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Abulnoor BA, Attia MH, Konigsberg IR, Konigsberg LW. TestDimorph: An R package for analysis of interpopulation sexual dimorphism differences using summary statistics. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 182:487-498. [PMID: 37694912 DOI: 10.1002/ajpa.24842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 08/08/2023] [Accepted: 08/13/2023] [Indexed: 09/12/2023]
Abstract
OBJECTIVE The degree of sexual dimorphism in certain traits between males and females differ from one sample to another. Although trait differences by sex are often reported in bioanthropological research, few studies test for statistical significance or make raw data available. TestDimorph is the first R package dedicated to testing and comparing the degree of sexual dimorphism among different samples by leveraging summary statistics. MATERIALS AND METHODS We provide two approaches of analysis of inter-sample differences in degree of sexual dimorphism: univariate and multivariate for two or more samples. The methods follow upon publications primarily from the AJBA. Within-sex size variability between samples is compared using one-way ANOVA followed by control for multiple pairwise comparisons. In addition, we compute the overlapping area between the density functions of two normal distributions from the mixture intersection index or the non-overlapping area using the dissimilarity index as well as Hedges' g with inferential support using the 95% confidence interval. Finally, we use a multivariate analysis of differences in patterning of sexual dimorphism between samples. RESULTS We demonstrate various results from applying TestDimorph functions to data supplied with the package. DISCUSSION The package has many features including functionality for working with summary statistics, simulating data from summary statistics, and the extraction of summary statistics from raw data, so that the entire analysis can be performed through the package.
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Affiliation(s)
- Bassam A Abulnoor
- Fixed prosthodontics, Faculty of dentistry, Ain Shams University, Cairo, Egypt
| | - MennattAllah Hassan Attia
- Forensic medicine and clinical toxicology, Faculty of medicine- Alexandria University, Alexandria, Egypt
| | - Iain R Konigsberg
- Department of Biomedical Informatics, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Lyle W Konigsberg
- Department of Anthropology, University of Illinois, at Urbana - Champaign, Urbana, Illinois, USA
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2
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Braun S, Schwendener N, Kanz F, Lösch S, Milella M. What we see is what we touch? Sex estimation on the pelvis in virtual anthropology. Int J Legal Med 2023; 137:1839-1852. [PMID: 37336820 PMCID: PMC10567926 DOI: 10.1007/s00414-023-03034-w] [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: 02/27/2023] [Accepted: 05/29/2023] [Indexed: 06/21/2023]
Abstract
BACKGROUND Computed tomography (CT) scans are a convenient means to study 3D reconstructions of bones. However, errors associated with the different nature of the observation, e.g. visual and tactile (on dry bone) versus visual only (on a screen) have not been thoroughly investigated. MATERIALS AND METHODS We quantified the errors between modalities for sex estimation protocols of nonmetric (categorical and ordinal) and metric data, using 200 dry pelves of archaeological origin and the CT reconstructions of the same bones. In addition, we 3D surface scanned a subsample of 39 pelves to compare observations with dry bone and CT data. We did not focus on the sex estimation accuracy but solely on the consistency of the scoring, hence, the interchangeability of the modalities. RESULTS Metric data yielded the most consistent results. Among the nonmetric protocols, ordinal data performed better than categorical data. We applied a slightly modified description for the trait with the highest errors and grouped the traits according to consistency and availability in good, intermediate, and poor. DISCUSSION The investigated modalities were interchangeable as long as the trait definition was not arbitrary. Dry bone (gold standard) performed well, and CT and 3D surface scans performed better. We recommend researchers test their affinity for using virtual modalities. Future studies could use our consistency analysis and combine the best traits, validating their accuracy on various modalities.
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Affiliation(s)
- Sandra Braun
- Department of Physical Anthropology, Institute of Forensic Medicine, University of Bern, Murtenstrasse 24-28, 3008, Bern, Switzerland.
| | - Nicole Schwendener
- Department of Forensic Medicine and Imaging, Institute of Forensic Medicine, University of Bern, Bern, Switzerland
| | - Fabian Kanz
- Forensic Anthropology Unit, Center for Forensic Medicine, Medical University of Vienna, Vienna, Austria
| | - Sandra Lösch
- Department of Physical Anthropology, Institute of Forensic Medicine, University of Bern, Murtenstrasse 24-28, 3008, Bern, Switzerland
| | - Marco Milella
- Department of Physical Anthropology, Institute of Forensic Medicine, University of Bern, Murtenstrasse 24-28, 3008, Bern, Switzerland
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Grunstra NDS, Betti L, Fischer B, Haeusler M, Pavlicev M, Stansfield E, Trevathan W, Webb NM, Wells JCK, Rosenberg KR, Mitteroecker P. There is an obstetrical dilemma: Misconceptions about the evolution of human childbirth and pelvic form. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 181:535-544. [PMID: 37353889 PMCID: PMC10952510 DOI: 10.1002/ajpa.24802] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2023] [Revised: 05/27/2023] [Accepted: 06/11/2023] [Indexed: 06/25/2023]
Abstract
Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been termed the "obstetrical dilemma." Recently, there has been a growing tendency among some anthropologists to question the difficulty of human childbirth and its evolutionary origin in an antagonistic selective regime. Partly, this stems from the motivation to combat increasing pathologization and overmedicalization of childbirth in industrialized countries. Some authors have argued that there is no obstetrical dilemma at all, and that the difficulty of childbirth mainly results from modern lifestyles and inappropriate and patriarchal obstetric practices. The failure of some studies to identify biomechanical and metabolic constraints on pelvic dimensions is sometimes interpreted as empirical support for discarding an obstetrical dilemma. Here we explain why these points are important but do not invalidate evolutionary explanations of human childbirth. We present robust empirical evidence and solid evolutionary theory supporting an obstetrical dilemma, yet one that is much more complex than originally conceived in the 20th century. We argue that evolutionary research does not hinder appropriate midwifery and obstetric care, nor does it promote negative views of female bodies. Understanding the evolutionary entanglement of biological and sociocultural factors underlying human childbirth can help us to understand individual variation in the risk factors of obstructed labor, and thus can contribute to more individualized maternal care.
