pleistocene, semicircular canals