1
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Aulds M. Prevalence of sacroiliac joint fusion in females and males depending on parity status. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2024; 184:e24951. [PMID: 38783687 DOI: 10.1002/ajpa.24951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 04/14/2024] [Accepted: 04/24/2024] [Indexed: 05/25/2024]
Abstract
OBJECTIVES Previous research shows that sacroiliac (SI) joint fusion is age and sex dependent. Older individuals-specifically starting in the fifth or sixth decade of life-are more likely to develop SI fusion. Females have a lower frequency of SI joint fusion than males, perhaps due to pregnancy or parturition. This study examines the relationship between SI joint fusion with both sex and parity status in females. The issue is whether the prevalence of SI fusion in nulliparous females is more similar to that of males or parous females. MATERIALS AND METHODS The sample consists of 46 nulliparous females, 119 parous females, and 158 males from the William M. Bass Donated Skeletal Collection. Ages of the individuals ranged from 50 to 89 years. Sex, age, and parity status were self-reported. RESULTS The frequency of SI joint fusion is significantly different among males (13.29%), nulliparous females (6.52%), and parous females (0.84%). Pairwise comparison of the three groups for SI joint fusion shows that parous females and males are significantly different, but nulliparous females are nonsignificantly different from parous females and males. DISCUSSION Parity status does not appear to be a factor in the sexually dimorphic nature of SI joint fusion in this sample. Rather, biomechanical and hormonal factors may have a greater contribution to higher rates of SI joint fusion in males than females.
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Affiliation(s)
- Meredith Aulds
- Department of Geography and Anthropology, Louisiana State University, Baton Rouge, Louisiana, USA
- Department of Anthropology, Purdue University, West Lafayette, Indiana, USA
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2
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Rmoutilová R, Brůžek J, Gómez-Olivencia A, Madelaine S, Couture-Veschambre C, Holliday T, Maureille B. Sex estimation of the adult Neandertal Regourdou 1 (Montignac, France): Implications for sexing human fossil remains. J Hum Evol 2024; 189:103470. [PMID: 38552260 DOI: 10.1016/j.jhevol.2023.103470] [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: 12/05/2022] [Revised: 11/17/2023] [Accepted: 11/17/2023] [Indexed: 04/08/2024]
Abstract
Sex is a biological trait fundamental to the study of hominin fossils. Among the many questions that can be addressed are those related to taxonomy, biological variability, sexual dimorphism, paleoobstetrics, funerary selection, and paleodemography. While new methodologies such as paleogenomics or paleoproteomics can be used to determine sex, they have not been systematically applied to Pleistocene human remains due to their destructive nature. Therefore, we estimated sex from the coxal bone of the newly discovered pelvic remains of the Regourdou 1 Neandertal (Southwest France, MIS 5) based on morphological and metric data employing two methods that have been recently revised and shown to be reliable in multiple studies. Both methods calculate posterior probabilities of the estimate. The right coxal bone of Regourdou 1 was partially reconstructed providing additional traits for sex estimation. These methods were cross validated on 14 sufficiently preserved coxal bones of specimens from the Neandertal lineage. Our results show that the Regourdou 1 individual, whose postcranial skeleton is not robust, is a male, and that previous sex attributions of comparative Neandertal specimens are largely in agreement with those obtained here. Our results encourage additional morphological research of fossil hominins in order to develop a set of methods that are applicable, reliable, and reproducible.
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Affiliation(s)
- Rebeka Rmoutilová
- Department of Anthropology and Human Genetics, Faculty of Science, Charles University, Viničná 7, 128 00, Prague, Czech Republic; University of Bordeaux, CNRS, MC, PACEA, UMR 5199, F-33600, Pessac, France; Hrdlicka Museum of Man, Faculty of Science, Charles University, Viničná 7, 128 00 Prague 2, Czech Republic.
| | - Jaroslav Brůžek
- Department of Anthropology and Human Genetics, Faculty of Science, Charles University, Viničná 7, 128 00, Prague, Czech Republic; University of Bordeaux, CNRS, MC, PACEA, UMR 5199, F-33600, Pessac, France
| | - Asier Gómez-Olivencia
- Departamento de Geología, Facultad de Ciencia y Tecnología, Universidad Del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Leioa, Spain; Sociedad de Ciencias Aranzadi, Donostia-San Sebastián, Spain; Centro UCM-ISCIII de Investigacion Sobre Evolución y Comportamiento Humanos, Madrid, Spain
| | - Stéphane Madelaine
- University of Bordeaux, CNRS, MC, PACEA, UMR 5199, F-33600, Pessac, France; Musée National de Préhistoire, 1 Rue Du Musée, 24620, Les Eyzies-de-Tayac Sireuil, France
| | | | - Trenton Holliday
- Tulane University, Department of Anthropology, 101 Dinwiddie Hall, New Orleans, LA, 70118, USA; Centre for the Exploration of the Deep Human Journey, University of the Witwatersrand, Private Bag 3, Wits, 2050, RSA, South Africa
| | - Bruno Maureille
- University of Bordeaux, CNRS, MC, PACEA, UMR 5199, F-33600, Pessac, France
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3
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Mitteroecker P, Fischer B. Evolution of the human birth canal. Am J Obstet Gynecol 2024; 230:S841-S855. [PMID: 38462258 DOI: 10.1016/j.ajog.2022.09.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 09/07/2022] [Accepted: 09/07/2022] [Indexed: 03/12/2024]
Abstract
It seems puzzling why humans have evolved such a small and rigid birth canal that entails a relatively complex process of labor compared with the birth canal of our closest relatives, the great apes. This study reviewed insights into the evolution of the human birth canal from recent theoretical and empirical studies and discussed connections to obstetrics, gynecology, and orthopedics. Originating from the evolution of bipedality and the large human brain million years ago, the evolution of the human birth canal has been characterized by complex trade-off dynamics among multiple biological, environmental, and sociocultural factors. The long-held notion that a wider pelvis has not evolved because it would be disadvantageous for bipedal locomotion has not yet been empirically verified. However, recent clinical and biomechanical studies suggest that a larger birth canal would compromise pelvic floor stability and increase the risk of incontinence and pelvic organ prolapse. Several mammals have neonates that are equally large or even larger than human neonates compared to the size of the maternal birth canal. In these species, the pubic symphysis opens widely to allow successful delivery. Biomechanical and developmental constraints imposed by bipedality have hindered this evolutionary solution in humans and led to the comparatively rigid pelvic girdle in pregnant women. Mathematical models have shown why the evolutionary compromise to these antagonistic selective factors inevitably involves a certain rate of fetopelvic disproportion. In addition, these models predict that cesarean deliveries have disrupted the evolutionary equilibrium and led to new and ongoing evolutionary changes. Different forms of assisted birth have existed since the stone age and have become an integral part of human reproduction. Paradoxically, by buffering selection, they may also have hindered the evolution of a larger birth canal. Many of the biological, environmental, and sociocultural factors that have influenced the evolution of the human birth canal vary globally and are subject to ongoing transitions. These differences may have contributed to the global variation in the form of the birth canal and the difficulty of labor, and they likely continue to change human reproductive anatomy.
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Affiliation(s)
- Philipp Mitteroecker
- Unit for Theoretical Biology, Department of Evolutionary Biology, University of Vienna, Vienna, Austria.
| | - Barbara Fischer
- Unit for Theoretical Biology, Department of Evolutionary Biology, University of Vienna, Vienna, Austria
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4
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Gómez-Robles A, Nicolaou C, Smaers JB, Sherwood CC. The evolution of human altriciality and brain development in comparative context. Nat Ecol Evol 2024; 8:133-146. [PMID: 38049480 PMCID: PMC10781642 DOI: 10.1038/s41559-023-02253-z] [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: 03/02/2023] [Accepted: 10/18/2023] [Indexed: 12/06/2023]
Abstract
Human newborns are considered altricial compared with other primates because they are relatively underdeveloped at birth. However, in a broader comparative context, other mammals are more altricial than humans. It has been proposed that altricial development evolved secondarily in humans due to obstetrical or metabolic constraints, and in association with increased brain plasticity. To explore this association, we used comparative data from 140 placental mammals to measure how altriciality evolved in humans and other species. We also estimated how changes in brain size and gestation length influenced the timing of neurodevelopment during hominin evolution. Based on our data, humans show the highest evolutionary rate to become more altricial (measured as the proportion of adult brain size at birth) across all placental mammals, but this results primarily from the pronounced postnatal enlargement of brain size rather than neonatal changes. In addition, we show that only a small number of neurodevelopmental events were shifted to the postnatal period during hominin evolution, and that they were primarily related to the myelination of certain brain pathways. These results indicate that the perception of human altriciality is mostly driven by postnatal changes, and they point to a possible association between the timing of myelination and human neuroplasticity.
