1
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Selig KR. Hypoconulid loss in cercopithecins: Functional and developmental considerations. J Hum Evol 2024; 187:103479. [PMID: 38181576 DOI: 10.1016/j.jhevol.2023.103479] [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: 05/29/2023] [Revised: 11/28/2023] [Accepted: 11/28/2023] [Indexed: 01/07/2024]
Abstract
Cercopithecins differ from papionins in lacking a M3 hypoconulid. Although this loss may be related to dietary differences, the functional and developmental ramifications of hypoconulid loss are currently unclear. The following makes use of dental topographic analysis to quantify shape variation in a sample of cercopithecin M3s, as well as in a sample of Macaca, which has a hypoconulid. To help understand the consequences of hypoconulid loss, Macaca M3s were virtually cropped to remove the hypoconulid and were also subjected to dental topographic analysis. The patterning cascade model and the inhibitory cascade model attempt to explain variation in cusp pattern and molar proportions, respectively. These models have both previously been used to explain patterns of variation in cercopithecines, but have not been examined in the context of hypoconulid loss. For example, previous work suggests that earlier developing cusps impact the development of later developing cusps (i.e., the hypoconulid) and that cercopithecines do not conform to the predictions of the inhibitory cascade model in that the size of the molars is not linear moving distally. Results of the current study suggest that the loss of the hypoconulid is associated with a reduction in dental topography among cercopithecins, which is potentially related to diet, although the connection to diet is not necessarily clear. Results also suggest that the loss of the hypoconulid can be explained by the patterning cascade model, and that hypoconulid loss explains the apparent lack of support for the inhibitory cascade model among cercopithecines. These findings highlight the importance of a holistic approach to studying variation in molar proportions and developmental models.
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Affiliation(s)
- Keegan R Selig
- Department of Evolutionary Anthropology, Duke University, Biological Sciences Building, 130 Science Drive, Durham, NC, 27708, USA.
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2
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Chapple SA, Skinner MM. A tooth crown morphology framework for interpreting the diversity of primate dentitions. Evol Anthropol 2023; 32:240-255. [PMID: 37486115 DOI: 10.1002/evan.21994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 03/25/2023] [Accepted: 06/19/2023] [Indexed: 07/25/2023]
Abstract
Variation in tooth crown morphology plays a crucial role in species diagnoses, phylogenetic inference, and the reconstruction of the evolutionary history of the primate clade. While a growing number of studies have identified developmental mechanisms linked to tooth size and cusp patterning in mammalian crown morphology, it is unclear (1) to what degree these are applicable across primates and (2) which additional developmental mechanisms should be recognized as playing important roles in odontogenesis. From detailed observations of lower molar enamel-dentine junction morphology from taxa representing the major primate clades, we outline multiple phylogenetic and developmental components responsible for crown patterning, and formulate a tooth crown morphology framework for the holistic interpretation of primate crown morphology. We suggest that adopting this framework is crucial for the characterization of tooth morphology in studies of dental development, discrete trait analysis, and systematics.
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Affiliation(s)
- Simon A Chapple
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
| | - Matthew M Skinner
- School of Anthropology and Conservation, University of Kent, Canterbury, UK
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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3
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Measuring Molarization: Change Through Time in Premolar Function in An Extinct Stem Primate Lineage. J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09623-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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4
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Hardin AM, Knigge RP, Duren DL, Williams-Blangero S, Subedi J, Mahaney MC, Sherwood RJ. Genetic influences on dentognathic morphology in the Jirel population of Nepal. Anat Rec (Hoboken) 2022; 305:2137-2157. [PMID: 34981668 PMCID: PMC9250551 DOI: 10.1002/ar.24857] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 12/12/2022]
Abstract
Patterns of genetic variation and covariation impact the evolution of the craniofacial complex and contribute to clinically significant malocclusions in modern human populations. Previous quantitative genetic studies have estimated the heritabilities and genetic correlations of skeletal and dental traits in humans and nonhuman primates, but none have estimated these quantitative genetic parameters across the dentognathic complex. A large and powerful pedigree from the Jirel population of Nepal was leveraged to estimate heritabilities and genetic correlations in 62 maxillary and mandibular arch dimensions, incisor and canine lengths, and post-canine tooth crown areas (N ≥ 739). Quantitative genetic parameter estimation was performed using maximum likelihood-based variance decomposition. Residual heritability estimates were significant for all traits, ranging from 0.269 to 0.898. Genetic correlations were positive for all trait pairs. Principal components analyses of the phenotypic and genetic correlation matrices indicate an overall size effect across all measurements on the first principal component. Additional principal components demonstrate positive relationships between post-canine tooth crown areas and arch lengths and negative relationships between post-canine tooth crown areas and arch widths, and between arch lengths and arch widths. Based on these findings, morphological variation in the human dentognathic complex may be constrained by genetic relationships between dental dimensions and arch lengths, with weaker genetic correlations between these traits and arch widths allowing for variation in arch shape. The patterns identified are expected to have impacted the evolution of the dentognathic complex and its genetic architecture as well as the prevalence of dental crowding in modern human populations.
