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Farrera A. Formal models for the study of the relationship between fluctuating asymmetry and fitness in humans. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2022; 179:73-84. [PMID: 36790746 PMCID: PMC9540978 DOI: 10.1002/ajpa.24588] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 06/04/2022] [Accepted: 06/20/2022] [Indexed: 11/11/2022]
Abstract
OBJECTIVES To evaluate three of the main verbal models that have been proposed to explain the relationship between fluctuating asymmetry and fitness in humans: the "good genes," the "good development," and the "growth" hypotheses. MATERIALS AND METHODS A formal model was generated for each verbal model following three steps. First, based on the literature, a theoretical causal model and the theoretical object of inquiry were outlined. Second, an empirical causal model and the targets of inference were defined using observational data of facial asymmetries and life-history traits related to fitness. Third, generalized linear models and causal inference were used as the estimation strategy. RESULTS The results suggest that the theoretical and empirical assumptions of the "good genes" hypothesis should be reformulated. The results were compatible with most of the empirical assumptions of "the good development" hypothesis but suggest that further discussion of its theoretical assumptions is needed. The results were less informative about the "growth" hypothesis, both theoretically and empirically. There was a positive association between facial fluctuating asymmetry and the number of offspring that was not compatible with any of the empirical causal models evaluated. CONCLUSIONS Although the three hypotheses focus on different aspects of the link between asymmetry and fitness, their overlap opens the possibility of a unified theory on the subject. The results of this study make explicit which assumptions need to be updated and discussed, facilitating the advancement of this area of research. Overall, this study elucidates the potential benefit of using formal models for theory revision and development.
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Affiliation(s)
- Arodi Farrera
- Mathematical Modeling of Social Systems DepartmentInstitute for Research on Applied Mathematics and Systems, National Autonomous University of MexicoMexico CityMexico
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González‐Ruiz JM, Pérez‐Núñez MI, García‐Alfaro MD, Bastir M. How can directional and fluctuating asymmetry help in the prognosis of scoliosis along the course of the condition? J Anat 2021; 239:1400-1408. [PMID: 34263453 PMCID: PMC8602023 DOI: 10.1111/joa.13509] [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: 02/10/2021] [Revised: 06/24/2021] [Accepted: 06/25/2021] [Indexed: 12/21/2022] Open
Abstract
Fluctuating asymmetry (FA) is an indicator of developmental instability referred to random deviations from mean asymmetry. That average asymmetry is the directional asymmetry (DA), which, in the particular case of adolescent idiopathic scoliosis (AIS), corresponds to a right thoracic and left lumbar curves. Investigating the presence of FA and DA in AIS has never been done, and it is a key element of the pathophysiology of the scoliotic condition. Thirty-six X-rays of patients with AIS were digitized and analysed using Geometric Morphometric analyses to test for both statistical effects. The individual FA score for each patient was calculated using Procrustes ANOVA and a methodology based on the components of shape was used to estimate the individual DA score. DA is a stronger effect than FA (2.12 to 1), as it has been found in other clinical conditions. The individual DA score, with an effect size of 0.58, is a better predictor of the Cobb angle than FA score. The methodology presented in this paper to estimate DA score is a valid approach in the study of asymmetries in AIS. FA should be correlated in future studies with environmental covariates to serve as a variable in the medical prognosis, while DA will serve as a good predictor of the Cobb angle during the course of the condition, avoiding the abuse of X-rays. This potential use of DA should be tested on 3D shape due to the three-dimensional clinical presentation of AIS.