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Affiliation(s)
- Aida Gómez-Robles
- Department of Anthropology, University College London, London, UK.
- Department of Genetics, Evolution and Environment, University College London, London, UK.
| | | | - Jeroen B Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, NY, USA
| | - Chet C Sherwood
- Center for the Advanced Study of Human Paleobiology, Department of Anthropology, The George Washington University, Washington, DC, USA
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5
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Macionis V. Fetal head-down posture may explain the rapid brain evolution in humans and other primates: An interpretative review. Brain Res 2023; 1820:148558. [PMID: 37634686 DOI: 10.1016/j.brainres.2023.148558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 08/22/2023] [Accepted: 08/24/2023] [Indexed: 08/29/2023]
Abstract
Evolutionary cerebrovascular consequences of upside-down postural verticality of the anthropoid fetus have been largely overlooked in the literature. This working hypothesis-based report provides a literature interpretation from an aspect that the rapid evolution of the human brain has been promoted by fetal head-down position due to maternal upright and semi-upright posture. Habitual vertical torso posture is a feature not only of humans, but also of monkeys and non-human apes that spend considerable time in a sitting position. Consequently, the head-down position of the fetus may have caused physiological craniovascular hypertension that stimulated expansion of the intracranial vessels and acted as an epigenetic physiological stress, which enhanced neurogenesis and eventually, along with other selective pressures, led to the progressive growth of the anthropoid brain and its organization. This article collaterally opens a new insight into the conundrum of high cephalopelvic proportions (i.e., the tight fit between the pelvic birth canal and fetal head) in phylogenetically distant lineages of monkeys, lesser apes, and humans. Low cephalopelvic proportions in non-human great apes could be accounted for by their energetically efficient horizontal nest-sleeping and consequently by their larger body mass compared to monkeys and lesser apes that sleep upright. One can further hypothesize that brain size varies in anthropoids according to the degree of exposure of the fetus to postural verticality. The supporting evidence for this postulation includes a finding that in fossil hominins cerebral blood flow rate increased faster than brain volume. This testable hypothesis opens a perspective for research on fetal postural cerebral hemodynamics.
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6
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Nakamichi M. Non-human primate birth and human birth. Primates 2023; 64:551-556. [PMID: 37843662 DOI: 10.1007/s10329-023-01097-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 09/29/2023] [Indexed: 10/17/2023]
Affiliation(s)
- Masayuki Nakamichi
- Graduate School of Human Sciences, Osaka University, Suita, 565-0871, Japan.
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7
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Cordey C, Webb NM, Haeusler M. Take it to the limit: The limitations of energetic explanations for birth timing in humans. Evol Med Public Health 2023; 11:415-428. [PMID: 38022799 PMCID: PMC10644907 DOI: 10.1093/emph/eoad035] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 10/18/2023] [Indexed: 12/01/2023] Open
Abstract
A hallmark of modern humans is that our newborns are neurologically immature compared to other primates. It is disputed whether this so-called secondary altriciality evolved due to remodelling of the pelvis associated with bipedal locomotion, as suggested by the obstetrical dilemma hypothesis, or from maternal energetic limitations during pregnancy. Specifically, the 'Energetics of Gestation and Growth' (EGG) hypothesis posits that birth is initiated when foetal energy requirements exceed the maximum sustained maternal metabolic rate during pregnancy at around 2.1 × basal metabolic rate (BMR) of the non-pregnant, non-lactating condition (NPNL). However, the metabolic threshold argued under the EGG framework is derived from one study with a small sample size of only 12 women from the UK. Accordingly, we performed a meta-analysis of all published studies on metabolic scopes during pregnancy to better account for variability. After excluding 3 studies with methodological issues, a total of 12 studies with 303 women from 5 high- and 3 low-income countries were analysed. On average, pregnancy was found to be less metabolically challenging than previously suggested. The studies revealed substantial variation in metabolic scope during pregnancy, which was not reflected by variation in birth timing. Further, in a third of the studies, the metabolic rates exceeded 2.1 × BMRNPNL. Our simulation of foetal energy requirements demonstrated that this metabolic threshold of 2.1 × BMRNPNL cannot realistically be crossed by the foetus around the time of birth. These findings imply that metabolic constraints are not the main limiting factor dictating gestation length.
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Affiliation(s)
- Cédric Cordey
- Institute of Evolutionary Medicine, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
| | - Nicole M Webb
- Institute of Evolutionary Medicine, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
- Department of Palaeoanthropology, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, 60325, Frankfurt am Main, Germany
| | - Martin Haeusler
- Institute of Evolutionary Medicine, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
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8
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Warrener A. The multifactor pelvis: An alternative to the adaptationist approach of the obstetrical dilemma. Evol Anthropol 2023; 32:260-274. [PMID: 37527355 DOI: 10.1002/evan.21997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 02/23/2023] [Accepted: 07/08/2023] [Indexed: 08/03/2023]
Abstract
The obstetrical dilemma describes the competing demands that a bipedally adapted pelvis and a large-brained neonate place on human childbirth and is the predominant model within which hypotheses about the evolution of the pelvis are framed. I argue the obstetrical dilemma follows the adaptationist program outlined by Gould and Lewontin in 1979 and should be replaced with a new model, the multifactor pelvis. This change will allow thorough consideration of nonadaptive explanations for the evolution of the human pelvis and avoid negative social impacts from considering human childbirth inherently dangerous. First, the atomization of the pelvis into discrete traits is discussed, after which current evidence for both adaptive and nonadaptive hypotheses is evaluated, including childbirth, locomotion, shared genetics with other traits under selection, evolutionary history, genetic drift, and environmental and epigenetic influences on the pelvis.
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Affiliation(s)
- Anna Warrener
- Department of Anthropology, University of Colorado Denver, Denver, Colorado, USA
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9
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Pollen AA, Kilik U, Lowe CB, Camp JG. Human-specific genetics: new tools to explore the molecular and cellular basis of human evolution. Nat Rev Genet 2023; 24:687-711. [PMID: 36737647 PMCID: PMC9897628 DOI: 10.1038/s41576-022-00568-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2022] [Indexed: 02/05/2023]
Abstract
Our ancestors acquired morphological, cognitive and metabolic modifications that enabled humans to colonize diverse habitats, develop extraordinary technologies and reshape the biosphere. Understanding the genetic, developmental and molecular bases for these changes will provide insights into how we became human. Connecting human-specific genetic changes to species differences has been challenging owing to an abundance of low-effect size genetic changes, limited descriptions of phenotypic differences across development at the level of cell types and lack of experimental models. Emerging approaches for single-cell sequencing, genetic manipulation and stem cell culture now support descriptive and functional studies in defined cell types with a human or ape genetic background. In this Review, we describe how the sequencing of genomes from modern and archaic hominins, great apes and other primates is revealing human-specific genetic changes and how new molecular and cellular approaches - including cell atlases and organoids - are enabling exploration of the candidate causal factors that underlie human-specific traits.
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Affiliation(s)
- Alex A Pollen
- Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, USA.