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Affiliation(s)
- Anna M. Hardin
- Biology Department, Western Oregon University
- Craniofacial Research Center, Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine
- Department of Orthopaedic Surgery, University of Missouri School of Medicine
| | - Ryan P. Knigge
- Craniofacial Research Center, Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine
- Department of Orthopaedic Surgery, University of Missouri School of Medicine
- Department of Integrative Biology and Physiology, University of Minnesota Medical School
| | - Dana L. Duren
- Craniofacial Research Center, Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine
- Department of Orthopaedic Surgery, University of Missouri School of Medicine
| | - Sarah Williams-Blangero
- South Texas Diabetes and Obesity Institute, School of Medicine, University of Texas Rio Grande Valley
| | | | - Michael C. Mahaney
- South Texas Diabetes and Obesity Institute, School of Medicine, University of Texas Rio Grande Valley
- Department of Human Genetics, School of Medicine, University of Texas Rio Grande Valley
| | - Richard J. Sherwood
- Craniofacial Research Center, Department of Pathology and Anatomical Sciences, University of Missouri School of Medicine
- Department of Orthopaedic Surgery, University of Missouri School of Medicine
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5
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Bermúdez de Castro JM, Modesto‐Mata M, García‐Campos C, Sarmiento S, Martín‐Francés L, Martínez de Pinillos M, Martinón‐Torres M. Testing the inhibitory cascade model in a recent human sample. J Anat 2021; 239:1170-1181. [PMID: 34227109 PMCID: PMC8546523 DOI: 10.1111/joa.13500] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 06/09/2021] [Accepted: 06/10/2021] [Indexed: 01/09/2023] Open
Abstract
The Inhibitory Cascade Model was proposed by Kavanagh and colleagues (Nature, 449, 427-433 [2007]) after their experimental studies on the dental development of murine rodent species. These authors described an activator-inhibitor mechanism that has been employed to predict evolutionary size patterns of mammalian teeth, including hominins. In the present study, we measured the crown area of the three lower permanent molars (M1, M2, and M3) of a large recent modern human sample of male and female individuals from a collection preserved at the Institute of Anthropology of the University of Coimbra (Portugal). The main aim of the present study is to test if the size molar patterns observed in this human sample fits the Inhibitory Cascade Model. For this purpose, we first measured the crown area in those individuals preserving the complete molar series. Measurements were taken in photographs, using a planimeter and following well-tested techniques used in previous works. We then plot the M3 /M1 and M2 /M1 size ratios. Our results show that the premise of the Inhibitory Cascade Model, according to which the average of the crown area of M2 is approximately one-third of the sum of the crown area of the three molars, is fulfilled. However, our results also show that the individual values of a significant number of males and females are out of the 95% confidence interval predicted by the Inhibitory Cascade Model in rodents. As a result, the present analyses suggest that neither the sample of males, nor that of females, nor the pooled sample fits the Inhibitory Cascade Model. It is important to notice that, although this model has been successfully tested in a large number of current human populations, to the best of our knowledge this is the first study in which individual data have been obtained in a recent human population rather than using the average of the sample. Our results evince that, at the individual level, some factors not yet known could interfere with this model masking the modulation of the size on the molar series in modern humans. We suggest that the considerable delay in the onset of M3 formation in modern humans could be related to a weakening of the possible activation/inhibition process for this tooth. Finally, and in support of our conclusions, we have checked that the absolute and relative size of M1 and M2 is not related to the M3 agenesis in our sample. In line with other studies in primates, our results do not support the Inhibitory Cascade Model in a recent human sample. Further research is needed to better understand the genetic basis of this mechanism and its relationship to the phenotype. In this way, we may be able to find out which evolutionary changes may be responsible for the deviations observed in many species, including Homo sapiens.