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Affiliation(s)
- José María González‐Ruiz
- Virtual Morphology LabMuseo Nacional de Ciencias Naturales – Consejo Superior de Investigaciones CientíficasMadridSpain
| | - María Isabel Pérez‐Núñez
- Department of Orthopedic Surgery and TraumatologyUniversity Hospital of ValdecillaUniversity of CantabriaSantanderSpain
| | - Mª Dolores García‐Alfaro
- Department of Orthopedic Surgery and TraumatologyUniversity Hospital of ValdecillaUniversity of CantabriaSantanderSpain
| | - Markus Bastir
- Virtual Morphology LabMuseo Nacional de Ciencias Naturales – Consejo Superior de Investigaciones CientíficasMadridSpain
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López-Aguirre C, Hand SJ, Koyabu D, Tu VT, Wilson LAB. Prenatal Developmental Trajectories of Fluctuating Asymmetry in Bat Humeri. Front Cell Dev Biol 2021; 9:639522. [PMID: 34124034 PMCID: PMC8187808 DOI: 10.3389/fcell.2021.639522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 04/14/2021] [Indexed: 11/22/2022] Open
Abstract
Fluctuating asymmetry (random fluctuations between the left and right sides of the body) has been interpreted as an index to quantify both the developmental instabilities and homeostatic capabilities of organisms, linking the phenotypic and genotypic aspects of morphogenesis. However, studying the ontogenesis of fluctuating asymmetry has been limited to mostly model organisms in postnatal stages, missing prenatal trajectories of asymmetry that could better elucidate decoupled developmental pathways controlling symmetric bone elongation and thickening. In this study, we quantified the presence and magnitude of asymmetry during the prenatal development of bats, focusing on the humerus, a highly specialized bone adapted in bats to perform under multiple functional demands. We deconstructed levels of asymmetry by measuring the longitudinal and cross-sectional asymmetry of the humerus using a combination of linear measurements and geometric morphometrics. We tested the presence of different types of asymmetry and calculated the magnitude of size-controlled fluctuating asymmetry to assess developmental instability. Statistical support for the presence of fluctuating asymmetry was found for both longitudinal and cross-sectional asymmetry, explaining on average 16% of asymmetric variation. Significant directional asymmetry accounted for less than 6.6% of asymmetric variation. Both measures of fluctuating asymmetry remained relatively stable throughout ontogeny, but cross-sectional asymmetry was significantly different across developmental stages. Finally, we did not find a correspondence between developmental patterns of longitudinal and cross-sectional asymmetry, indicating that processes promoting symmetrical bone elongation and thickening work independently. We suggest various functional pressures linked to newborn bats’ ecology associated with longitudinal (altricial flight capabilities) and cross-sectional (precocial clinging ability) developmental asymmetry differentially. We hypothesize that stable magnitudes of fluctuating asymmetry across development could indicate the presence of developmental mechanisms buffering developmental instability.
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Affiliation(s)
- Camilo López-Aguirre
- Department of Anthropology, University of Toronto Scarborough, Toronto, ON, Canada.,Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Suzanne J Hand
- Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Daisuke Koyabu
- Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong.,Research and Development Center for Precision Medicine, University of Tsukuba, Tsukuba, Japan
| | - Vuong Tan Tu
- Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, Hanoi, Vietnam.,Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Laura A B Wilson
- Earth and Sustainability Science Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia.,School of Archaeology and Anthropology, The Australian National University, Canberra, ACT, Australia
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Oxilia G, Menghi Sartorio JC, Bortolini E, Zampirolo G, Papini A, Boggioni M, Martini S, Marciani F, Arrighi S, Figus C, Marciani G, Romandini M, Silvestrini S, Pedrosi ME, Mori T, Riga A, Kullmer O, Sarig R, Fiorenza L, Giganti M, Sorrentino R, Belcastro MG, Cecchi JM, Benazzi S. Exploring directional and fluctuating asymmetry in the human palate during growth. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 175:847-864. [PMID: 33973654 PMCID: PMC8360102 DOI: 10.1002/ajpa.24293] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 03/23/2021] [Accepted: 04/09/2021] [Indexed: 01/20/2023]
Abstract