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Affiliation(s)
- N. D. S. Grunstra
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
- Mammal CollectionNatural History Museum ViennaViennaAustria
| | - L. Betti
- School of Life and Health SciencesUniversity of RoehamptonLondonUK
| | - B. Fischer
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - M. Haeusler
- Institute of Evolutionary MedicineUniversity of ZurichZurichSwitzerland
| | - M. Pavlicev
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - E. Stansfield
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
| | - W. Trevathan
- School for Advanced ResearchSanta FeNew MexicoUSA
| | - N. M. Webb
- Institute of Evolutionary MedicineUniversity of ZurichZurichSwitzerland
- Institute of Archaeological Sciences, Senckenberg Centre for Human Evolution and PalaeoenvironmentEberhard‐Karls University of TübingenTübingenGermany
| | - J. C. K. Wells
- UCL Great Ormond Street Institute of Child Health, Population, Policy and Practice Research and Teaching ProgrammeChildhood Nutrition Research CentreLondonUK
| | - K. R. Rosenberg
- Department of AnthropologyUniversity of DelawareNewarkDelawareUSA
| | - P. Mitteroecker
- Department of Evolutionary Biology, Unit for Theoretical BiologyUniversity of ViennaViennaAustria
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4
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Kubicka AM. Changes in plasticity of the pelvic girdle from infancy to late adulthood in Homo sapiens. Sci Rep 2023; 13:9698. [PMID: 37322042 PMCID: PMC10272276 DOI: 10.1038/s41598-023-36703-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 06/08/2023] [Indexed: 06/17/2023] Open
Abstract
Previous research on the effects of body mass on the pelvic girdle focused mostly on adult females and males. Because the ontogenetic plasticity level in the pelvis remains largely unknown, this study investigated how the association between body mass index (BMI) and pelvic shape changes during development. It also assessed how the large variation in pelvic shape could be explained by the number of live births in females. Data included CT scans of 308 humans from infancy to late adulthood with known age, sex, body mass, body stature, and the number of live births (for adult females). 3D reconstruction and geometric morphometrics was used to analyze pelvic shape. Multivariate regression showed a significant association between BMI and pelvic shape in young females and old males. The association between the number of live births and pelvic shape in females was not significant. Less plasticity in pelvic shape in adult females than during puberty, perhaps reflects adaptation to support the abdominopelvic organs and the fetus during pregnancy. Non-significant susceptibility to BMI in young males may reflect bone maturation accelerated by excessive body mass. Hormonal secretion and biomechanical loading associated with pregnancy may not have a long-term effect on the pelvic morphology of females.
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Affiliation(s)
- Anna Maria Kubicka
- Department of Zoology, Poznań University of Life Sciences, Wojska Polskiego 71C, 60-625, Poznań, Poland.
- PaleoFED Team, Département Homme et Environnement, Muséum National d'Histoire Naturelle. Musée de l'Homme, UMR 7194, CNRS, Place du Trocadéro 17, 75016, Paris, France.
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5
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Antón SC, Middleton ER. Making meaning from fragmentary fossils: Early Homo in the Early to early Middle Pleistocene. J Hum Evol 2023; 179:103307. [PMID: 37030994 DOI: 10.1016/j.jhevol.2022.103307] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 11/16/2022] [Accepted: 11/27/2022] [Indexed: 04/10/2023]
Abstract
In celebration of the 50th anniversary of the Journal of Human Evolution, we re-evaluate the fossil record for early Homo (principally Homo erectus, Homo habilis, and Homo rudolfensis) from early diversification and dispersal in the Early Pleistocene to the ultimate demise of H. erectus in the early Middle Pleistocene. The mid-1990s marked an important historical turning point in our understanding of early Homo with the redating of key H. erectus localities, the discovery of small H. erectus in Asia, and the recovery of an even earlier presence of early Homo in Africa. As such, we compare our understanding of early Homo before and after this time and discuss how the order of fossil discovery and a focus on anchor specimens has shaped, and in many ways biased, our interpretations of early Homo species and the fossils allocated to them. Fragmentary specimens may counter conventional wisdom but are often overlooked in broad narratives. We recognize at least three different cranial and two or three pelvic morphotypes of early Homo. Just one postcranial morph aligns with any certainty to a cranial species, highlighting the importance of explicitly identifying how we link specimens together and to species; we offer two ways of visualizing these connections. Chronologically and morphologically H. erectus is a member of early Homo, not a temporally more recent species necessarily evolved from either H. habilis or H. rudolfensis. Nonetheless, an ancestral-descendant notion of their evolution influences expectations around the anatomy of missing elements, especially the foot. Weak support for long-held notions of postcranial modernity in H. erectus raises the possibility of alternative drivers of dispersal. New observations suggest that the dearth of faces in later H. erectus may mask taxonomic diversity in Asia and suggest various later mid-Pleistocene populations could derive from either Asia or Africa. Future advances will rest on the development of nuanced ways to affiliate fossils, greater transparency of implicit assumptions, and attention to detailed life history information for comparative collections; all critical pursuits for future research given the great potential they have to enrich our evolutionary reconstructions for the next fifty years and beyond.
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Affiliation(s)
- Susan C Antón
- Center for the Study of Human Origins, Department of Anthropology, New York University, NY, NY 10003, USA.
| | - Emily R Middleton
- Department of Anthropology, University of Wisconsin-Milwaukee, WI 53211, USA
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Anthropometric study using three-dimensional pelvic CT scan in sex determination among adult Indonesian population. Forensic Sci Med Pathol 2023; 19:24-33. [PMID: 36103007 PMCID: PMC10014651 DOI: 10.1007/s12024-022-00526-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2022] [Indexed: 10/14/2022]
Abstract
This study aims to determine pelvic anthropometry characteristics and logistic regression formula for adult sex identification obtained from adult three-dimensional pelvic computed tomography images. This study was an observational analytical study with retrospective regression and cross-sectional approach. The population was all patients at Radiology Installation of Dr. Soetomo General Academic Hospital as referral hospital in East Indonesian region, from September to December 2019 who underwent 3D pelvic CT examination. Then, age distribution and pelvic measurements data were obtained. In this case, statistical analysis was conducted for all the data obtained. A number of 204 samples were included in this study. All radiologic components were also significantly different between sexes (p < 0.05) except for transverse diameter of sacral segment (p = 0.180). Moreover, the conjugate pelvic inlet diameter (CPID), the left innominate height (LIH), and sub pubic angle (SPA) showed significant values for regression formula to determine an adult's sex using 3D pelvic CT. The calculation result > 0 is a prediction for female while < 0 is a prediction for male. From logistic regression model calculation, a high validity value (91.05%) was found with 100% sensitivity to identify male sex and 81.1% specificity to identify female sex. There were differences on radiometric variable characteristics in pelvic anthropometric study among adult Indonesians at Dr. Soetomo General Academic Hospital, Surabaya. The estimated values of pelvic measurements using 3D CT images could develop a pelvic model with a regression formula with high accuracy value using CPID, LIH, and SPA values.