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Affiliation(s)
- José María Bermúdez de Castro
- CENIEH (National Research Center on Human Evolution)BurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
| | - Mario Modesto‐Mata
- Equipo Primeros Pobladores de ExtremaduraCasa de la Cultura Rodríguez MoñinoCáceresSpain
| | - Cecilia García‐Campos
- CENIEH (National Research Center on Human Evolution)BurgosSpain
- Fundación AtapuercaIbeas de JuarrosBurgosSpain
| | | | - Laura Martín‐Francés
- CENIEH (National Research Center on Human Evolution)BurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
- Fundación AtapuercaIbeas de JuarrosBurgosSpain
| | | | - María Martinón‐Torres
- CENIEH (National Research Center on Human Evolution)BurgosSpain
- Anthropology DepartmentUniversity College LondonLondonUK
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6
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Irish JD, Grabowski M. Relative tooth size, Bayesian inference, and Homo naledi. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 176:262-282. [PMID: 34190335 DOI: 10.1002/ajpa.24353] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Revised: 05/04/2021] [Accepted: 06/08/2021] [Indexed: 01/29/2023]
Abstract
OBJECTIVES Size-corrected tooth crown measurements were used to estimate phenetic affinities among Homo naledi (~335-236 ka) and 11 other Plio-Pleistocene and recent species. To assess further their efficacy, and identify dental evolutionary trends, the data were then quantitatively coded for phylogenetic analyses. Results from both methods contribute additional characterization of H. naledi relative to other hominins. MATERIALS AND METHODS After division by their geometric mean, scaled mesiodistal and buccolingual dimensions were used in tooth size apportionment analysis to compare H. naledi with Australopithecus africanus, A. afarensis, Paranthropus robustus, P. boisei, H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, H. sapiens, and Pan troglodytes. These data produce equivalently scaled samples unaffected by interspecific size differences. The data were then gap-weighted for Bayesian inference. RESULTS Congruence in interspecific relationships is evident between methods, and with many inferred from earlier systematic studies. However, the present results place H. naledi as a sister taxon to H. habilis, based on a symplesiomorphic pattern of relative tooth size. In the preferred Bayesian phylogram, H. naledi is nested within a clade comprising all Homo species, but it shares some characteristics with australopiths and, particularly, early Homo. DISCUSSION Phylogenetic analyses of relative tooth size yield information about evolutionary dental trends not previously reported in H. naledi and the other hominins. Moreover, with an appropriate model these data recovered plausible evolutionary relationships. Together, the findings support recent study suggesting H. naledi originated long before the geological date of the Dinaledi Chamber, from which the specimens under study were recovered.
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Affiliation(s)
- Joel D Irish
- Research Centre in Evolutionary Anthropology and Palaeoecology, School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK.,The Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Johannesburg, South Africa
| | - Mark Grabowski
- Research Centre in Evolutionary Anthropology and Palaeoecology, School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK.,Centre for Ecology and Evolutionary Synthesis, Department of Biosciences, University of Oslo, Oslo, Norway
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7
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Abstract
Identifying developmental explanations for the evolution of complex structures like mammalian molars is fundamental to studying phenotypic variation. Previous study showed that a "morphogenetic gradient" of molar proportions was explained by a balance between inhibiting/activating activity from earlier developing molars, termed the inhibitory cascade model (ICM). Although this model provides an explanation for variation in molar proportions, what remains poorly understood is if molar shape, or specifically complexity (i.e., the number of cusps, crests), can be explained by the same developmental model. Here, we show that molar complexity conforms to the ICM, following a linear, morphogenetic gradient along the molar row. Moreover, differing levels of inhibiting/activating activity produce contrasting patterns of molar complexity depending on diet. This study corroborates a model for the evolution of molar complexity that is developmentally simple, where only small-scale developmental changes need to occur to produce change across the entire molar row, with this process being mediated by an animal's ecology. The ICM therefore provides a developmental framework for explaining variation in molar complexity and a means for testing developmental hypotheses in the broader context of mammalian evolution.