Objectives Palate morphology is constantly changing throughout an individual's lifespan, yet its asymmetry during growth is still little understood. In this research, we focus on the study of palate morphology by using 3D geometric morphometric approaches to observe changes at different stages of life, and to quantify the impact of directional and fluctuating asymmetry on different areas at different growth stages. Materials and Methods The sample consists of 183 individuals (1–72 years) from two identified human skeletal collections of 19th and early 20th Century Italian contexts. A 3D‐template of 41 (semi)landmarks was applied on digital palate models to observe morphological variation during growth. Results Asymmetrical components of the morphological structure appears multidirectional on the entire palate surface in individuals <2 years old and become oriented (opposite bilateral direction) between 2 and 6 years of age. Specifically, directional asymmetry differentially impacts palate morphology at different stages of growth. Both the anterior and posterior palate are affected by mild alterations in the first year of life, while between 2 and 6 years asymmetry is segregated in the anterior area, and moderate asymmetry affects the entire palatal surface up to 12 years of age. Our results show that stability of the masticatory system seems to be reached around 13–35 years first by females and then males. From 36 years on both sexes show similar asymmetry on the anterior area. Regarding fluctuating asymmetry, inter‐individual variability is mostly visible up to 12 years of age, after which only directional trends can be clearly observed at a group level. Discussion Morphological structure appears instable during the first year of life and acquires an opposite asymmetric bilateral direction between 2 and 6 years of age. This condition has been also documented in adults; when paired with vertical alteration, anterior/posterior asymmetry seems to characterize palate morphology, which is probably due to mechanical factors during the lifespan. Fluctuating asymmetry is predominant in the first period of life due to a plausible relationship with the strength of morphological instability of the masticatory system. Directional asymmetry, on the other hand, shows that the patterning of group‐level morphological change might be explained as a functional response to differential inputs (physiological forces, nutritive and non‐nutritive habits, para‐masticatory activity as well as the development of speech) in different growth stages. This research has implications with respect to medical and evolutionary fields. In medicine, palate morphology should be considered when planning orthodontic and surgical procedures as it could affect the outcome. As far as an evolutionary perspective is concerned the dominance of directional asymmetries in the masticatory system could provide information on dietary and cultural habits as well as pathological conditions in our ancestors.
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Affiliation(s)
- Gregorio Oxilia
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Jessica C Menghi Sartorio
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy.,Department of Enterprise Engineering, "Mario Lucertini" - Tor Vergata University, Rome, Italy
| | - Eugenio Bortolini
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Giulia Zampirolo
- Section for Evolutionary Genomics Øster Farimagsgade, University of Copenhagen, København, Denmark
| | - Andrea Papini
- Dentist's Surgery, via Walter Tobagi 35, Prato, 59100, Italy
| | - Marco Boggioni
- Dentist's Surgery, via D'Andrade 34/207, Genoa Sestri Ponente, 16154, Italy
| | - Sergio Martini
- Dental Lab Technician, via Milani, 1, Verona, 37124, Italy
| | - Filippo Marciani
- Dentist's Surgery, Studio Dentistico Marciani Dr. Filippo, Via Romagnoli, 14, Lanciano, 66034, Italy
| | - Simona Arrighi
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Carla Figus
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Giulia Marciani
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Matteo Romandini
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Sara Silvestrini
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy
| | - Maria Elena Pedrosi
- Department of Biological, Geological and Environmental Sciences-, BiGeA University of Bologna, Bologna, Italy
| | - Tommaso Mori
- Department of Biology, University of Florence, Florence, Italy
| | - Alessandro Riga
- Department of Biology, University of Florence, Florence, Italy
| | - Ottmar Kullmer
- Senckenberg Research Institute, Senckenberganlage 25, Frankfurt am Main, 60325, Germany.,Department of Paleobiology and Environment, Institute of Ecology, Evolution, and Diversity, Johann Wolfgang Goethe University, Frankfurt, Germany
| | - Rachel Sarig
- Department of Oral biology, The Goldschleger School of Dental Medicine and the Dan David Center for Human Evolution, the Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel
| | - Luca Fiorenza
- Monash Biomedicine Discovery Institute, Department of Anatomy and Developmental Biology, Monash University, Melbourne, Victoria, Australia
| | - Melchiore Giganti
- Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy.,Radiology University Unit, University Hospital, Ferrara, Italy
| | - Rita Sorrentino
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy.,Department of Biological, Geological and Environmental Sciences-, BiGeA University of Bologna, Bologna, Italy
| | - Maria Giovanna Belcastro
- Department of Biological, Geological and Environmental Sciences-, BiGeA University of Bologna, Bologna, Italy
| | | | - Stefano Benazzi
- Department of Cultural Heritage, University of Bologna, Ravenna, Italy.,Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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