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Evaluation of the obturator foramen as a sex assessment trait. Forensic Sci Med Pathol 2022:10.1007/s12024-022-00514-0. [PMID: 35960449 DOI: 10.1007/s12024-022-00514-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/29/2022] [Indexed: 10/15/2022]
Abstract
Correctly assessing sex from skeletal remains is one of the main elements of creating a biological profile. Many traits allow for this, the obturator foramen being one. However, research on its accuracy has provided mixed results. This study examines the obturator foramen using a 5-point grading scale to assess the degree of sexual dimorphism in four known age and sex skeletal collections from the UK and South Africa. Overall, sexual dimorphism was found in the obturator foramen when using the new scoring system; however, accuracies for correct sex classification ranged from ~ 46 to ~ 75%. Considering its wide range in accuracy rates across the four samples and difficulty in identifying the subtle changes in morphology, the obturator foramen should only be used as part of a multifactorial assessment of sex.
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Haeusler M, Grunstra ND, Martin RD, Krenn VA, Fornai C, Webb NM. The obstetrical dilemma hypothesis: there's life in the old dog yet. Biol Rev Camb Philos Soc 2021; 96:2031-2057. [PMID: 34013651 PMCID: PMC8518115 DOI: 10.1111/brv.12744] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 05/06/2021] [Accepted: 05/10/2021] [Indexed: 12/17/2022]
Abstract
The term 'obstetrical dilemma' was coined by Washburn in 1960 to describe the trade-off between selection for a larger birth canal, permitting successful passage of a big-brained human neonate, and the smaller pelvic dimensions required for bipedal locomotion. His suggested solution to these antagonistic pressures was to give birth prematurely, explaining the unusual degree of neurological and physical immaturity, or secondary altriciality, observed in human infants. This proposed trade-off has traditionally been offered as the predominant evolutionary explanation for why human childbirth is so challenging, and inherently risky, compared to that of other primates. This perceived difficulty is likely due to the tight fit of fetal to maternal pelvic dimensions along with the convoluted shape of the birth canal and a comparatively low degree of ligamentous flexibility. Although the ideas combined under the obstetrical dilemma hypothesis originated almost a century ago, they have received renewed attention and empirical scrutiny in the last decade, with some researchers advocating complete rejection of the hypothesis and its assumptions. However, the hypothesis is complex because it presently captures several, mutually non-exclusive ideas: (i) there is an evolutionary trade-off resulting from opposing selection pressures on the pelvis; (ii) selection favouring a narrow pelvis specifically derives from bipedalism; (iii) human neonates are secondarily altricial because they are born relatively immature to ensure that they fit through the maternal bony pelvis; (iv) as a corollary to the asymmetric selection pressure for a spacious birth canal in females, humans evolved pronounced sexual dimorphism of pelvic shape. Recently, the hypothesis has been challenged on both empirical and theoretical grounds. Here, we appraise the original ideas captured under the 'obstetrical dilemma' and their subsequent evolution. We also evaluate complementary and alternative explanations for a tight fetopelvic fit and obstructed labour, including ecological factors related to nutrition and thermoregulation, constraints imposed by the stability of the pelvic floor or by maternal and fetal metabolism, the energetics of bipedalism, and variability in pelvic shape. This reveals that human childbirth is affected by a complex combination of evolutionary, ecological, and biocultural factors, which variably constrain maternal pelvic form and fetal growth. Our review demonstrates that it is unwarranted to reject the obstetrical dilemma hypothesis entirely because several of its fundamental assumptions have not been successfully discounted despite claims to the contrary. As such, the obstetrical dilemma remains a tenable hypothesis that can be used productively to guide evolutionary research.
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Affiliation(s)
- Martin Haeusler
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
| | - Nicole D.S. Grunstra
- Konrad Lorenz Institute (KLI) for Evolution and Cognition ResearchMartinstrasse 12Klosterneuburg3400Austria
- Department of Evolutionary BiologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
- Mammal CollectionNatural History Museum ViennaBurgring 7Vienna1010Austria
| | - Robert D. Martin
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- The Field Museum1400 S Lake Shore DrChicagoIL60605U.S.A.
| | - Viktoria A. Krenn
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Cinzia Fornai
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Department of Evolutionary AnthropologyUniversity of ViennaUniversity Biology Building (UBB), Carl Djerassi Platz 1Vienna1030Austria
| | - Nicole M. Webb
- Institute of Evolutionary MedicineUniversity of ZurichWinterthurerstrasse 190Zürich8057Switzerland
- Senckenberg Research Institute and Natural History Museum FrankfurtSenckenberganlage 25Frankfurt am Main60325Germany
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Cox SL. A geometric morphometric assessment of shape variation in adult pelvic morphology. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 176:652-671. [PMID: 34528241 DOI: 10.1002/ajpa.24399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 06/13/2021] [Accepted: 07/29/2021] [Indexed: 12/16/2022]
Abstract
OBJECTIVES In humans, the pelvis is the most sexually dimorphic skeletal element and is often utilized in aging and sexing remains. The pelvis has become greatly relied upon in anthropological research (e.g., forensics, demographics, obstetrics, evolutionary history); however, pelvis morphology is highly variable, and very little is known about the nature, sources, patterning, and interpretation of this variation. This study aims to quantify pelvis shape variation, document sexual shape variation, and estimate the plasticity of morphology. This will ultimately give greater ability to interpret modern, archaeological, and evolutionary patterns to gain deeper insight into processes which shape human anatomy. MATERIALS AND METHODS Using a sample of 129 Medieval Danish skeletons, shape variation is documented in the greater sciatic notch (GSN), iliac crest (IC), arcuate line (AL), and sub-pubic angle (SPA) using 3D geometric morphometrics. The landmarking method applied here has the advantage of being applicable to fragmentary remains, rather than requiring whole bones. This allows it to be easily applied to archaeological samples and for the interpretation of separate bone features. Differences in shape were statistically analyzed by principle component analysis, linear discriminate analysis, and morphological disparity. Relationships between maximum femur length, body mass, and shape centroid size were also test by allometric regression. RESULTS Results quantify the sexual dimorphism and shape variation present in these features. The GSN shape is the most variable, while the AL is the least. Similarly, the IC is the only feature which shows almost no dimorphism in shape, and instead best reflects lifestyle/activity patterns. Evidence of dimorphism in the IC is likely a result of cultural labor patterns rather than genetic and hormonal influence. Finally, the shapes of the GSN, AL, and SPA are more related to body mass than to femur length, such that individuals with increased mass exhibit more classically "male" shapes and those with less mass have more "female" shapes. DISCUSSION The results have important implications for the evolution of pelvic anatomy, and sexual dimorphism, but also highlight the plasticity inherent in pelvic morphology. Analyzing pelvis features separately in a clearly defined, relatively genetically homogenous population gives insight into the determinants of bone morphology, which are not readily observable by other means. The relationship between body mass and shape suggests dimorphism in body size and composition may affect bone shape.