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8
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Bermúdez de Castro JM, Modesto‐Mata M, Martín‐Francés L, García‐Campos C, Martínez de Pinillos M, Martinón‐Torres M. Testing the inhibitory cascade model in the Middle Pleistocene Sima de los Huesos (Sierra de Atapuerca, Spain) hominin sample. J Anat 2021; 238:173-184. [PMID: 32839991 PMCID: PMC7755082 DOI: 10.1111/joa.13292] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/04/2020] [Accepted: 07/13/2020] [Indexed: 01/03/2023] Open
Abstract
The Middle Pleistocene Sima de los Huesos (SH) site has yielded more than 7.500 human fossil remains belonging to a minimum of 29 individuals. Most of these individuals preserve either the complete mandibular molar series or at least the first (M1 ) and second (M2 ) molars. The inhibitory cascade mathematical model was proposed by Kavanagh et al. (Nature, 449, 427-433 [2007]) after their experimental studies on the dental development of murine rodent species. The activator-inhibitor mechanism of this model has shown its ability for predicting evolutionary size patterns of mammalian teeth, including hominins. The main aim of this study is to test whether the size molar patterns observed in the SH hominins fit the inhibitory cascade model. With this purpose, we have measured the crown area of all SH molars in photographs, using a planimeter and following techniques used and well contrasted in previous works. Following one of the premises of the inhibitory cascade model, we expect that the central tooth (M2 in our case) of a triplet would have the average size of the two outer teeth. The absolute difference between the observed and the expected values for the M2 s ranges from 0.23 to 8.46 mm2 in the SH sample. In terms of percentage, the difference ranges between 0.25% and 10.34%, although in most cases, it is below 5%. The plot of the estimated M3 /M1 and M2 /M1 size ratios obtained in the SH hominins occupies a small area of the theoretical developmental morphospace obtained for rodent species. In addition, the majority of the values are placed near the theoretical line which defines the relationship predicted by the inhibitory cascade model in these mammals. The values of the slope and intercept of the reduced major regression obtained for the SH individuals do not differ significantly from those obtained for rodent species, thus confirming that the size of the molars of the SH hominins fits the inhibitory cascade model. We discuss these results in terms of dental development. Despite the promising results in the SH sample, we draw the attention to the fact that most Early Pleistocene Homo specimens exhibit a pattern (M1 < M2 > M3 ), which is outside the expected theoretical morphospace predicted by the inhibitory cascade model. The shift from the M1 < M2 < M3 size relationship observed in early hominins (including H. habilis) to the M1 > M2 > M3 size relationship, which is predominant in modern humans, includes sequences that depart from predictions of the inhibitory cascade model. Additional studies are required to understand these deviations.
