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Chai H. Edge chipping patterns in posterior teeth of hominins and apes. J Mech Behav Biomed Mater 2024; 156:106582. [PMID: 38781774 DOI: 10.1016/j.jmbbm.2024.106582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 05/11/2024] [Accepted: 05/14/2024] [Indexed: 05/25/2024]
Abstract
Chip scars in fossil teeth are a lasting evidence that bears on human evolution. Chip dimensions in posterior teeth of hominins, apes and white-lipped peccary (Tayassu pecari) are measured from published occlusal images. The results are plotted as D/Dm vs. h/Dm, where h, D and Dm denote indent distance, chip width and mean tooth crown diameter. The hominin species follow a similar pattern where D/Dm monotonically increases up to h/Dm ≈ 0.3. The behavior for the apes is characterized by two phases. In the first, h/Dm monotonically increases up to h/Dm ≈ 0.26 while in the second (h/Dm ≈ 0.26 to 0.42), D/Dm experiences a drastic change in behavior. The interpretation of chip morphology is assisted by results from controlled spherical indentation tests on extracted human molars. This study shows that in addition to the commonly recognized chipping due to cusp loading, a chip may also initiate from the inner wall of the tooth's central fossa. Accordingly, it is suggested that the chipping in hominins generally initiates from a (worn) cusp while that in apes involves cusp loading up to h/Dm ≈ 0.26 and fossa loading thereafter. The behavior for T. pecari is much similar to that of the apes. The fossa chipping is facilitated by a consumption of hard, large-size diet (e.g., plants, roots, barks and nuts) and presence of broad central fossa, conditions that are met in apes. Finally, a simple expression for the critical chipping force Pch due to fossa loading is developed.
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Affiliation(s)
- Herzl Chai
- School of Mechanical Engineering, Tel-Aviv University, Tel-Aviv, Israel.
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Fannin LD, Swedell L, McGraw WS. Enamel chipping and its ecological correlates in African papionins: Implications for hominin feeding behavior. J Hum Evol 2023; 177:103330. [PMID: 36898301 DOI: 10.1016/j.jhevol.2023.103330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 01/23/2023] [Accepted: 01/25/2023] [Indexed: 03/12/2023]
Abstract
African papionins are classic paleoecological referents for fossil hominins. Enamel chips on the teeth of baboons and hominins are argued to represent responses to similar dietary habits; however, a comprehensive analysis of modern papionin chipping is lacking, leaving open the question of analog suitability. Here, we investigate patterns of antemortem enamel chipping across a diverse set of African papionin species occupying a range of ecological niches. We compare papionin chipping frequencies to estimates for Plio-Pleistocene hominins to address hypotheses of habitat and/or dietary similarities. Antemortem chips in seven African papionin species were scored on intact postcanine teeth (P3-M3) using established protocols. Chip size was scored on a tripartite scale. Papio hamadryas and Papio ursinus-two common paleoecological referents-display higher levels of chipping than Plio-Pleistocene hominin taxa (Australopithecus and Paranthropus) posited to have similar dietary habits. Papio populations occupying dry or highly seasonal habitats accumulate more large chips than Papio taxa occupying more mesic habitats, and terrestrial papionins chip their teeth more often than closely related taxa occupying arboreal niches. Chipping is present on the teeth of all Plio-Pleistocene hominins; however, chipping in baboons (P. ursinus and P. hamadryas) consistently exceeds most hominin taxa. Chipping frequencies on their own do not reliably sort taxa into major dietary groupings. We conclude that the large differences in chipping frequency may instead reflect habitat use and food processing idiosyncrasies. Less chipping in Plio-Pleistocene hominin teeth compared to modern Papio is more likely attributable to differences in dental morphology rather than diet.
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Affiliation(s)
- Luke D Fannin
- Department of Anthropology, Dartmouth College, Hanover, NH, 03755, USA; Graduate Program in Ecology, Evolution, Environment, and Society, Dartmouth College, Hanover, NH, 03755, USA.