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Affiliation(s)
- Samantha L Cox
- Department of Genetics, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,Physical Anthropology, Penn Museum, University of Pennsylvania, Philadelphia, Pennsylvania, USA.,University of Cambridge, Department of Archaeology, Cambridge, UK
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10
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Frémondière P, Thollon L, Marchal F. Pelvic and neonatal size correlations in light of evolutionary hypotheses. Am J Hum Biol 2021; 34:e23619. [PMID: 34028115 DOI: 10.1002/ajhb.23619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 04/26/2021] [Accepted: 05/03/2021] [Indexed: 12/13/2022] Open
Abstract
OBJECTIVE This study aimed to analyze the correlations between maternal size, neonatal size, and gestational variables. METHODS Our sample comprises 131 mother-infant dyads. We investigated correlations between five neonatal traits (gestational age, birthweight, head, suboccipito-brematic, and abdominal girths), three maternal traits (height, BMI, and uterus height), and three pelvic variables (conjugate, inter-spinous diameters, and sub-pubic angle) using computed tomography pelvimetry. RESULTS We found that the five neonatal traits were significantly intercorrelated. BMI was not correlated with neonatal traits while maternal height was correlated with birthweight, suboccipito-brematic, and abdominal girth. In the multiple regression models, gestational age was correlated with birthweight, head, and abdominal girth. Among the neonatal and pelvimetry correlations, conjugate diameter was slightly correlated with suboccipito-bregmatic girth, but inter-spinous and sub-pubic angle were not correlated with neonatal traits. Uterus height predicted all neonatal variables, but it was not correlated with gestational age. DISCUSSION Our results suggest that fetal growth is shaped by maternal phenotype rather than external ecological factors. The association of the inlet size with suboccipito-bregmatic girth reflects the tight fit between the neonatal brain and the maternal pelvis dimensions, an adaptation that would reduce the risk of cephalo-pelvic disproportion, while the absence of tight fit at the midplane and outlet could be due to the effect of the pelvic relaxation. Uterus distention is not the only mechanism involved in the initiation of parturition. Birth and pregnancy are complex processes and we suggest that maternal-neonatal associations are the result of a combination of multiple obstetric tradeoffs.
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Affiliation(s)
- Pierre Frémondière
- Aix Marseille Univ, School of Midwifery, Faculty of Medical and Paramedical Sciences, Marseille, France.,Aix Marseille Univ, CNRS, EFS, ADES, Marseille, France
| | - Lionel Thollon
- Applied Biomechanics Laboratory (UMR-T24), Marseille, France
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11
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Fischer B, Grunstra NDS, Zaffarini E, Mitteroecker P. Sex differences in the pelvis did not evolve de novo in modern humans. Nat Ecol Evol 2021; 5:625-630. [PMID: 33767411 DOI: 10.1038/s41559-021-01425-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 02/24/2021] [Indexed: 01/31/2023]
Abstract
It is commonly assumed that the strong sexual dimorphism of the human pelvis evolved for delivering the relatively large human foetuses. Here we compare pelvic sex differences across modern humans and chimpanzees using a comprehensive geometric morphometric approach. Even though the magnitude of sex differences in pelvis shape was two times larger in humans than in chimpanzees, we found that the pattern is almost identical in the two species. We conclude that this pattern of pelvic sex differences did not evolve de novo in modern humans and must have been present in the common ancestor of humans and chimpanzees, and thus also in the extinct Homo species. We further suggest that this shared pattern was already present in early mammals and propose a hypothesis of facilitated variation as an explanation: the conserved mammalian endocrine system strongly constrains the evolution of the pattern of pelvic differences but enables rapid evolutionary change of the magnitude of sexual dimorphism, which in turn facilitated the rapid increase in hominin brain size.
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Affiliation(s)
- Barbara Fischer
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Vienna, Austria.
| | - Nicole D S Grunstra
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Vienna, Austria.,Konrad Lorenz Institute for Evolution and Cognition Research, Klosterneuburg, Austria.,Mammal Collection, Natural History Museum Vienna, Vienna, Austria
| | - Eva Zaffarini
- Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada
| | - Philipp Mitteroecker
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Vienna, Austria.,Konrad Lorenz Institute for Evolution and Cognition Research, Klosterneuburg, Austria
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12
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Milella M, Franklin D, Belcastro MG, Cardini A. Sexual differences in human cranial morphology: Is one sex more variable or one region more dimorphic? Anat Rec (Hoboken) 2021; 304:2789-2810. [PMID: 33773067 DOI: 10.1002/ar.24626] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 02/25/2021] [Accepted: 03/01/2021] [Indexed: 01/06/2023]
Abstract
The quantification of cranial sexual dimorphism (CSD) among modern humans is relevant in evolutionary studies of morphological variation and in a forensic context. Despite the abundance of quantitative studies of CSD, few have specifically examined intra-sex variability. Here we quantify CSD in a geographically homogeneous sample of adult crania, which includes Italian individuals from the 19th and 20th centuries. Cranial morphology is described with 92 3D landmarks analyzed using Procrustean geometric morphometrics (PGMM). Size and shape variables are used to compare morphological variance between sexes in the whole cranium and four individual regions. The same variables, plus Procrustes form, are used to quantify average sex differences and explore classification accuracy. Our results indicate that: (a) as predicted by Wainer's rule, males present overall more variance in size and shape, albeit this is statistically significant only for total cranial size; (b) differences between sexes are dominated by size and to a lesser extent by Procrustes form; (c) shape only accounts for a minor proportion of variance; (d) the cranial base shows almost no dimorphism for shape; and (e) facial Procrustes form is the most accurate predictor of skeletal sex. Overall, this study suggests developmental factors underlying differences in CSD among cranial regions; stresses the need for population-specific models that describe craniofacial variation as the basis for models that facilitate the estimation of sex in unidentified skeletal remains; and provides one of the first confirmations of "Wainer's rule" in relation to sexual dimorphism in mammals specific to the human cranium.