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Affiliation(s)
- José María Bermúdez de Castro
- CENIEH (National Research Center on Human EvolutionBurgosSpain,Anthropology DepartmentUniversity College LondonLondonUK
| | - Mario Modesto‐Mata
- Equipo Primeros Pobladores de ExtremaduraCasa de la Cultura Rodríguez MoñinoCáceresSpain,Fundación AtapuercaBurgosSpain
| | - Laura Martín‐Francés
- CENIEH (National Research Center on Human EvolutionBurgosSpain,Anthropology DepartmentUniversity College LondonLondonUK,Fundación AtapuercaBurgosSpain
| | - Cecilia García‐Campos
- CENIEH (National Research Center on Human EvolutionBurgosSpain,Fundación AtapuercaBurgosSpain
| | | | - María Martinón‐Torres
- CENIEH (National Research Center on Human EvolutionBurgosSpain,Anthropology DepartmentUniversity College LondonLondonUK
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9
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Hardin AM. Genetic correlations in the rhesus macaque dentition. J Hum Evol 2020; 148:102873. [PMID: 33059308 DOI: 10.1016/j.jhevol.2020.102873] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Revised: 08/07/2020] [Accepted: 08/07/2020] [Indexed: 12/31/2022]
Abstract
Quantitative genetic analyses can indicate how complex traits respond to natural selection by demonstrating the genetic relationships between features that constrain their evolution. Genetic correlations between dental measurements have been estimated previously in baboons, humans, and tamarins and indicate variable patterns of modularity by tooth type across these taxa. Here, heritabilities of, and genetic correlations between, linear dental measurements were estimated from the Cayo Santiago rhesus macaques (Macaca mulatta). Relationships between the genetic correlation matrix and matrices designed to test hypotheses of modularity by tooth type, region, function, and development were assessed using a random skewers approach. Dental measurements were found to be moderately to highly heritable, with 24 of 28 heritability estimates differing significantly (p < 0.05) from zero. Almost all genetic correlations between dental dimensions were positive. The genetic correlation matrix was most similar to a regionally modular matrix, with distinct anterior and postcanine tooth modules. This pattern is consistent with previous quantitative genetic analyses of baboons and previous phenotypic analyses of cercopithecoid primates. The existence of a genetic module for the canines and honing premolar was not supported. Ongoing selection pressures, rather than strong genetic constraints, are likely necessary to preserve functional relationships between the canines and honing premolar based on these findings. The genetic correlation matrix of the Cayo Santiago rhesus macaques mirrors patterns of phenotypic correlations observed for cercopithecoid primates broadly and demonstrates that genetic contributions to these patterns may be fairly stable over the course of cercopithecoid evolution. The quantitative genetic study of additional taxa will be necessary to determine whether the regional modularity of baboons and macaques, or the integrated pattern of humans and tamarins, is shared more broadly across primates.
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Affiliation(s)
- Anna M Hardin
- Department of Anthropology, University of Minnesota, Minneapolis, MN, 55455, USA; Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, 65212, USA.
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10
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A genotype:phenotype approach to testing taxonomic hypotheses in hominids. Naturwissenschaften 2020; 107:40. [PMID: 32870408 DOI: 10.1007/s00114-020-01696-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 04/20/2020] [Accepted: 08/19/2020] [Indexed: 10/23/2022]
Abstract
Paleontology has long relied on assumptions about the genetic and developmental influences on skeletal variation. The last few decades of developmental genetics have elucidated the genetic pathways involved in making teeth and patterning the dentition. Quantitative genetic analyses have refined this genotype:phenotype map even more, especially for primates. We now have the ability to define dental traits with a fair degree of fidelity to the underlying genetic architecture; for example, the molar module component (MMC) and the premolar-molar module (PMM) that have been defined through quantitative genetic analyses. We leverage an extensive dataset of extant and extinct hominoid dental variation to explore how these two genetically patterned phenotypes have evolved through time. We assess MMC and PMM to test the hypothesis that these two traits reveal a more biologically informed taxonomy at the genus and species levels than do more traditional measurements. Our results indicate that MMC values for hominids fall into two categories and that Homo is derived compared with earlier taxa. We find a more variable, species-level pattern for PMM. These results, in combination with previous research, demonstrate that MMC reflects the phenotypic output of a more evolutionarily stable, or phylogenetically congruent, genetic mechanism, and PMM is a reflection of a more evolutionarily labile mechanism. These results suggest that the human lineage since the split with chimpanzees may not represent as much genus-level variation as has been inferred from traits whose etiologies are not understood.
