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van Casteren A, Lucas PW, Strait DS, Michael S, Bierwisch N, Schwarzer N, Al-Fadhalah KJ, Almusallam AS, Thai LA, Saji S, Shekeban A, Swain MV. Evidence that metallic proxies are unsuitable for assessing the mechanics of microwear formation and a new theory of the meaning of microwear. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171699. [PMID: 29892367 PMCID: PMC5990759 DOI: 10.1098/rsos.171699] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 04/20/2018] [Indexed: 05/14/2023]
Abstract
Mammalian tooth wear research reveals contrasting patterns seemingly linked to diet: irregularly pitted enamel surfaces, possibly from consuming hard seeds, versus roughly aligned linearly grooved surfaces, associated with eating tough leaves. These patterns are important for assigning diet to fossils, including hominins. However, experiments establishing conditions necessary for such damage challenge this paradigm. Lucas et al. (Lucas et al. 2013 J. R. Soc. Interface10, 20120923. (doi:10.1098/rsif.2012.0923)) slid natural objects against enamel, concluding anything less hard than enamel would rub, not abrade, its surface (producing no immediate wear). This category includes all organic plant matter. Particles harder than enamel, with sufficiently angular surfaces, could abrade it immediately, prerequisites that silica/silicate particles alone possess. Xia et al. (Xia, Zheng, Huang, Tian, Chen, Zhou, Ungar, Qian. 2015 Proc. Natl Acad. Sci. USA112, 10 669-10 672. (doi:10.1073/pnas.1509491112)) countered with experiments using brass and aluminium balls. Their bulk hardness was lower than enamel, but the latter was abraded. We examined the ball exteriors to address this discrepancy. The aluminium was surfaced by a thin rough oxide layer harder than enamel. Brass surfaces were smoother, but work hardening during manufacture gave them comparable or higher hardness than enamel. We conclude that Xia et al.'s results are actually predicted by the mechanical model of Lucas et al. To explain wear patterns, we present a new model of textural formation, based on particle properties and presence/absence of silica(tes).
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Affiliation(s)
- Adam van Casteren
- Max Planck Weizmann Center for Integrative Archeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, Germany
| | - Peter W. Lucas
- Smithsonian Tropical Research Institute, Luis Clement Ave., Bldg. 401 Tupper Balboa Ancon, Panama, Republic of Panama
| | - David S. Strait
- Department of Anthropology, Washington University in St Louis, Campus Box 1114, One Brookings Drive, St Louis, MO 63130, USA
| | - Shaji Michael
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
| | - Nick Bierwisch
- Saxonian Institute of Surface Mechanics SIO, Tankow 2, 18569 Ummanz, Rügen, Germany
| | - Norbert Schwarzer
- Saxonian Institute of Surface Mechanics SIO, Tankow 2, 18569 Ummanz, Rügen, Germany
| | - Khaled J. Al-Fadhalah
- Department of Mechanical Engineering, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Abdulwahab S. Almusallam
- Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Lidia A. Thai
- Nanotechnology Research Facility, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Sreeja Saji
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
| | - Ali Shekeban
- Nanotechnology Research Facility, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Michael V. Swain
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
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van Casteren A, Lucas PW, Strait DS, Michael S, Bierwisch N, Schwarzer N, Al-Fadhalah KJ, Almusallam AS, Thai LA, Saji S, Shekeban A, Swain MV. Evidence that metallic proxies are unsuitable for assessing the mechanics of microwear formation and a new theory of the meaning of microwear. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171699. [PMID: 29892367 DOI: 10.5061/dryad.72431] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 04/20/2018] [Indexed: 05/27/2023]
Abstract
Mammalian tooth wear research reveals contrasting patterns seemingly linked to diet: irregularly pitted enamel surfaces, possibly from consuming hard seeds, versus roughly aligned linearly grooved surfaces, associated with eating tough leaves. These patterns are important for assigning diet to fossils, including hominins. However, experiments establishing conditions necessary for such damage challenge this paradigm. Lucas et al. (Lucas et al. 2013 J. R. Soc. Interface10, 20120923. (doi:10.1098/rsif.2012.0923)) slid natural objects against enamel, concluding anything less hard than enamel would rub, not abrade, its surface (producing no immediate wear). This category includes all organic plant matter. Particles harder than enamel, with sufficiently angular surfaces, could abrade it immediately, prerequisites that silica/silicate particles alone possess. Xia et al. (Xia, Zheng, Huang, Tian, Chen, Zhou, Ungar, Qian. 2015 Proc. Natl Acad. Sci. USA112, 10 669-10 672. (doi:10.1073/pnas.1509491112)) countered with experiments using brass and aluminium balls. Their bulk hardness was lower than enamel, but the latter was abraded. We examined the ball exteriors to address this discrepancy. The aluminium was surfaced by a thin rough oxide layer harder than enamel. Brass surfaces were smoother, but work hardening during manufacture gave them comparable or higher hardness than enamel. We conclude that Xia et al.'s results are actually predicted by the mechanical model of Lucas et al. To explain wear patterns, we present a new model of textural formation, based on particle properties and presence/absence of silica(tes).
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Affiliation(s)
- Adam van Casteren
- Max Planck Weizmann Center for Integrative Archeology and Anthropology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103, Leipzig, Germany
| | - Peter W Lucas
- Smithsonian Tropical Research Institute, Luis Clement Ave., Bldg. 401 Tupper Balboa Ancon, Panama, Republic of Panama
| | - David S Strait
- Department of Anthropology, Washington University in St Louis, Campus Box 1114, One Brookings Drive, St Louis, MO 63130, USA
| | - Shaji Michael
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
| | - Nick Bierwisch
- Saxonian Institute of Surface Mechanics SIO, Tankow 2, 18569 Ummanz, Rügen, Germany
| | - Norbert Schwarzer
- Saxonian Institute of Surface Mechanics SIO, Tankow 2, 18569 Ummanz, Rügen, Germany
| | - Khaled J Al-Fadhalah
- Department of Mechanical Engineering, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Abdulwahab S Almusallam
- Department of Chemical Engineering, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Lidia A Thai
- Nanotechnology Research Facility, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Sreeja Saji
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
| | - Ali Shekeban
- Nanotechnology Research Facility, College of Engineering and Petroleum, Kuwait University, PO Box 5969, Safat 13060, Kuwait
| | - Michael V Swain
- Department of Bioclinical Sciences, Faculty of Dentistry, Kuwait University, PO Box 24923, Safat 11310, Kuwait
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