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Affiliation(s)
- Marco Milella
- Department of Physical Anthropology, Institute of Forensic Medicine, University of Bern, Bern, Switzerland
| | - Daniel Franklin
- Centre for Forensic Anthropology, The University of Western Australia, Crawley, Western Australia, Australia
| | - Maria Giovanna Belcastro
- Department of Biological, Geological and Environmental Sciences, Alma Mater Studiorum, University of Bologna, Bologna, Italy
| | - Andrea Cardini
- Centre for Forensic Anthropology, The University of Western Australia, Crawley, Western Australia, Australia.,Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, Modena, Italy
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Waxenbaum EB, Feiler ME. Influence of climatic stress on nonmetric sexually dimorphic features of the skull and pelvis. Am J Hum Biol 2020; 33:e23559. [PMID: 33377211 DOI: 10.1002/ajhb.23559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Revised: 11/05/2020] [Accepted: 12/11/2020] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVES Human sexual dimorphism is frequently assessed through skull and pelvic size and shape. Researchers suggest that climatic variation and the associated stress may be significant factors in sexual dimorphism's etiology. However, little research has specifically investigated climatic effects on nonmetric skeletal indicators of sex. To further appreciate the plasticity of human biology, a comparative study of standard skull and pelvic nonmetric sex indicators is presented. METHODS A Native Alaskan archeological sample (n = 104) and a component of the Terry collection (n = 99) represent populations originating from different climatic environments in recent history. These sex-balanced groups are compared through Tukey-Kramer's method and Greene's t-test to determine any variation in degree of sexual dimorphism within and between samples. RESULTS The results reinforce the complex and multifaceted relationship between climate and sexual dimorphism. The Terry sample demonstrated a greater degree of sexual dimorphism with statistically significant differences in robusticity of the mastoid process and nuchal crest compared with the Native Alaskans. A more "male" morphotype and reduced dimorphism are appreciated in the pelves of Native Alaskans than the Terry sample. CONCLUSIONS This research highlights a reduction in sexual dimorphism in populations under greater climatic stress and contributes to the production of more accurate skeletal assessments in future investigations. Discussion of confounding factors suggest more research is necessary to untangle climate and human morphology's complex relationship. This study contributes to a greater appreciation of human biological plasticity, ecogeographic variation, and the evolution of modern human diversity.
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Affiliation(s)
- Erin B Waxenbaum
- Department of Anthropology, Northwestern University, Evanston, Illinois, USA
| | - Maria E Feiler
- Department of Anthropology, Northwestern University, Evanston, Illinois, USA
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Uy J, Hawks J, VanSickle C. Sexual dimorphism of the relationship between the gut and pelvis in humans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 173:130-140. [PMID: 32519366 DOI: 10.1002/ajpa.24084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 02/04/2020] [Accepted: 05/06/2020] [Indexed: 01/12/2023]
Abstract
OBJECTIVES Obstetric demands have long been considered in the evolution of the pelvis, yet consideration of the interaction of pregnancy, the pelvis, and the gastrointestinal tract (gut) is lacking. Here, we explore sex differences in the relationship of gut volume with body size and pelvic dimensions. MATERIALS AND METHODS Computed tomography (CT) scans of living adult Homo sapiens (46 females and 42 males) were obtained to measure in vivo gut volume (GV) and to extract 3D models of the pelvis. We collected 19 3D landmarks from each pelvis model to acquire pelvic measurements. We used ordinary least squares regression to explore relationships between GV and body weight, stature, and linear pelvic dimensions. RESULTS The gut-pelvis relationship differs between males and females. Females do not exhibit significant statistical correlations between GV and any variable tested. GV correlates with body size and pelvic outlet size in males. GV scales with negative allometry relative to body weight, stature, maximum bi-iliac breadth, inferior transverse outlet breadth, and bispinous distance in males. DISCUSSION The lack of association between GV and body size in females may be due to limits imposed by the anticipation of accommodating a gravid uterus and/or the increased plasticity of the pelvis. The pattern of relationship between GV and the pelvic outlet suggests the role of the bony pelvis in supporting the adominal viscera in females may be small relative to its role in childbirth. We conclude that gut size inference in fossil hominins from skeletal proxies is limited and confounded by sexual dimorphism.
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Affiliation(s)
- Jeanelle Uy
- Department of Anthropology, California State University, Long Beach, California, USA
| | - John Hawks
- Department of Anthropology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, South Africa
| | - Caroline VanSickle
- Department of Anatomy, A.T. Still University Kirksville College of Osteopathic Medicine, 800 W. Jefferson St., Kirksville, Missouri, USA
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15
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Cuzzullin MC, Curate F, Freire AR, Costa ST, Prado FB, Daruge Junior E, Cunha E, Rossi AC. Validation of anthropological measures of the human femur for sex estimation in Brazilians. AUST J FORENSIC SCI 2020. [DOI: 10.1080/00450618.2020.1729411] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
| | - Francisco Curate
- Research Centre for Anthropology and Health, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
| | | | | | | | | | - Eugénia Cunha
- Centre for Functional Ecology, Laboratory of Forensic Sciences, Department of Life Sciences, University of Coimbra, Coimbra, Portugal
- Department of Life Sciences, National Institute of Legal Medicine and Forensic Sciences, Lisbon, Portugal
| | - Ana Cláudia Rossi
- Piracicaba Dental School, University of Campinas - UNICAMP, Piracicaba, Brazil
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d'Oliveira Coelho J, Curate F. CADOES: An interactive machine-learning approach for sex estimation with the pelvis. Forensic Sci Int 2019; 302:109873. [PMID: 31382223 DOI: 10.1016/j.forsciint.2019.109873] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/25/2019] [Accepted: 06/28/2019] [Indexed: 11/29/2022]
Abstract
The pelvis is consistently regarded as the most sexually dimorphic region of the human skeleton, and methods for sex estimation with the pelvic bones are usually very accurate. In this investigation, population-specific osteometric models for the assessment of sex with the pelvis were designed using a dataset provided by J.A. Serra (1938) that included 256 individuals (131 females and 125 males) from the Coimbra Identified Skeletal Collection and 38 metric variables. The models for sex estimation were operationalized through an online application and decision support system, CADOES. Different classification algorithms generated high accuracy models, ranging from 85% to 92%, with only three variables; and from 85.33% to 97.33%, with all 38 variables. CADOES conveys a probabilistic prediction of skeletal sex, as well as a suite of attributes with educational applicability in the fields of human skeletal anatomy and statistics. This study upholds the value of the pelvis for the estimation of skeletal sex and provides models for that can be applied with high accuracy and low bias.
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Affiliation(s)
- João d'Oliveira Coelho
- Institute of Cognitive and Evolutionary Anthropology, University of Oxford, Oxford, United Kingdom; Laboratory of Forensic Anthropology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal.