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11
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Vitek NS, Roseman CC, Bloch JI. Mammal Molar Size Ratios and the Inhibitory Cascade at the Intraspecific Scale. Integr Org Biol 2020; 2:obaa020. [PMID: 33791561 PMCID: PMC7750983 DOI: 10.1093/iob/obaa020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Mammalian molar crowns form a module in which measurements of size for individual teeth within a tooth row covary with one another. Molar crown size covariation is proposed to fit the inhibitory cascade model (ICM) or its variant the molar module component (MMC) model, but the inability of the former model to fit across biological scales is a concern in the few cases where it has been tested in Primates. The ICM has thus far failed to explain patterns of intraspecific variation, an intermediate biological scale, even though it explains patterns at both smaller organ-level and larger between-species biological scales. Studies of this topic in a much broader range of taxa are needed, but the properties of a sample appropriate for testing the ICM at the intraspecific level are unclear. Here, we assess intraspecific variation in relative molar sizes of the cotton mouse, Peromyscus gossypinus, to further test the ICM and to develop recommendations for appropriate sampling protocols in future intraspecific studies of molar size variation across Mammalia. To develop these recommendations, we model the sensitivity of estimates of molar ratios to sample size and simulate the use of composite molar rows when complete ones are unavailable. Similar to past studies on primates, our results show that intraspecific variance structure of molar ratios within the rodent P. gossypinus does not meet predictions of the ICM or MMC. When we extend these analyses to include the MMC, one model does not fit observed patterns of variation better than the other. Standing variation in molar size ratios is relatively constant across mammalian samples containing all three molars. In future studies, analyzing average ratio values will require relatively small minimum sample sizes of two or more complete molar rows. Even composite-based estimates from four or more specimens per tooth position can accurately estimate mean molar ratios. Analyzing variance structure will require relatively large sample sizes of at least 40-50 complete specimens, and composite molar rows cannot accurately reconstruct variance structure of ratios in a sample. Based on these results, we propose guidelines for intraspecific studies of molar size covariation. In particular, we note that the suitability of composite specimens for averaging mean molar ratios is promising for the inclusion of isolated molars and incomplete molar rows from the fossil record in future studies of the evolution of molar modules, as long as variance structure is not a key component of such studies.
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Affiliation(s)
- N S Vitek
- Department of Ecology & Evolution, Stony Brook University, 632 Life Sciences Building, Stony Brook, NY 11794-5245, USA.,Florida Museum of Natural History and Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - C C Roseman
- Department of Evolution, Ecology, and Behavior, University of Illinois, Champaign, IL 61820, USA
| | - J I Bloch
- Florida Museum of Natural History and Department of Biology, University of Florida, Gainesville, FL 32611, USA
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12
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Sadier A, Jackman WR, Laudet V, Gibert Y. The Vertebrate Tooth Row: Is It Initiated by a Single Organizing Tooth? Bioessays 2020; 42:e1900229. [PMID: 32347985 DOI: 10.1002/bies.201900229] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/20/2020] [Indexed: 01/10/2023]
Abstract
Teeth are one of the most fascinating innovations of vertebrates. Their diversity of shape, size, location, and number in vertebrates is astonishing. If the molecular mechanisms underlying the morphogenesis of individual teeth are now relatively well understood, thanks to the detailed experimental work that has been performed in model organisms (mainly mouse and zebrafish), the mechanisms that control the organization of the dentition are still a mystery. Mammals display simplified dentitions when compared to other vertebrates with only a single tooth row positioned in the anterior part of the mouth, whereas other vertebrates exhibit tooth rows in many locations. As proposed 60 years ago, tooth rows can be formed sequentially from an initiator tooth. Recent results in zebrafish have now largely confirmed this hypothesis. Here this observation is generalized upon and it is suggested that in most vertebrates tooth rows could form sequentially from a single initiator tooth.