| | - Larissa Swedell
- Department of Anthropology, Queens College, City University of New York, Flushing, NY, 11367, USA; Anthropology Program, Graduate Center, City University of New York, New York, NY, 10016, USA; New York Consortium in Evolutionary Primatology, New York, NY, 10016, USA; Department of Archaeology, University of Cape Town, Rondebosch, Western Cape, 7700, South Africa
| | - W Scott McGraw
- Department of Anthropology, The Ohio State University, Columbus, OH, 43210, USA
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Estimates of absolute crown strength and bite force in the lower postcanine dentition of Gigantopithecus blacki. J Hum Evol 2023; 175:103313. [PMID: 36709569 DOI: 10.1016/j.jhevol.2022.103313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 12/18/2022] [Accepted: 12/18/2022] [Indexed: 01/30/2023]
Abstract
Gigantopithecus blacki is hypothesized to have been capable of processing mechanically challenging foods, which likely required this species to have high dental resistance to fracture and/or large bite force. To test this hypothesis, we used two recently developed approaches to estimate absolute crown strength and bite force of the lower postcanine dentition. Sixteen Gigantopithecus mandibular permanent cheek teeth were scanned by micro-computed tomography. From virtual mesial cross-sections, we measured average enamel thickness and bi-cervical diameter to estimate absolute crown strength, and cuspal enamel thickness and dentine horn angle to estimate bite force. We compared G. blacki with a sample of extant great apes (Pan, Pongo, and Gorilla) and australopiths (Australopithecus anamensis, Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus, and Paranthropus boisei). We also evaluated statistical differences in absolute crown strength and bite force between the premolars and molars for G. blacki. Results reveal that molar crown strength is absolutely greater, and molar bite force absolutely higher, in G. blacki than all other taxa except P. boisei, suggesting that G. blacki molars have exceptionally high resistance to fracture and the ability to generate exceptionally high bite force. In addition, G. blacki premolars have comparable absolute crown strength and larger bite force capabilities compared with its molars, implying possible functional specializations in premolars. The dental specialization of G. blacki could thus represent an adaptation to further facilitate the processing of mechanically challenging foods. While it is currently not possible to determine which types of foods were actually consumed by G. blacki through this study, direct evidence (e.g. dental chipping and microwear) left by the foods eaten by G. blacki could potentially lead to greater insights into its dietary ecology.
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Ledogar JA, Senck S, Villmoare BA, Smith AL, Weber GW, Richmond BG, Dechow PC, Ross CF, Grosse IR, Wright BW, Wang Q, Byron C, Benazzi S, Carlson KJ, Carlson KB, Pryor McIntosh LC, van Casteren A, Strait DS. Mechanical compensation in the evolution of the early hominin feeding apparatus. Proc Biol Sci 2022; 289:20220711. [PMID: 35703052 DOI: 10.1098/rspb.2022.0711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Australopiths, a group of hominins from the Plio-Pleistocene of Africa, are characterized by derived traits in their crania hypothesized to strengthen the facial skeleton against feeding loads and increase the efficiency of bite force production. The crania of robust australopiths are further thought to be stronger and more efficient than those of gracile australopiths. Results of prior mechanical analyses have been broadly consistent with this hypothesis, but here we show that the predictions of the hypothesis with respect to mechanical strength are not met: some gracile australopith crania are as strong as that of a robust australopith, and the strength of gracile australopith crania overlaps substantially with that of chimpanzee crania. We hypothesize that the evolution of cranial traits that increased the efficiency of bite force production in australopiths may have simultaneously weakened the face, leading to the compensatory evolution of additional traits that reinforced the facial skeleton. The evolution of facial form in early hominins can therefore be thought of as an interplay between the need to increase the efficiency of bite force production and the need to maintain the structural integrity of the face.
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Affiliation(s)
- Justin A Ledogar
- Department of Health Sciences, East Tennessee State University, Johnson City, TN 37614, USA
| | - Sascha Senck
- Research Group Computed Tomography, University of Applied Sciences Upper Austria, 4600 Wels, Austria
| | - Brian A Villmoare
- Department of Anthropology, University of Nevada, Las Vegas, NV 89154, USA
| | - Amanda L Smith
- Department of Anatomy, Pacific Northwest University of Health Sciences, Yakima, WA 98901, USA
| | - Gerhard W Weber
- Department of Evolutionary Anthropology, University of Vienna, 1030 Vienna, Austria.,Human Evolution and Archaeological Sciences (HEAS), University of Vienna, 1030 Vienna, Austria
| | | | - Paul C Dechow
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX 75246, USA
| | - Callum F Ross
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA
| | - Ian R Grosse
- Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA 01003, USA
| | - Barth W Wright
- Department of Surgery, University of Kansas Medical Center, Kansas City, KS 66106, USA
| | - Qian Wang
- Department of Biomedical Sciences, Texas A&M University College of Dentistry, Dallas, TX 75246, USA
| | - Craig Byron
- Department of Biology, Mercer University, Macon, GA 31207, USA
| | - Stefano Benazzi
- Department of Cultural Heritage, University of Bologna, Ravenna 48121, Italy
| | - Kristian J Carlson
- Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.,Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Keely B Carlson
- Department of Anthropology, Texas A&M University, College Station, TX 77843, USA
| | - Leslie C Pryor McIntosh
- Department of Bio-Medical Sciences, Philadelphia College of Osteopathic Medicine South Georgia, Moultrie, GA 31768, USA
| | - Adam van Casteren
- School of Biological Sciences, University of Manchester, Oxford Road, Manchester, UK
| | - David S Strait
- Department of Anthropology, Washington University in St. Louis, St. Louis, MO 63103, USA.,Palaeo-Research Institute, University of Johannesburg, Auckland Park, Johannesburg, Gauteng, South Africa
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