| | - Francisco Curate
- Laboratory of Forensic Anthropology, Department of Life Sciences, University of Coimbra, Coimbra, Portugal; Research Centre for Anthropology and Health, Department of Life Sciences, University of Coimbra, Portugal
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17
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Robertson HI, Pokotylo DL, Weston DA. Testing landmark redundancy for sex-based shape analysis of the adult human os coxa. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 169:689-703. [PMID: 31155703 DOI: 10.1002/ajpa.23860] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 04/13/2019] [Accepted: 05/13/2019] [Indexed: 12/27/2022]
Abstract
OBJECTIVES To test the individual effectiveness of common landmarks used in sex estimation of whole adult coxal bones in sex-based shape analysis and propose a method to determine how many principal components of sex-based shape to include for discriminant function analysis. METHODS Three-dimensional models (NextEngine desktop laser scanner) of left and right os coxae from 396 individuals (William Bass Skeletal Collection, Forensic Anthropology Centre, University of Tennessee, Knoxville, TN) were subjected to shape analysis using 32 landmarks (Landmark 3.6, Institute for Data Analysis and Visualization). Each landmark was individually removed and subjected to a new principal component analysis to identify the effect omitting a landmark has on PC1/PC2 ordination. Landmarks that poorly discriminated sex-based shape were considered redundant for analysis on sex estimation. RESULTS This study identified 17 landmarks that represent sex-based shape of right and left coxal bones most effectively, these are: the anterior superior iliac spine; posterior superior iliac spine; posterior inferior iliac spine; iliac crest; apex of the auricular surface; greater sciatic notch; ischial spine; superior, inferior and distal points on ischial tuberosity; superior, inferior and midpoint on the symphyseal face; arcuate eminence; ischiopubic ramus; posterosuperior and anterosuperior points on the acetabular rim. The first and second PCs of the 17-landmark configuration correctly predicted sex in 98.5% of cases; better than a 32-landmark configuration (96%) and better than previous landmark studies on whole coxal bone sex-based shape. CONCLUSIONS These 17 landmarks represent more meaningful data for sex-based shape analysis in PC1 and 2 and concentrate meaningful sex-based shape data to the first five PCs that make up over 50% of the total shape variance.
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Affiliation(s)
- Heather I Robertson
- Department of Anthropology, University of British Columbia, Vancouver, British Columbia, Canada
| | - David L Pokotylo
- Department of Anthropology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Darlene A Weston
- Department of Anthropology, University of British Columbia, Vancouver, British Columbia, Canada
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18
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Santos F, Guyomarc'h P, Rmoutilova R, Bruzek J. A method of sexing the human os coxae based on logistic regressions and Bruzek's nonmetric traits. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2019; 169:435-447. [DOI: 10.1002/ajpa.23855] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 04/29/2019] [Accepted: 05/06/2019] [Indexed: 01/15/2023]
Affiliation(s)
- Frédéric Santos
- Université de Bordeaux – CNRS – MCC, UMR 5199 PACEA Pessac France
| | - Pierre Guyomarc'h
- Université Aix Marseille – CNRS – EFS, UMR 7268 ADES Marseille France
| | - Rebeka Rmoutilova
- Université de Bordeaux – CNRS – MCC, UMR 5199 PACEA Pessac France
- Department of Anthropology and Human Genetics, Faculty of ScienceCharles University Prague Czech Republic
| | - Jaroslav Bruzek
- Université de Bordeaux – CNRS – MCC, UMR 5199 PACEA Pessac France
- Department of Anthropology and Human Genetics, Faculty of ScienceCharles University Prague Czech Republic
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19
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Takamuku H. Does obstetric protection apply to small-bodied females?: A comparison between small-bodied Jomon foragers and large-bodied Yayoi agriculturalists in the prehistoric Japanese archipelago. Am J Hum Biol 2019; 31:e23236. [PMID: 30968505 DOI: 10.1002/ajhb.23236] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 01/07/2019] [Accepted: 02/24/2019] [Indexed: 12/19/2022] Open
Abstract
OBJECTIVES This study examined the relationship between maternal pelvic and body size in the transition from the Middle-Final Jomon period (c. 5000-3000 BC) to the Middle Yayoi period (c. 400~200 BC to around AD 1) in Japan. METHODS Eight measurements, including the left hip bone, articulated pelvis, and femur, were taken from Jomon (females: 37, males: 26) and Yayoi skeletal remains (females: 32, males: 29). RESULTS A statistically significant decrease in the anterior diameter of the true pelvic inlet was demonstrated in females from the Jomon to the Yayoi period, but not in males. While significant increases in stature from the Jomon to the Yayoi period were found in both males and females, no significant changes in body mass were seen. The correlation coefficients between true and false pelvic measurements (maximum pelvic height and maximum pelvic breadth) and body size (stature and body mass) suggested few significant relationships between true and false pelvic measurements or body size among the samples, but no significant correlations in small-bodied Jomon females. Results of principal component analysis using the log-size and log-shape variables suggested that the true pelvic size in Jomon and Yayoi females was not correlated with their general pelvic or body size, and there were correlations between sexually dimorphic aspects of true pelvis shape and either the false pelvis or body size in males but not females. CONCLUSIONS These results suggest that the obstetrical dimensions in small-bodied Jomon females were maintained for obstetric needs.
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Affiliation(s)
- Hirofumi Takamuku
- The Doigahama Site Anthropological Museum, Shimonoseki City, Yamaguchi, Japan
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20
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Grunstra NDS, Zachos FE, Herdina AN, Fischer B, Pavličev M, Mitteroecker P. Humans as inverted bats: A comparative approach to the obstetric conundrum. Am J Hum Biol 2019; 31:e23227. [PMID: 30810261 PMCID: PMC6492174 DOI: 10.1002/ajhb.23227] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 01/19/2023] Open
Abstract
OBJECTIVES The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. Here, we outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primates and other mammals. METHODS We combined a literature review with comparative analyses of neonatal and female body and brain mass, using three existing datasets. We also present images of bony pelves of a diverse sample of taxa. RESULTS Bats, certain non-human primates, seals, and most ungulates, including whales, have much larger relative neonatal masses than humans, and they all differ in their anatomical adaptations for childbirth. Bats, as a group, are particularly interesting in this context as they give birth to the relatively largest neonates, and their pelvis is highly dimorphic: Whereas males have a fused symphysis, a ligament bridges a large pubic gap in females. The resulting strong demands on the widened and vulnerable pelvic floor likely are relaxed by roosting head-down. CONCLUSIONS Parturition has constituted a strong selective force in many non-human placentals. We illustrated how the demands on pelvic morphology resulting from locomotion, pelvic floor stability, childbirth, and perhaps also erectile function in males have been traded off differently in mammals, depending on their locomotion and environment. Exploiting the power of a comparative approach, we present new hypotheses and research directions for resolving the obstetric conundrum in humans.