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Affiliation(s)
- Alexa Sadier
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, 90095, USA
| | | | - Vincent Laudet
- Observatoire Océanologique de Banyuls-sur-Mer, UMR CNRS 7232 BIOM, Sorbonne Université Paris, 1, avenue Pierre Fabre, Banyuls-sur-Mer, 66650, France
| | - Yann Gibert
- University of Mississippi Medical Center, Department of Cell and Molecular Biology, 2500 North State Street, Jackson, MS, 39216, USA
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13
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Morita W, Morimoto N, Kono RT, Suwa G. Metameric variation of upper molars in hominoids and its implications for the diversification of molar morphogenesis. J Hum Evol 2019; 138:102706. [PMID: 31785453 DOI: 10.1016/j.jhevol.2019.102706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 10/20/2019] [Accepted: 10/20/2019] [Indexed: 11/18/2022]
Abstract
Metameric variation of molar size is in part associated with the dietary adaptations of mammals and results from slight alterations of developmental processes. Humans and great apes exhibit conspicuous variation in tooth morphology both between taxa and across tooth types. However, the manner in which metameric variation in molars emerged among apes and humans via evolutionary alterations in developmental processes remains largely unknown. In this study, we compare the enamel-dentine junction of the upper molars of humans-which closely correlates with morphology of the outer enamel surface and is less affected by wear-with that of the other extant hominoids: chimpanzees, bonobos, gorillas, orangutans, and gibbons. We used the morphometric mapping method to quantify and visualize three-dimensional morphological variation, and applied multivariate statistical analyses. Results revealed the following: 1) extant hominoids other than humans share a common pattern of metameric variation characterized by a largely linear change in morphospace; this indicates a relatively simple graded change in metameric molar shape; 2) intertaxon morphological differences become less distinct from the mesial to distal molars; and 3) humans diverge from the extant ape pattern in exhibiting a distinct metameric shape change trajectory in the morphospace. The graded shape change and lower intertaxon resolution from the mesial to distal molars are consistent with the concept of a 'key' tooth. The common metameric pattern observed among the extant nonhuman hominoids indicates that developmental patterns underlying metameric variation were largely conserved during ape evolution. Furthermore, the human-specific metameric pattern suggests considerable developmental modifications in the human lineage.
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Affiliation(s)
- Wataru Morita
- Developmental Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland; Department of Oral Functional Anatomy, Faculty of Dental Medicine, Hokkaido University, Hokkaido, Japan.
| | - Naoki Morimoto
- Laboratory of Physical Anthropology, Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan.
| | - Reiko T Kono
- Faculty of Letters, Keio University, Kanagawa, Japan
| | - Gen Suwa
- The University Museum, The University of Tokyo, Tokyo, Japan
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Monson TA, Boisserie J, Brasil MF, Clay SM, Dvoretzky R, Ravindramurthy S, Schmitt CA, Souron A, Takenaka R, Ungar PS, Yoo S, Zhou M, Zuercher ME, Hlusko LJ. Evidence of strong stabilizing effects on the evolution of boreoeutherian (Mammalia) dental proportions. Ecol Evol 2019; 9:7597-7612. [PMID: 31346425 PMCID: PMC6635932 DOI: 10.1002/ece3.5309] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 04/25/2019] [Accepted: 04/28/2019] [Indexed: 11/28/2022] Open
Abstract
The dentition is an extremely important organ in mammals with variation in timing and sequence of eruption, crown morphology, and tooth size enabling a range of behavioral, dietary, and functional adaptations across the class. Within this suite of variable mammalian dental phenotypes, relative sizes of teeth reflect variation in the underlying genetic and developmental mechanisms. Two ratios of postcanine tooth lengths capture the relative size of premolars to molars (premolar-molar module, PMM), and among the three molars (molar module component, MMC), and are known to be heritable, independent of body size, and to vary significantly across primates. Here, we explore how these dental traits vary across mammals more broadly, focusing on terrestrial taxa in the clade of Boreoeutheria (Euarchontoglires and Laurasiatheria). We measured the postcanine teeth of N = 1,523 boreoeutherian mammals spanning six orders, 14 families, 36 genera, and 49 species to test hypotheses about associations between dental proportions and phylogenetic relatedness, diet, and life history in mammals. Boreoeutherian postcanine dental proportions sampled in this study carry conserved phylogenetic signal and are not associated with variation in diet. The incorporation of paleontological data provides further evidence that dental proportions may be slower to change than is dietary specialization. These results have implications for our understanding of dental variation and dietary adaptation in mammals.