- Department of Neurology, University of California, San Francisco, San Francisco, CA, USA.
| | - Umut Kilik
- Institute of Human Biology (IHB), Roche Pharma Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Craig B Lowe
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA.
| | - J Gray Camp
- Institute of Human Biology (IHB), Roche Pharma Research and Early Development, Roche Innovation Center Basel, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
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10
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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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11
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Morimoto N, Kawada M, Tomizawa Y, Kaneko A, Nishimura T. Pelvic shape change in adult Japanese macaques and implications for childbirth at old age. Proc Natl Acad Sci U S A 2023; 120:e2300714120. [PMID: 37459534 PMCID: PMC10372569 DOI: 10.1073/pnas.2300714120] [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: 01/15/2023] [Accepted: 06/07/2023] [Indexed: 07/20/2023] Open
Abstract
Pelvic morphology exhibits a particular sexual dimorphism in humans, which reflects obstetrical constraints due to the tight fit between neonates and mothers. Huseynov et al. [Proc. Natl. Acad. Sci. U.S.A. 113, 5227-5232 (2016)] showed that in humans, pelvic sexual dimorphism is greatest around the age of highest fertility, and it becomes less marked in association with menopause in females. They proposed that this reflects changes of obstetrical versus locomotor functional demands in females. It remains unknown whether such developmental adjustment of the pelvic morphology is unique to humans. Macaques exhibit human-like cephalopelvic proportions, but they lack menopause and usually maintain fertility throughout adulthood. Here, we track pelvic development in Japanese macaques from neonate to advanced ages using computed tomography-based data. We show that female pelvic morphology changes throughout adult life, reaching the obstetrically most favorable shape at advanced ages rather than around primiparity. We hypothesize that pelvic morphology in Japanese macaques is developmentally adjusted to childbirth at advanced ages, where obstetrical risks are potentially higher than at younger ages. Our data contribute to the growing evidence that the female primate pelvis changes its morphology during the whole lifespan, possibly adjusting for changing functional demands during adulthood.
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Affiliation(s)
- Naoki Morimoto
- Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, 606-8502Kyoto, Japan
| | - Mikaze Kawada
- Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, 606-8502Kyoto, Japan
| | - Yuma Tomizawa
- Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, 606-8502Kyoto, Japan
| | - Akihisa Kaneko
- Center for the Evolutionary Origins of Human Behavior, Kyoto University, 484-8506Inuyama, Japan
| | - Takeshi Nishimura
- Center for the Evolutionary Origins of Human Behavior, Kyoto University, 484-8506Inuyama, Japan
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12
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Abstract
We propose a dynamic production function of population health and mortality from birth onward. Our parsimonious model provides an excellent fit for the mortality and survival curves for primate and human populations since 1816. The model sheds light on the dynamics behind many phenomena documented in the literature. Simple extensions of the model can reproduce (1) the existence and evolution of mortality gradients across socioeconomic statuses documented in the literature, (2) nonmonotonic dynamic effects of in utero shocks, (3) persistent or scarring effects of wars, and (4) mortality displacement after large temporary shocks, such as extreme weather.
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Affiliation(s)
- Adriana Lleras-Muney
- Department of Economics, University of California, Los Angeles, Los Angeles, CA, USA
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13
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Sulikowska-Drozd A, Maltz TK, Janiszewska K. Flexible embryonic shell allies large offspring size and anti-predatory protection in viviparous snails. Sci Rep 2022; 12:17881. [PMID: 36289315 PMCID: PMC9605993 DOI: 10.1038/s41598-022-22651-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 10/18/2022] [Indexed: 01/20/2023] Open
Abstract
The evolutionary conflicts between viviparous reproductive mode and skeleton shape may occur whenever the space available for embryo development or delivery is limited by hard inflexible structures of a parent (bones, shell, etc.). In tetrapods, offspring size is at odds with female locomotion efficiency, which results in obstetric selection. We suggest a similar relationship for viviparous gastropods, where spacious canal needed for embryo delivery may interfere with anti-predatory role of narrow and toothed shell aperture. We explored this hypothesis in the group of viviparous land snails (Clausiliidae, subfamily Phaedusinae), known for complex apertural barriers protecting the shell interior. Most of the shell structure modifications we recorded facilitate the delivery of embryos but simultaneously reduce the safeguard of a narrow shell opening. However, we also observed highly flexible embryonic shells that may withstand squeezing between apertural barriers during birth. We investigated the microstructure of these flexible embryonic shells, compared to the typical hard shells of clausiliid embryos, which are rigid and unpliable already in the genital tract of the parent. Our results suggest that the unusual flexibility, which is related to a low number of organomineral layers in the shell, evolved in two phylogenetically distant lineages of Phaedusinae. This adaptation reduces mechanical constraints for birth of the neonates but allows to maintain the protective function of the apertural barriers.
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Affiliation(s)
- A. Sulikowska-Drozd
- grid.10789.370000 0000 9730 2769Department of Invertebrate Zoology and Hydrobiology, University of Lodz, Lodz, Poland
| | - T. K. Maltz
- grid.8505.80000 0001 1010 5103Museum of Natural History, University of Wrocław, Wrocław, Poland
| | - K. Janiszewska
- grid.413454.30000 0001 1958 0162Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland
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14
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Young M, Richard D, Grabowski M, Auerbach BM, de Bakker BS, Hagoort J, Muthuirulan P, Kharkar V, Kurki HK, Betti L, Birkenstock L, Lewton KL, Capellini TD. The developmental impacts of natural selection on human pelvic morphology. SCIENCE ADVANCES 2022; 8:eabq4884. [PMID: 35977020 PMCID: PMC9385149 DOI: 10.1126/sciadv.abq4884] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 06/29/2022] [Indexed: 06/15/2023]
Abstract
Evolutionary responses to selection for bipedalism and childbirth have shaped the human pelvis, a structure that differs substantially from that in apes. Morphology related to these factors is present by birth, yet the developmental-genetic mechanisms governing pelvic shape remain largely unknown. Here, we pinpoint and characterize a key gestational window when human-specific pelvic morphology becomes recognizable, as the ilium and the entire pelvis acquire traits essential for human walking and birth. We next use functional genomics to molecularly characterize chondrocytes from different pelvic subelements during this window to reveal their developmental-genetic architectures. We then find notable evidence of ancient selection and genetic constraint on regulatory sequences involved in ilium expansion and growth, findings complemented by our phenotypic analyses showing that variation in iliac traits is reduced in humans compared to African apes. Our datasets provide important resources for musculoskeletal biology and begin to elucidate developmental mechanisms that shape human-specific morphology.
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Affiliation(s)
- Mariel Young
- Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Daniel Richard
- Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Mark Grabowski
- Research Centre in Evolutionary Anthropology and Palaeoecology, Liverpool John Moores University, Liverpool L3 3AF, UK
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway
| | - Benjamin M. Auerbach
- Department of Anthropology, The University of Tennessee, Knoxville, TN, USA
- Department of Ecology and Evolutionary Biology, The University of Tennessee, Knoxville, TN, USA
| | - Bernadette S. de Bakker
- Department of Obstetrics and Gynecology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, Netherlands
- Amsterdam Reproduction and Development Research Institute, Amsterdam, Netherlands
| | - Jaco Hagoort
- Department of Medical Biology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, Netherlands
| | | | - Vismaya Kharkar
- Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Helen K. Kurki
- Department of Anthropology, University of Victoria, STN CSC, Victoria, BC V8W 2Y2, Canada
| | - Lia Betti
- School of Life and Health Sciences, University of Roehampton, London SW15 4JD, UK
| | | | - Kristi L. Lewton
- Department of Integrative Anatomical Sciences, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Terence D. Capellini
- Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Broad Institute of MIT and Harvard, Cambridge, MA, USA
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15
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de La Salles AYF, de Andrade JK, de Souza JG, Freitas KDB, Carreiro ADN, Veloso EVL, Rocha EF, Klem MAP, Mendonça FTM, de Menezes DJA. Anatomy applied to image diagnosis of the hind limb in the black-striped capuchin (Sapajus libidinosus Spix, 1823). Am J Primatol 2022; 84:e23416. [PMID: 35848101 DOI: 10.1002/ajp.23416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/27/2022] [Accepted: 06/15/2022] [Indexed: 11/09/2022]
Abstract
The knowledge of anatomy and imaging exams emerges as an important tool in the study of evolutionary processes of a species, in the elaboration of diagnosis, and the successful choice of the appropriate clinical and surgical procedures. Therefore, this study aims to describe the osteology of the hind limb of Sapajus libidinosus by means of gross, radiographic, and tomographic images. Four cadavers were used in the macroscopic analysis and five animals for the imaging exams, of which four were eventually euthanized and added to the macroscopic study. For imaging exams, they were kept anesthetized. All bones of the hind limb were documented, their structures were described, and compared with data in the literature from human and nonhuman primates. We have performed Student's t test for independent samples. There was no statistical difference between the sexes regarding the length of the hind limb bones. The coxal bone was largely well described using imaging methods. A small penile bone was present at the tip of the penis and it could be identified by all analysis methods. The femur, as well as the tibia and fibula, were not well portrayed in their proximal and distal epiphyses by radiography (Rx). However, they were well identified on tomography. No third trochanter was observed in the femur and the patella had a triangular shape. All the structures described by gross anatomy of the tarsus and metatarsus could be identified by Rx and tomography. More subtle structures, such as the popliteal notch on the tibia, and the gluteal tuberosity pectineal line and facies aspera on the coxal bone, were not identified by medical imaging. S. libidinosus presented anatomical characteristics that were similar to those of larger New World and Old World monkeys, including man. This suggests it's value as an experimental model for studies in recent primates.