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Affiliation(s)
- Nicole D. S. Grunstra
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Mammal CollectionNatural History Museum ViennaViennaAustria
| | - Frank E. Zachos
- Mammal CollectionNatural History Museum ViennaViennaAustria
- Department of Integrative ZoologyUniversity of ViennaViennaAustria
| | | | - Barbara Fischer
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
| | - Mihaela Pavličev
- Cincinnati Children's Hospital Medical CenterCincinnatiOhio
- Department of PediatricsUniversity of Cincinnati College of MedicineCincinnatiOhio
- Department of PhilosophyUniversity of CincinnatiCincinnatiOhio
| | - Philipp Mitteroecker
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
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21
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Auerbach BM, King KA, Campbell RM, Campbell ML, Sylvester AD. Variation in obstetric dimensions of the human bony pelvis in relation to age‐at‐death and latitude. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2018; 167:628-643. [DOI: 10.1002/ajpa.23690] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 06/11/2018] [Accepted: 07/10/2018] [Indexed: 12/24/2022]
Affiliation(s)
- Benjamin M. Auerbach
- Department of Anthropology The University of Tennessee Knoxville Tennessee
- Department of Ecology and Evolutionary Biology The University of Tennessee Knoxville Tennessee
| | - Kathyrn A. King
- Department of Anthropology University of Arkansas at Little Rock Little Rock Arkansas
| | - Ryan M. Campbell
- Center for Archaeological Investigations Southern Illinois University Carbondale Illinois
| | - Meadow L. Campbell
- Basic Sciences, College of Chiropractic Medicine, Logan University Chesterfield Missouri
| | - Adam D. Sylvester
- Center for Functional Anatomy and Evolution Johns Hopkins University School of Medicine Baltimore Maryland
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22
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Betti L. Human Variation in Pelvic Shape and the Effects of Climate and Past Population History. Anat Rec (Hoboken) 2017; 300:687-697. [PMID: 28297180 DOI: 10.1002/ar.23542] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 08/30/2016] [Accepted: 10/20/2016] [Indexed: 12/13/2022]
Abstract
The human pelvis is often described as an evolutionary compromise (obstetrical dilemma) between the requirements of efficient bipedal locomotion and safe parturition of a highly encephalized neonate, that has led to a tight fit between the birth canal and the head and body of the foetus. Strong evolutionary constraints on the shape of the pelvis can be expected under this scenario. On the other hand, several studies have found a significant level of pelvic variation within and between human populations, a fact that seems to contradict such expectations. The advantages of a narrow pelvis for locomotion have recently been challenged, suggesting that the tight cephalo-pelvic fit might not stem from the hypothesized obstetrical dilemma. Moreover, the human pelvis appears to be under lower constraints and to have relatively higher evolvability than other closely related primates. These recent findings substantially change the way in which we interpret variation in the human pelvis, and help make sense of the high diversity in pelvic shape observed within and among modern populations. A lower magnitude of covariance between functionally important regions ensured that a wide range of morphological variation was available within populations, enabling natural selection to generate pelvic variation between populations living in different environments. Neutral processes such as genetic drift and differential migration also contributed to shaping modern pelvic diversity during and after the expansion of humans into and across the various continents. Anat Rec, 300:687-697, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Lia Betti
- Centre for Research in Evolutionary, Social and Inter-Disciplinary Anthropology, Department of Life Sciences, University of Roehampton, London, SW15 4JD, UK
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23
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Best KC, Garvin HM, Cabo LL. An Investigation into the Relationship between Human Cranial and Pelvic Sexual Dimorphism. J Forensic Sci 2017; 63:990-1000. [DOI: 10.1111/1556-4029.13669] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 09/18/2017] [Accepted: 09/19/2017] [Indexed: 11/29/2022]
Affiliation(s)
- Kaleigh C. Best
- Department of Anthropology; Southern Illinois University; 1000 Faner Drive Carbondale IL 62901
| | - Heather M. Garvin
- Department of Applied Forensic Sciences; Mercyhurst University; 501 E 38th Street Erie PA 16546
- Department of Anatomy; Des Moines University; 3200 Grand Avenue Des Moines IA 50312
| | - Luis L. Cabo
- Department of Applied Forensic Sciences; Mercyhurst University; 501 E 38th Street Erie PA 16546
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24
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Femoral neck-shaft angle and climate-induced body proportions. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:720-735. [DOI: 10.1002/ajpa.23311] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 08/23/2017] [Accepted: 08/29/2017] [Indexed: 01/25/2023]
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25
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Ubelaker DH, DeGaglia CM. Population variation in skeletal sexual dimorphism. Forensic Sci Int 2017; 278:407.e1-407.e7. [DOI: 10.1016/j.forsciint.2017.06.012] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 05/30/2017] [Accepted: 06/11/2017] [Indexed: 11/16/2022]
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Brůžek J, Santos F, Dutailly B, Murail P, Cunha E. Validation and reliability of the sex estimation of the human os coxae using freely available DSP2 software for bioarchaeology and forensic anthropology. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:440-449. [DOI: 10.1002/ajpa.23282] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/28/2017] [Accepted: 06/29/2017] [Indexed: 02/06/2023]
Affiliation(s)
- Jaroslav Brůžek
- Laboratoire PACEA - De la Préhistoire à l'Actuel: Culture; Environnement et Anthropologie, UMR 5199, CNRS, Université de Bordeaux, CS 50023; Pessac 33615 France
- Department of Anthropology and Human Genetics; Faculty of Science, Charles University; Prague 2 12000 Czech Republic
| | - Frédéric Santos
- Laboratoire PACEA - De la Préhistoire à l'Actuel: Culture; Environnement et Anthropologie, UMR 5199, CNRS, Université de Bordeaux, CS 50023; Pessac 33615 France
| | - Bruno Dutailly
- Laboratoire PACEA - De la Préhistoire à l'Actuel: Culture; Environnement et Anthropologie, UMR 5199, CNRS, Université de Bordeaux, CS 50023; Pessac 33615 France
| | - Pascal Murail
- Laboratoire PACEA - De la Préhistoire à l'Actuel: Culture; Environnement et Anthropologie, UMR 5199, CNRS, Université de Bordeaux, CS 50023; Pessac 33615 France
| | - Eugenia Cunha
- Centre for Functional Ecology; Laboratory of Forensic Anthropology, Life Sciences Department, University of Coimbra; Coimbra 3000-456 Portugal
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Mallard AM, Savell KRR, Auerbach BM. Morphological Integration of the Human Pelvis with Respect to Age and Sex. Anat Rec (Hoboken) 2017; 300:666-674. [DOI: 10.1002/ar.23547] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 08/01/2016] [Accepted: 10/13/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Angela M. Mallard
- Department of Anthropology; The University of Tennessee; Knoxville Tennessee 37996
| | - Kristen R. R. Savell
- Department of Anthropology; The University of Tennessee; Knoxville Tennessee 37996
| | - Benjamin M. Auerbach
- Department of Anthropology; The University of Tennessee; Knoxville Tennessee 37996
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28
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Candelas González N, Rascón Pérez J, Chamero B, Cambra-Moo O, González Martín A. Geometric morphometrics reveals restrictions on the shape of the female os coxae. J Anat 2016; 230:66-74. [PMID: 27485947 DOI: 10.1111/joa.12528] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2016] [Indexed: 12/19/2022] Open
Abstract
The methodology for sex determination in human skeletal remains depends on the different bone morphologies presented by men and women. Due to their direct implications in reproduction, the whole pelvis, particularly the os coxae, shows different characteristics in either sex. The sacrum and the os coxae constitute the birth canal. In this research study, the os coxae shape is analyzed using geometric morphometrics, providing information on morphology, regardless of size or any other factor beyond the geometry itself. A total of 46 adult ossa coxae from a Spanish archaeological collection were studied using geometric morphometrics. The results show that there is a restriction on the shape of female os coxae. In contrast, male os coxae presents a greater range of variation. The biological reason for this difference is the obstetrical dilemma; a concept defined as the anatomical conflict between bipedalism and the full-term birth of a neonate whose large head requires greater dimensions in the pelvic cavity. Our experimental data reinforce the validity of the obstetrical dilemma as source of the restriction on the shape of female ossa coxae. Additionally, according to the results obtained, size itself does not represent a condition for belonging to one sex or another.