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Affiliation(s)
- Tesla A. Monson
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
- Human Evolution Research CenterUniversity of CaliforniaBerkeleyCalifornia
- Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeleyCalifornia
- Anthropologisches Institut und MuseumUniversität ZürichZürichSwitzerland
| | | | - Marianne F. Brasil
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
- Human Evolution Research CenterUniversity of CaliforniaBerkeleyCalifornia
| | - Selene M. Clay
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
- Department of Human GeneticsUniversity of ChicagoChicagoIllinois
| | - Rena Dvoretzky
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
| | | | | | | | - Risa Takenaka
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
- Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeleyCalifornia
| | - Peter S. Ungar
- Department of AnthropologyUniversity of ArkansasFayettevilleArkansas
| | - Sunwoo Yoo
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
| | - Michael Zhou
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
| | | | - Leslea J. Hlusko
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCalifornia
- Human Evolution Research CenterUniversity of CaliforniaBerkeleyCalifornia
- Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeleyCalifornia
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Heritability and genetic integration of tooth size in the South Carolina Gullah. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:505-521. [DOI: 10.1002/ajpa.23290] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/14/2017] [Accepted: 07/21/2017] [Indexed: 12/15/2022]
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Quantitative genetics provides predictive power for paleontological studies of morphological evolution. Proc Natl Acad Sci U S A 2016; 113:9142-4. [PMID: 27496325 DOI: 10.1073/pnas.1610454113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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The integration of quantitative genetics, paleontology, and neontology reveals genetic underpinnings of primate dental evolution. Proc Natl Acad Sci U S A 2016; 113:9262-7. [PMID: 27402751 DOI: 10.1073/pnas.1605901113] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Developmental genetics research on mice provides a relatively sound understanding of the genes necessary and sufficient to make mammalian teeth. However, mouse dentitions are highly derived compared with human dentitions, complicating the application of these insights to human biology. We used quantitative genetic analyses of data from living nonhuman primates and extensive osteological and paleontological collections to refine our assessment of dental phenotypes so that they better represent how the underlying genetic mechanisms actually influence anatomical variation. We identify ratios that better characterize the output of two dental genetic patterning mechanisms for primate dentitions. These two newly defined phenotypes are heritable with no measurable pleiotropic effects. When we consider how these two phenotypes vary across neontological and paleontological datasets, we find that the major Middle Miocene taxonomic shift in primate diversity is characterized by a shift in these two genetic outputs. Our results build on the mouse model by combining quantitative genetics and paleontology, and thereby elucidate how genetic mechanisms likely underlie major events in primate evolution.
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Asahara M, Saito K, Kishida T, Takahashi K, Bessho K. Unique pattern of dietary adaptation in the dentition of Carnivora: its advantage and developmental origin. Proc Biol Sci 2016. [PMCID: PMC4920314 DOI: 10.1098/rspb.2016.0375] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Carnivora is a successful taxon in terms of dietary diversity. We investigated the dietary adaptations of carnivoran dentition and the developmental background of their dental diversity, which may have contributed to the success of the lineage. A developmental model was tested and extended to explain the unique variability and exceptional phenotypes observed in carnivoran dentition. Carnivorous mammalian orders exhibited two distinct patterns of dietary adaptation in molars and only Carnivora evolved novel variability, exhibiting a high correlation between relative molar size and the shape of the first molar. Studies of Bmp7-hetero-deficient mice, which may exhibit lower Bmp7 expression, suggested that Bmp7 has pleiotropic effects on these two dental traits. Its effects are consistent with the pattern of dietary adaptation observed in Carnivora, but not that observed in other carnivorous mammals. A molecular evolutionary analysis revealed that Bmp7 sequence evolved by natural selection during ursid evolution, suggesting that it plays an evolutionary role in the variation of carnivoran dentition. Using mouse experiments and a molecular evolutionary analysis, we extrapolated the causal mechanism of the hitherto enigmatic ursid dentition (larger M2 than M1 and M3). Our results demonstrate how carnivorans acquired novel dental variability that benefits their dietary divergence.
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Affiliation(s)
- Masakazu Asahara
- Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Kazuyuki Saito
- Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kyoto Univerisity, Kyoto, Japan
| | | | - Katsu Takahashi
- Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kyoto Univerisity, Kyoto, Japan
| | - Kazuhisa Bessho
- Department of Oral and Maxillofacial Surgery, Graduate School of Medicine, Kyoto Univerisity, Kyoto, Japan
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Evans AR, Daly ES, Catlett KK, Paul KS, King SJ, Skinner MM, Nesse HP, Hublin JJ, Townsend GC, Schwartz GT, Jernvall J. A simple rule governs the evolution and development of hominin tooth size. Nature 2016; 530:477-80. [DOI: 10.1038/nature16972] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 01/07/2016] [Indexed: 11/09/2022]
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