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Affiliation(s)
- Ana Y F de La Salles
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil
| | | | - Joyce G de Souza
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil
| | - Kelvis de B Freitas
- Postgraduate Program in Structural and Functional Biology, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil
| | - Artur da N Carreiro
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil
| | - Edson V L Veloso
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil
| | - Ediane F Rocha
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil
| | - Marcius A P Klem
- Institute of Veterinary Radiology, Natal, Rio Grande do Norte, Brazil
| | - Fábio T M Mendonça
- Veterinary Health Center, Universidade Potiguar, Natal, Rio Grande do Norte, Brazil
| | - Danilo J A de Menezes
- Postgraduate Program in Animal Science and Health, Center for Rural Health and Technology, Federal University of Campina Grande, Patos, Paraíba, Brazil.,Department of Morphology, Federal University of Rio Grande do Norte, Natal, Rio Grande do Norte, Brazil
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16
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do Amaral LQ. Safe Carrying of Heavy Infants Together With Hair Properties Explain Human Evolution. Front Psychol 2022; 13:854948. [PMID: 35712208 PMCID: PMC9197501 DOI: 10.3389/fpsyg.2022.854948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/07/2022] [Indexed: 11/13/2022] Open
Abstract
As a physicist, my scientific career was interrupted by maternity, and afterward retaken, with a parallel independent personal perspective on human evolution. My previous published contributions are reanalyzed as Hypothesis and Theory. The focus is on safe infant carrying in primates, sexual selection among Hominoidea, fur reduction in hominins, and tensile properties of hominoid hairs, justifying the necessary change to bipedal locomotion from the overwhelming selective pressure of infant survival. The Discussion starts with analysis of existing bias against acceptance of these new ideas, first with rational arguments on bias existing between Exact Sciences and Biological Sciences. A reanalysis of data on elasticity of hominoid hairs is made, based on published differences between statistical analysis of measurements in exact and inexact sciences. A table constructed from the original data on hair elasticity allows a simplified discussion, based on statistics used in Physics in the study of “known samples,” adding extra information to the available data. Published data on hair density in primates and mammals allow the conclusion that hair elastic properties might have evolved correlated to the pressure of safe carrying of heavy infants, with an upper limit of 1 kgf/cm2 for safe infant clinging to primate mother’s hair. The Discussion enters then on the main ideological bias, related to the resistance in the academy to the idea that bipedalism could be connected to a “female problem,” that means, that it was not a “male acquisition.” Tripedal walk, occurring naturally among African Apes carrying their newborns, unable to support themselves by ventral clinging, is the natural candidate leading to evolution of bipedal locomotion. Tripedal walk as an intermediate stage to bipedalism was in fact theoretically proposed, but ignoring its role in primate transportation by ape mothers. The Discussion proceeds to a proposal of phylogenetic evolution of Hominoids, the usual focus on the males changes to the role of females with infants, allowing an integrated view on Hominin evolution, with fur reduction and thermoregulation of the naked skin, with subcutaneous insulating fat layer. The model for earliest hominin social structures is based on huddle formation and hormonally defined rites of passage.
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17
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Lassek WD, Gaulin SJC. Substantial but Misunderstood Human Sexual Dimorphism Results Mainly From Sexual Selection on Males and Natural Selection on Females. Front Psychol 2022; 13:859931. [PMID: 35664212 PMCID: PMC9156798 DOI: 10.3389/fpsyg.2022.859931] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 03/28/2022] [Indexed: 01/05/2023] Open
Abstract
Human sexual dimorphism has been widely misunderstood. A large literature has underestimated the effect of differences in body composition and the role of male contest competition for mates. It is often assumed that sexually dimorphic traits reflect a history of sexual selection, but natural selection frequently builds different phenotypes in males and females. The relatively small sex difference in stature (∼7%) and its decrease during human evolution have been widely presumed to indicate decreased male contest competition for mates. However, females likely increased in stature relative to males in order to successfully deliver large-brained neonates through a bipedally-adapted pelvis. Despite the relatively small differences in stature and body mass (∼16%), there are marked sex differences in body composition. Across multiple samples from groups with different nutrition, males typically have 36% more lean body mass, 65% more muscle mass, and 72% more arm muscle than women, yielding parallel sex differences in strength. These sex differences in muscle and strength are comparable to those seen in primates where sexual selection, arising from aggressive male mating competition, has produced high levels of dimorphism. Body fat percentage shows a reverse pattern, with females having ∼1.6 times more than males and depositing that fat in different body regions than males. We argue that these sex differences in adipose arise mainly from natural selection on women to accumulate neurodevelopmental resources.
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Affiliation(s)
| | - Steven J. C. Gaulin
- Department of Anthropology, University of California, Santa Barbara, Santa Barbara, CA, United States
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18
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Gorman J, Roberts CA, Newsham S, Bentley GR. Squatting, pelvic morphology and a reconsideration of childbirth difficulties. Evol Med Public Health 2022; 10:243-255. [PMID: 35663511 PMCID: PMC9154243 DOI: 10.1093/emph/eoac017] [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: 08/16/2021] [Accepted: 04/19/2022] [Indexed: 11/14/2022] Open
Abstract
Childbirth is commonly viewed as difficult in human females, encompassed by the 'Obstetrical Dilemma' (OD) described by early palaeoanthropologists as an evolved trade-off between a narrow pelvis necessitated by bipedalism and a large-brained fetal head. The OD has been challenged on several grounds. We add to these challenges by suggesting humans likely squatted regularly during routine tasks prior to the advent of farming societies and use of seats. We suggest that habitual squatting, together with taller stature and better nutrition of ancestral hunter-gatherers compared with later Neolithic and industrial counterparts, obviated an OD. Instead, difficulties with parturition may have arisen much later in our history, accompanying permanent settlements, poorer nutrition, greater infectious disease loads and negligible squatting in daily life. We discuss bioarchaeological and contemporary data that support these viewpoints, suggest ways in which this hypothesis might be tested further and consider its implications for obstetrical practice. Lay Summary Human childbirth is viewed as universally difficult. Evidence from physical therapies/engineering and studies of living and ancestral humans illustrates habitual squatting widens the pelvis and could improve childbirth outcomes. Obstetrical difficulties emerged late in prehistory accompanying settled agriculture, poorer nutrition and less squatting. Specific physical exercises could improve obstetrical practice.
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Affiliation(s)
- John Gorman
- Independent Scholar, Greenhead, Brampton, Northumberland CA8 7HX, UK
| | - Charlotte A Roberts
- Department of Archaeology, Durham University, Dawson Building, South Road, Durham DH1 3LE, UK
| | - Sally Newsham
- Department of Gynaecology, North Cumbria Integrated Care NHS Foundation Trust, Cumbria CA2 7HY, UK
| | - Gillian R Bentley
- Department of Anthropology, Durham University, Dawson Building, South Road, Durham DH1 3LE, UK
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19
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Abstract
SignificanceDuring human birth, the risk of complications is relatively high because of the comparatively large dimensions of the fetal head and shoulders relative to the maternal birth canal. Here we show that humans exhibit a developmental mode of the shoulders that likely contributes to mitigating obstetrical problems. Human shoulder growth is decelerated before birth but accelerated after birth, which stands in contrast to the more uniform shoulder growth trajectories of chimpanzees and macaques. This indicates that fetal developmental modifications were required during human evolution not only in the head but also in the shoulders to compensate obstetrical constraints.