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Affiliation(s)
- Nieves Candelas González
- Laboratorio de Poblaciones del Pasado (LAPP), Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Josefina Rascón Pérez
- Laboratorio de Poblaciones del Pasado (LAPP), Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | | | - Oscar Cambra-Moo
- Laboratorio de Poblaciones del Pasado (LAPP), Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Armando González Martín
- Laboratorio de Poblaciones del Pasado (LAPP), Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
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29
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Gruss LT, Schmitt D. The evolution of the human pelvis: changing adaptations to bipedalism, obstetrics and thermoregulation. Philos Trans R Soc Lond B Biol Sci 2016; 370:20140063. [PMID: 25602067 DOI: 10.1098/rstb.2014.0063] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The fossil record of the human pelvis reveals the selective priorities acting on hominin anatomy at different points in our evolutionary history, during which mechanical requirements for locomotion, childbirth and thermoregulation often conflicted. In our earliest upright ancestors, fundamental alterations of the pelvis compared with non-human primates facilitated bipedal walking. Further changes early in hominin evolution produced a platypelloid birth canal in a pelvis that was wide overall, with flaring ilia. This pelvic form was maintained over 3-4 Myr with only moderate changes in response to greater habitat diversity, changes in locomotor behaviour and increases in brain size. It was not until Homo sapiens evolved in Africa and the Middle East 200 000 years ago that the narrow anatomically modern pelvis with a more circular birth canal emerged. This major change appears to reflect selective pressures for further increases in neonatal brain size and for a narrow body shape associated with heat dissipation in warm environments. The advent of the modern birth canal, the shape and alignment of which require fetal rotation during birth, allowed the earliest members of our species to deal obstetrically with increases in encephalization while maintaining a narrow body to meet thermoregulatory demands and enhance locomotor performance.
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Affiliation(s)
| | - Daniel Schmitt
- Department of Evolutionary Anthropology, Duke University, Durham, NC, USA
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30
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Kurki HK, Decrausaz SL. Shape variation in the human pelvis and limb skeleton: Implications for obstetric adaptation. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 159:630-8. [PMID: 26699269 DOI: 10.1002/ajpa.22922] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/26/2015] [Accepted: 11/28/2015] [Indexed: 12/22/2022]
Abstract
OBJECTIVES Under the obstetrical dilemma (OD) hypothesis, selection acts on the human female pelvis to ensure a sufficiently sized obstetric canal for birthing a large-brained, broad shouldered neonate, while bipedal locomotion selects for a narrower and smaller pelvis. Despite this female-specific stabilizing selection, variability of linear dimensions of the pelvic canal and overall size are not reduced in females, suggesting shape may instead be variable among females of a population. Female canal shape has been shown to vary among populations, while male canal shape does not. Within this context, we examine within-population canal shape variation in comparison with that of noncanal aspects of the pelvis and the limbs. MATERIALS AND METHODS Nine skeletal samples (total female n = 101, male n = 117) representing diverse body sizes and shapes were included. Principal components analysis was applied to size-adjusted variables of each skeletal region. A multivariate variance was calculated using the weighted PC scores for all components in each model and F-ratios used to assess differences in within-population variances between sexes and skeletal regions. RESULTS Within both sexes, multivariate canal shape variance is significantly greater than noncanal pelvis and limb variances, while limb variance is greater than noncanal pelvis variance in some populations. Multivariate shape variation is not consistently different between the sexes in any of the skeletal regions. DISCUSSION Diverse selective pressures, including obstetrics, locomotion, load carrying, and others may act on canal shape, as well as genetic drift and plasticity, thus increasing variation in morphospace while protecting obstetric sufficiency.
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Affiliation(s)
- Helen K Kurki
- Department of Anthropology, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Sarah-Louise Decrausaz
- Division of Biological Anthropology, Department of Archaeology and Anthropology, University of Cambridge, Cambridge, CB2 3QG
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Brown KM. Selective pressures in the human bony pelvis: Decoupling sexual dimorphism in the anterior and posterior spaces. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2015; 157:428-40. [PMID: 25752812 DOI: 10.1002/ajpa.22734] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 02/15/2015] [Accepted: 02/16/2015] [Indexed: 12/17/2022]
Abstract
OBJECTIVES Sexual dimorphism in the human bony pelvis is commonly assumed to be related to the intensity of obstetrical selective pressures. With intense obstetrical selective pressures, there should be greater shape dimorphism; with minimal obstetrical selective pressures, there should be reduced shape dimorphism. This pattern is seen in the nondimorphic anterior spaces and highly dimorphic posterior spaces. Decoupling sexual dimorphism in these spaces may in turn be related to the differential influence of other selective pressures, such as biomechanical ones. MATERIALS AND METHODS The relationship between sexual dimorphism and selective pressures in the human pelvis was examined using five skeletal samples (total female n = 101; male n = 103). Pelvic shape was quantified by collecting landmark coordinate data on articulated pelves. Euclidean distance matrix analysis was used to extract the distances that defined the anterior and posterior pelvic spaces. Sex and body mass were used as proxies for obstetrical and biomechanical selective pressures, respectively. RESULTS MANCOVA analyses demonstrate significant effects of sex and body mass on distances in both the anterior and the posterior spaces. A comparison of the relative contribution of shape variance attributed to each of these factors suggests that the posterior space is more influenced by sex, and obstetrics by proxy, whereas the anterior space is more influenced by body mass, and biomechanics by proxy. CONCLUSIONS Although the overall shape of the pelvis has been influenced by obstetrical and biomechanical selective pressures, there is a differential response within the pelvis to these factors. These results provide new insight into the ongoing debate on the obstetrical dilemma hypothesis.
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Affiliation(s)
- Kirsten M Brown
- Department of Anatomy and Regenerative Biology, George Washington University School of Medicine and Health Sciences, Washington, DC, 20037
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How many specimens do I need? Sampling error in geometric morphometrics: testing the sensitivity of means and variances in simple randomized selection experiments. ZOOMORPHOLOGY 2015. [DOI: 10.1007/s00435-015-0253-z] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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