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20
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Childbirth and Infant Care in Early Human Ancestors: What the Bones Tell Us. EVOLUTIONARY PSYCHOLOGY 2022. [DOI: 10.1007/978-3-030-76000-7_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
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21
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Abstract
Humans have a prolonged childhood, which begins with an immature developmental state at birth. We take care of these helpless infants through a variety of cultural adaptations, including material culture, provisioning of food, and shared child care. Our species has long been characterized as having secondary altriciality, but an examination of human life history shows that we are fundamentally precocial, despite seeming helpless at birth. Human babies are also relatively large and overall require substantial attention and energy from caregivers. Previous work has focused on how culture permits us to give birth to helpless young and how our cultural adaptation solves problems stemming from encephalization. The birth of these dependent, costly creatures poses challenges but also creates opportunities by enhancing the development of social and emotional relationships with caregivers as well as language acquisition and enculturation.
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Affiliation(s)
- Karen R. Rosenberg
- Department of Anthropology, University of Delaware, Newark, Delaware 19716, USA
- Philosophical Faculty, University of Hradec Králové, 500 03 Hradec Králové, Czech Republic
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22
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Stansfield E, Fischer B, Grunstra NDS, Pouca MV, Mitteroecker P. The evolution of pelvic canal shape and rotational birth in humans. BMC Biol 2021; 19:224. [PMID: 34635119 PMCID: PMC8507337 DOI: 10.1186/s12915-021-01150-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 09/09/2021] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape. RESULTS Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. CONCLUSIONS This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.
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Affiliation(s)
- Ekaterina Stansfield
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
| | - Barbara Fischer
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria
| | - Nicole D S Grunstra
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria
- Konrad Lorenz Institute for Evolution and Cognition Research, Martinstrasse 12, 3400, Klosterneuburg, Austria
- Mammal Collection, Natural History Museum Vienna, Burgring 7, 1010, Vienna, Austria
| | - Maria Villa Pouca
- Faculty of Engineering of University of Porto (FEUP), Rua Dr. Roberto Frias, s/n, 4200-465, Porto, Portugal
- Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI/LAETA), Rua Dr. Roberto Frias, 400, 4200-465, Porto, Portugal
| | - Philipp Mitteroecker
- Department of Evolutionary Biology, Unit for Theoretical Biology, University of Vienna, Djerassiplatz 1, 1030, Vienna, Austria.
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23
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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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Wells JCK, Pomeroy E, Stock JT. Evolution of Lactase Persistence: Turbo-Charging Adaptation in Growth Under the Selective Pressure of Maternal Mortality? Front Physiol 2021; 12:696516. [PMID: 34497534 PMCID: PMC8419441 DOI: 10.3389/fphys.2021.696516] [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: 04/16/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
The emergence of the capacity to digest milk in some populations represents a landmark in human evolution, linking genetic change with a component of niche construction, namely dairying. Alleles promoting continued activity of the enzyme lactase through the life-course (lactase persistence) evolved in several global regions within the last 7,000 years. In some European regions, these alleles underwent rapid selection and must have profoundly affected fertility or mortality. Elsewhere, alleles spread more locally. However, the functional benefits underlying the rapid spread of lactase persistence remain unclear. Here, we set out the hypothesis that lactase persistence promoted skeletal growth, thereby offering a generic rapid solution to childbirth complications arising from exposure to ecological change, or to new environments through migration. Since reduced maternal growth and greater neonatal size both increase the risk of obstructed labour, any ecological exposure impacting these traits may increase maternal mortality risk. Over many generations, maternal skeletal dimensions could adapt to new ecological conditions through genetic change. However, this adaptive strategy would fail if ecological change was rapid, including through migration into new niches. We propose that the combination of consuming milk and lactase persistence could have reduced maternal mortality by promoting growth of the pelvis after weaning, while high calcium intake would reduce risk of pelvic deformities. Our conceptual framework provides locally relevant hypotheses to explain selection for lactase persistence in different global regions. For any given diet and individual genotype, the combination of lactase persistence and milk consumption would divert more energy to skeletal growth, either increasing pelvic dimensions or buffering them from worsening ecological conditions. The emergence of lactase persistence among dairying populations could have helped early European farmers adapt rapidly to northern latitudes, East African pastoralists adapt to sudden climate shifts to drier environments, and Near Eastern populations counteract secular declines in height associated with early agriculture. In each case, we assume that lactase persistence accelerated the timescale over which maternal skeletal dimensions could change, thus promoting both maternal and offspring survival. Where lactase persistence did not emerge, birth weight was constrained at lower levels, and this contributes to contemporary variability in diabetes risk.
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Affiliation(s)
- Jonathan C K Wells
- Childhood Nutrition Research Centre, Population Policy and Practice Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Emma Pomeroy
- Department of Archaeology, University of Cambridge, Cambridge, United Kingdom
| | - Jay T Stock
- Department of Anthropology, University of Western Ontario, London, ON, Canada.,Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany
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25
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Moffett EA. Sexual dimorphism in the size and shape of the non-obstetric pelvis across anthropoids. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 176:402-421. [PMID: 34453450 DOI: 10.1002/ajpa.24398] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 04/26/2021] [Accepted: 07/20/2021] [Indexed: 11/06/2022]
Abstract
OBJECTIVES The presence of sexual dimorphism in the birth canals of anthropoid primates is well documented, and birth canal dimorphism tends to be especially robust among species that give birth to relatively large neonates. However, it is less clear whether birth canal dimorphism is accompanied by dimorphism in parts of the pelvis not directly under selection for birth, particularly including bi-iliac breadth, biactetabular breadth, lengths of the ischium and ilium, and 3D shape. This study investigates the patterns of dimorphism among anthropoid primates in those parts of the pelvis which do not directly contribute to the bony birth canal, here termed the non-obstetric pelvis. METHODS 3D landmark data were collected on the bony pelves of 899 anthropoid primates. Specifically, landmark data were collected on parts of the pelvis not thought to be directly involved in selection for parturition, including portions of the posterior and superior ilium, acetabulum, and lateral ischium. Principal components analysis and Euclidean distance matrix analysis were used to ascertain sexual dimorphism in pelvic sizes and shapes within each species. RESULTS Results show that dimorphism in non-obstetric pelvic size and shape exists across anthropoids, just as is seen in the birth canal. However, the magnitude of dimorphism in non-obstetric pelvic shape tends to be greater among anthropoid species that give birth to relatively large neonates compared with those birthing smaller neonates relative to maternal pelvic size. CONCLUSIONS Though all anthropoids included in the study show some degree of sexual dimorphism in non-obstetric pelvic size and/or shape, species which give birth to large neonates relative to maternal pelvic size have the highest levels of dimorphism in pelvic shape. Moreover, the magnitude of dimorphism in certain parts of the non-obstetric pelvis mirrors patterns seen in the birth canal. The results of this study are promising for ascertaining pelvic dimorphism and relative neonate size in fossil primates, particularly in fragmentary remains which do not preserve a complete bony birth canal.
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Affiliation(s)
- Elizabeth A Moffett
- Department of Clinical Anatomy and Osteopathic Principles, Rocky Vista University, Parker, Colorado, USA
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26
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Lassek WD, Gaulin SJC. Does Nubility Indicate More Than High Reproductive Value? Nubile Primiparas' Pregnancy Outcomes in Evolutionary Perspective. EVOLUTIONARY PSYCHOLOGY 2021; 19:14747049211039506. [PMID: 34524917 PMCID: PMC10355305 DOI: 10.1177/14747049211039506] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 07/27/2021] [Accepted: 07/28/2021] [Indexed: 11/16/2022] Open
Abstract
The idea that human males are most strongly attracted to traits that peak in women in the nubile age group raises the question of how well women in that age group contend with the potential hazards of a first pregnancy. Using data for 1.7 million first births from 1990 U.S. natality and mortality records, we compared outcomes for women with first births (primiparas) aged 16-20 years (when first births typically occur in forager and subsistence groups) with those aged 21-25 years. The younger primiparas had a much lower risk of potentially life-threatening complications of labor and delivery and, when evolutionarily novel risk factors were controlled, fetuses which were significantly more likely to survive despite lower birth weights. Thus, nubile primiparas were more likely to have a successful reproductive outcome defined in an evolutionarily relevant way (an infant of normal birth weight and gestation, surviving to one year, and delivered without a medically necessary cesarean delivery). This suggests that prior to the widespread availability of surgical deliveries, men who mated with women in the nubile age group would have reaped the benefit of having a reproductive partner more likely to have a successful first pregnancy.
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Affiliation(s)
- William D. Lassek
- Department of Anthropology, HSSB 2001, University of California, Santa Barbara, CA, USA
| | - Steven J. C. Gaulin
- Department of Anthropology, HSSB 2001, University of California, Santa Barbara, CA, USA
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27
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McGuire JA, Monclova JL, Coariti ACS, Stine CA, Toussaint KC, Munson JM, Dillard DA, De Vita R. Tear propagation in vaginal tissue under inflation. Acta Biomater 2021; 127:193-204. [PMID: 33831574 DOI: 10.1016/j.actbio.2021.03.065] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 03/06/2021] [Accepted: 03/30/2021] [Indexed: 12/21/2022]
Abstract
Vaginal tearing at childbirth is extremely common yet understudied despite the long-term serious consequences on women's health. The mechanisms of vaginal tearing remain unknown, and their knowledge could lead to the development of transformative prevention and treatment techniques for maternal injury. In this study, whole rat vaginas with pre-imposed elliptical tears oriented along the axial direction of the organs were pressurized using a custom-built inflation setup, producing large tear propagation. Large deformations of tears through propagation were analyzed, and nonlinear strains around tears were calculated using the digital image correlation technique. Second harmonic generation microscopy was used to examine collagen fiber organization in mechanically untested and tested vaginal specimens. Tears became increasingly circular under pressure, propagating slowly up to the maximum pressure and then more rapidly. Hoop strains were significantly larger than axial strains and displayed a region- and orientation-dependent response with tear propagation. Imaging revealed initially disorganized collagen fibers that aligned along the axial direction with increasing pressure. Fibers in the near-regions of tear tips aligned toward the hoop direction, hampering tear propagation. Changes in tear geometry, regional strains, and fiber orientation revealed the inherent toughening mechanisms of the vaginal tissue. STATEMENT OF SIGNIFICANCE: Women's reproductive health has historically been understudied despite alarming maternal injury and mortality rates in the world. Maternal injury and disability can be reduced by advancing our limited understanding of the large deformations experienced by women's reproductive organs. This manuscript presents, for the first time, the mechanics of tear propagation in vaginal tissue and changes to the underlying collagen microstructure near to and far from the tear. A novel inflation setup capable of maintaining the in vivo tubular geometry of the vagina while propagating a pre-imposed tear was developed. Toughening mechanisms of the vagina to propagation were examined through measurements of tear geometry, strain distributions, and reorientation of collagen fibers. This research draws from current advances in the engineering science and mechanics fields with the goal of improving maternal health care.
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Affiliation(s)
- Jeffrey A McGuire
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States
| | - Jose L Monclova
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States
| | | | - Caleb A Stine
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States
| | - Kimani C Toussaint
- PROBE Lab, School of Engineering, Brown University, Providence, RI 02912, United States
| | - Jennifer M Munson
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States
| | - David A Dillard
- Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States
| | - Raffaella De Vita
- STRETCH Lab, Department of Biomedical Engineering and Mechanics, Virginia Tech, Blacksburg, VA 24061, United States.
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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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29
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Adegboyega MT, Stamos PA, Hublin JJ, Weaver TD. Virtual reconstruction of the Kebara 2 Neanderthal pelvis. J Hum Evol 2020; 151:102922. [PMID: 33360685 DOI: 10.1016/j.jhevol.2020.102922] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 11/17/2020] [Accepted: 11/18/2020] [Indexed: 12/01/2022]
Abstract
The paucity of well-preserved pelvises in the hominin fossil record has hindered robust analyses of shifts in critical biological processes throughout human evolution. The Kebara 2 pelvis remains one of the best preserved hominin pelvises, providing a rare opportunity to assess Neanderthal pelvic morphology and function. Here, we present two new reconstructions of the Kebara 2 pelvis created from CT scans of the right hip bone and sacrum. For both reconstructions, we proceeded as follows. First, we virtually reconstructed the right hip bone and the sacrum by repositioning the fragments of the hip bone and sacrum. Then, we created a mirrored copy of the right hip bone to act as the left hip bone. Next, we 3D printed the three bones and physically articulated them. Finally, we used fiducial points collected from the physically articulated models to articulate the hip bones and sacrum in virtual space. Our objectives were to (1) reposition misaligned fragments, particularly the ischiopubic ramus; (2) create a 3D model of a complete pelvis; and (3) assess interobserver reconstruction variation. These new reconstructions show that, in comparison with previous measurements, Kebara 2 possessed a higher shape index (maximum anteroposterior length/maximum mediolateral width) for the pelvic inlet and perhaps the outlet and a more anteriorly positioned sacral promontory and pubic symphysis relative to the acetabula. The latter differences result in a lower ratio between the distances anterior and posterior to the anterior margins of the acetabula. Generally, the new reconstructions tend to accentuate features of the Kebara 2 pelvis--the long superior pubic ramus and anteriorly positioned pelvic inlet--that have already been discussed for Kebara 2 and other Neanderthals.
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Affiliation(s)
- Mayowa T Adegboyega
- Department of Anthropology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA.
| | - Peter A Stamos
- Department of Anthropology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA; Department of Organismal Biology and Anatomy, University of Chicago, 1027 E. 57th Street / Anatomy 201, Chicago, IL, 60637, USA
| | - Jean-Jacques Hublin
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
| | - Timothy D Weaver
- Department of Anthropology, University of California, 1 Shields Avenue, Davis, CA, 95616, USA; Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
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30
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Torres-Tamayo N, Martelli S, Schlager S, García-Martínez D, Sanchis-Gimeno JA, Mata-Escolano F, Nalla S, Ogihara N, Oishi M, Bastir M. Assessing thoraco-pelvic covariation in Homo sapiens and Pan troglodytes: A 3D geometric morphometric approach. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 173:514-534. [PMID: 32864759 DOI: 10.1002/ajpa.24103] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 05/31/2020] [Accepted: 06/11/2020] [Indexed: 12/18/2022]
Abstract
OBJECTIVES Understanding thoraco-pelvic integration in Homo sapiens and their closest living relatives (genus Pan) is of great importance within the context of human body shape evolution. However, studies assessing thoraco-pelvic covariation across Hominoidea species are scarce, although recent research would suggest shared covariation patterns in humans and chimpanzees but also species-specific features, with sexual dimorphism and allometry influencing thoraco-pelvic covariation in these taxa differently. MATERIAL AND METHODS N = 30 adult H. sapiens and N = 10 adult Pan troglodytes torso 3D models were analyzed using 3D geometric morphometrics and linear measurements. Effects of sexual dimorphism and allometry on thoraco-pelvic covariation were assessed via regression analyses, and patterns of thoraco-pelvic covariation in humans and chimpanzees were computed via Two-Block Partial Least Squares analyses. RESULTS Results confirm the existence of common aspects of thoraco-pelvic covariation in humans and chimpanzees, and also species-specific covariation in H. sapiens that is strongly influenced by sexual dimorphism and allometry. Species-specific covariation patterns in chimpanzees could not be confirmed because of the small sample size, but metrics point to a correspondence between the most caudal ribs and iliac crest morphology that would be irrespective of sex. CONCLUSIONS This study suggests that humans and chimpanzees share common aspects of thoraco-pelvic covariation but might differ in others. In humans, torso integration is strongly influenced by sexual dimorphism and allometry, whilst in chimpanzees it may not be. This study also highlights the importance not only of torso widths but also of torso depths when describing patterns of thoraco-pelvic covariation in primates. Larger samples are necessary to support these interpretations.
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Affiliation(s)
- Nicole Torres-Tamayo
- Departamento de Paleobiología, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain.,GIAVAL Research Group, Department of Anatomy and Human Embryology, University of Valencia, Valencia, Spain
| | - Sandra Martelli
- UCL Centre for Integrative Anatomy (CIA), Department of Cell and Developmental Biology, Faculty of Life Sciences, London, UK
| | - Stefan Schlager
- Biological Anthropology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Daniel García-Martínez
- Departamento de Paleobiología, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain.,Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain
| | | | | | - Shahed Nalla
- GIAVAL Research Group, Department of Anatomy and Human Embryology, University of Valencia, Valencia, Spain.,Department of Human Anatomy and Physiology, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa
| | - Naomichi Ogihara
- Department of Biological Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Motoharu Oishi
- Laboratory of Anatomy 1, School of Veterinary Medicine, Azabu University, Sagamihara, Japan
| | - Markus Bastir
- Departamento de Paleobiología, Museo Nacional de Ciencias Naturales (CSIC), Madrid, Spain
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31
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Covariation of fetal skull and maternal pelvis during the perinatal period in rhesus macaques and evolution of childbirth in primates. Proc Natl Acad Sci U S A 2020; 117:21251-21257. [PMID: 32817513 DOI: 10.1073/pnas.2002112117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A large brain combined with an upright posture in humans has resulted in a high cephalopelvic proportion and frequently obstructed labor. Fischer and Mitteroecker [B. Fischer, P. Mitteroecker, Proc. Natl. Acad. Sci. U.S.A. 112, 5655-5660 (2015)] proposed that the morphological covariations between the skull and pelvis could have evolved to ameliorate obstructed labor in humans. The availability of quantitative data of such covariation, especially of the fetal skull and maternal pelvis, however, is still scarce. Here, we present direct evidence of morphological covariations between the skull and pelvis using actual mother-fetus dyads during the perinatal period of Macaca mulatta, a species that exhibits cephalopelvic proportions comparable to modern humans. We analyzed the covariation of the three-dimensional morphology of the fetal skull and maternal pelvis using computed tomography-based models. The covariation was mostly observed at the pelvic locations related to the birth canal, and the forms of the birth canal and fetal skull covary in such a way that reduces obstetric difficulties. Therefore, cephalopelvic covariation could have evolved not only in humans, but also in other primate taxa in parallel, or it could have evolved already in the early catarrhines.
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32
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Frémondière P, Lacoste R, Rachid L. Un cas d’accouchement en occipito-pubien chez Pan troglodytes. REVUE DE PRIMATOLOGIE 2020. [DOI: 10.4000/primatologie.7036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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33
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Snell-Rood E, Snell-Rood C. The developmental support hypothesis: adaptive plasticity in neural development in response to cues of social support. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190491. [PMID: 32475336 PMCID: PMC7293157 DOI: 10.1098/rstb.2019.0491] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/20/2020] [Indexed: 12/13/2022] Open
Abstract
Across mammals, cues of developmental support, such as touching, licking or attentiveness, stimulate neural development, behavioural exploration and even overall body growth. Why should such fitness-related traits be so sensitive to developmental conditions? Here, we review what we term the 'developmental support hypothesis', a potential adaptive explanation of this plasticity. Neural development can be a costly process, in terms of time, energy and exposure. However, environmental variability may sometimes compromise parental care during this costly developmental period. We propose this environmental variation has led to the evolution of adaptive plasticity of neural and behavioural development in response to cues of developmental support, where neural development is stimulated in conditions that support associated costs. When parental care is compromised, offspring grow less and adopt a more resilient and stress-responsive strategy, improving their chances of survival in difficult conditions, similar to existing ideas on the adaptive value of early-life programming of stress. The developmental support hypothesis suggests new research directions, such as testing the adaptive value of reduced neural growth and metabolism in stressful conditions, and expanding the range of potential cues animals may attend to as indicators of developmental support. Considering evolutionary and ecologically appropriate cues of social support also has implications for promoting healthy neural development in humans. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.
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Affiliation(s)
- Emilie Snell-Rood
- Department of Ecology, Evolution and Behavior, University of Minnesota, 1479 Gortner Avenue, Gortner 140, St Paul, MN 55108, USA
| | - Claire Snell-Rood
- School of Public Health, University of California, Berkeley, Berkeley, CA, USA
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34
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Ricklan SJ, Decrausaz SL, Wells JCK, Stock JT. Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma. Am J Hum Biol 2020; 33:e23451. [PMID: 32567787 DOI: 10.1002/ajhb.23451] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 05/14/2020] [Accepted: 05/15/2020] [Indexed: 12/31/2022] Open
Abstract
OBJECTIVES The "obstetrical dilemma" hypothesis assumes that the modern human female pelvis serves two discrete functions: obstetrics and locomotion. We investigate whether these differing functions create observable patterns of morphological covariation and whether those patterns differ by height, weight, and age. This allows evaluation of evidence for canalization and phenotypic plasticity relevant to obstetric and locomotor function among a living female population. METHODS Landmarks (N = 86) were collected and inter-landmark distances were calculated (N = 36) on the pelvis and proximal femur of CT scans of living women aged 20 to 90 years (M = 93) receiving a routine CT scan. Partial least squares and relative SD of eigenvalues analyses were used to evaluate integration overall and within locomotor and obstetric modules, respectively. Ordinary Least Squared regression was used to evaluate scaling relationships between inter-landmark distances and height, weight, and age. RESULTS The obstetric pelvis was significantly less internally integrated than the locomotor pelvis. Many obstetric measurements were constrained in absolute terms relative to height; shorter women had relatively larger birth canal dimensions, and several key obstetric dimensions showed relative freedom from height. Lower weight women had some relatively larger obstetric and locomotor dimensions. Regarding age, younger women showed a few relatively larger outlet dimensions. CONCLUSIONS This study suggests that the obstetric pelvis and the locomotor pelvis function are morphologically distinct, with the obstetric pelvis showing relatively greater flexibility. These relationships between relative constraints support the hypothesis that the modern female pelvis shows evidence of both canalization and phenotypic plasticity in obstetric and locomotor structures.
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Affiliation(s)
- Sarah J Ricklan
- Department of Archaeology, University of Cambridge, Cambridge, UK.,New York University Grossman School of Medicine, New York, New York, USA
| | - Sarah-Louise Decrausaz
- Department of Archaeology, University of Cambridge, Cambridge, UK.,Department of Anthropology, University of Victoria, Victoria, British Columbia, Canada
| | - Jonathan C K Wells
- Childhood Nutrition Research Centre, Population, Policy, and Practice Research and Teaching Department, UCL Great Ormond Street Institute of Child Health, London, UK
| | - Jay T Stock
- Department of Archaeology, University of Cambridge, Cambridge, UK.,Department of Anthropology, Western University, London, Ontario, Canada.,Department of Archaeology, Max Planck Centre for the Science of Human History, Jena, Germany
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35
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Caesarean sections are associated with sonographic determined fetal size from the second trimester onwards. ANTHROPOLOGICAL REVIEW 2020. [DOI: 10.2478/anre-2020-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Human birth represents a critical and life-threatening event in the life of mother and child and is therefore of special importance for anthropological as well as public health research.
Study aims: to analyze the association patterns between fetal biometry and delivery modes from the first trimester onwards.
In this electronic medical record-based study, a dataset of 3408 singleton term birth taking place at the Viennese Danube hospital in Austria. was analyzed. Fetal biometry was reconstructed by the results of three ultrasound examinations carried out at the 11th/12th, 20th/21th and 32th/33thweek of gestation. In detail, crown-rump length, biparietal diameter, fronto-occipital diameter, head circumference, abdominal trans-verse diameter, abdominal sagittal diameter, abdominal circumference, and femur length were determined. Birth weight, birth length and head circumference were measured immediately after birth. Four delivery modes were compared: spontaneous vaginal birth, instrumental vaginal birth, planned cesarean section and emergency cesarean section.
The total cesarean section rate was 10.2%. Fetal biometry and newborn size differed significantly between the four delivery modes. From the second trimester onward, head circumferences were significantly larger (p=0.005) among fetuses delivered by instrumental delivery or emergency cesarean section than among fetuses delivered by spontaneous vaginal birth. The fetal abdominal dimensions during the third trimester were significantly largest (p=0.001) among fetuses delivered by emergency cesarean section. In comparison to spontaneous vaginal delivery the risk to require instrumental delivery increased significantly with increasing fetal head dimensions at the second (p=0.019) and third trimester(p=0.032) independent of maternal somatic factors. The risk of emergency CS increased significantly with increasing head dimensions (p=0.030) as well as abdominal dimensions (p=0.001) at the third trimester and newborn size (p=0.002), also independently of maternal somatic factors.
In general, larger fetuses are on an increased risk of experiencing instrumental delivery or emergency caesarean section. This association between fetal size and delivery mode is detectable from the second trimester onwards.
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36
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Affiliation(s)
- Cara Ocobock
- Department of Anthropology University Notre Dame Notre Dame IN 46556 USA
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37
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Canini M, Cavoretto P, Scifo P, Pozzoni M, Petrini A, Iadanza A, Pontesilli S, Scotti R, Candiani M, Falini A, Baldoli C, Della Rosa PA. Subcortico-Cortical Functional Connectivity in the Fetal Brain: A Cognitive Development Blueprint. Cereb Cortex Commun 2020; 1:tgaa008. [PMID: 34296089 PMCID: PMC8152909 DOI: 10.1093/texcom/tgaa008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 02/24/2020] [Accepted: 03/25/2020] [Indexed: 12/19/2022] Open
Abstract
Recent evidence has shown that patterns of cortico-cortical functional synchronization are consistently traceable by the end of the third trimester of pregnancy. The involvement of subcortical structures in early functional and cognitive development has never been explicitly investigated, notwithstanding their pivotal role in different cognitive processes. We address this issue by exploring subcortico-cortical functional connectivity at rest in a group of normally developing fetuses between the 25th and 32nd weeks of gestation. Results show significant functional coupling between subcortical nuclei and cortical networks related to: (i) sensorimotor processing, (ii) decision making, and (iii) learning capabilities. This functional maturation framework unearths a Cognitive Development Blueprint, according to which grounding cognitive skills are planned to develop with higher ontogenetic priority. Specifically, our evidence suggests that a newborn already possesses the ability to: (i) perceive the world and interact with it, (ii) create salient representations for the selection of adaptive behaviors, and (iii) store, retrieve, and evaluate the outcomes of interactions, in order to gradually improve adaptation to the extrauterine environment.
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Affiliation(s)
- Matteo Canini
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Paolo Cavoretto
- Department of Gynecology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Paola Scifo
- Department of Nuclear Medicine, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Mirko Pozzoni
- Department of Gynecology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Alessandro Petrini
- Department of Computer Science, Università degli Studi Milano, 20122 Milan, Italy
| | - Antonella Iadanza
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Silvia Pontesilli
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Roberta Scotti
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Massimo Candiani
- Department of Gynecology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Andrea Falini
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
| | - Cristina Baldoli
- Department of Neuroradiology, San Raffaele Scientific Institute, 20132 Milan, Italy
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Cheyney M, Davis-Floyd R. Birth and the Big Bad Wolf: Biocultural Evolution and Human Childbirth, Part 1. INTERNATIONAL JOURNAL OF CHILDBIRTH 2020. [DOI: 10.1891/ijcbirth-d-19-00030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In this two-part article, we reflect on the evolution of human childbirth by combining our respective expertise in folklore and interpretive anthropology (Davis-Floyd) and physiologic birth (Cheyney). In Part 1, we follow six little folkloric pigs from the beginnings of human history through to the present, adapting the well-known tale of “The Three Little Pigs and the Big Bad Wolf.” Using this tale as a metaphorical device, we explore complex relationships between humans and nature, society, and childbirth through a description of the six basic subsistence strategies humans have developed over time—foraging, horticulture, agriculture, pastoralism, industrialism, and the technocracy, reflecting on how these ways of life connect to birthing practices. We argue that despite vast cultural differences in the treatment of birth—including those few cultures where solitary birth is valued—premodern, pre-industrial birthways had much in common, such as labor accompaniment, upright positions, and freedom of movement during labor and birth. These similarities were supplanted during the Industrial Revolution with the subsequent growth of technocratic societies and replaced by an also very similar set of birthing practices. However, these technocratic approaches do very little to support, and often even undermine, our evolved birthing biologies. Throughout, we use the Big Bad Wolf as a metaphor for the wild, untamed, and sometimes intense power of nature (and also of unmedicated birth), and ask, what does the Big Bad Wolf have to teach us about how we support and perform childbirth today?
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Parncutt R. Mother Schema, Obstetric Dilemma, and the Origin of Behavioral Modernity. Behav Sci (Basel) 2019; 9:E142. [PMID: 31817739 PMCID: PMC6960940 DOI: 10.3390/bs9120142] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 11/29/2019] [Accepted: 12/02/2019] [Indexed: 11/29/2022] Open
Abstract
What triggered the emergence of uniquely human behaviors (language, religion, music) some 100,000 years ago? A non-circular, speculative theory based on the mother-infant relationship is presented. Infant "cuteness" evokes the infant schema and motivates nurturing; the analogous mother schema (MS) is a multimodal representation of the carer from the fetal/infant perspective, motivating fearless trust. Prenatal MS organizes auditory, proprioceptive, and biochemical stimuli (voice, heartbeat, footsteps, digestion, body movements, biochemicals) that depend on maternal physical/emotional state. In human evolution, bipedalism and encephalization led to earlier births and more fragile infants. Cognitively more advanced infants survived by better communicating with and motivating (manipulating) mothers and carers. The ability to link arbitrary sound patterns to complex meanings improved (proto-language). Later in life, MS and associated emotions were triggered in ritual settings by repetitive sounds and movements (early song, chant, rhythm, dance), subdued light, dull auditory timbre, psychoactive substances, unusual tastes/smells and postures, and/or a feeling of enclosure. Operant conditioning can explain why such actions were repeated. Reflective consciousness emerged as infant-mother dyads playfully explored intentionality (theory of mind, agent detection) and carers predicted and prevented fatal infant accidents (mental time travel). The theory is consistent with cross-cultural commonalities in altered states (out-of-body, possessing, floating, fusing), spiritual beings (large, moving, powerful, emotional, wise, loving), and reports of strong musical experiences and divine encounters. Evidence is circumstantial and cumulative; falsification is problematic.
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Affiliation(s)
- Richard Parncutt
- Centre for Systematic Musicology, University of Graz, 8010 Graz, Austria
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40
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Wells JCK. Could consanguineous marriage provide a cultural alleviation for the obstetric dilemma? Med Hypotheses 2019; 134:109424. [PMID: 31654884 DOI: 10.1016/j.mehy.2019.109424] [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: 07/30/2019] [Revised: 09/27/2019] [Accepted: 10/09/2019] [Indexed: 11/18/2022]
Abstract
In placental mammals, a poor fit between the physical dimensions of the fetus and maternal pelvis increases the likelihood of obstructed labour. This problem is especially relevant to humans, as our species demonstrates both unique adaptations in pelvic shape and structure associated with bipedalism, and fetal encephalization. Natural selection is expected to have favoured adaptations that reduce the chances of such mismatch within individual mother-offspring dyads. Here, I hypothesise that the cultural practice of consanguineous marriage may have been favoured, on account of increasing the genetic similarity between mothers and offspring and hence the correlation between maternal and fetal physical dimensions. These benefits could be amplified if consanguineous marriage was accompanied by assortative mating for height. An additional benefit of consanguineous marriage for childbirth is the slight reduction in birth size of such offspring compared to non-consanguineous unions. Although the offspring of consanguineous unions have elevated risks of morbidity and mortality, these risks are moderate and the practice could still have been favoured by selection if the reduction in maternal mortality was greater than the increased mortality among individual offspring. This hypothesis could be tested directly by investigating whether rates of obstructed labour are lower in individuals and populations practising consanguineous marriage. At a broader level, phylogenetic analysis could be conducted to test whether consanguineous marriage appears to have originated in the areas where intensive agriculture was first practiced, as adult height typically fell in such populations, potentially exacerbating the risk of obstructed labour.
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Affiliation(s)
- Jonathan C K Wells
- Childhood Nutrition Research Centre, Population, Policy and Practice Research and Teaching Programme, UCL Great Ormond Street Institute of Child Health, 30 Guilford Street, London WC1N 1EH, WC, UK.
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41
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Abstract
Hominin birth mechanics have been examined and debated from limited and often fragmentary fossil pelvic material. Some have proposed that birth in the early hominin genus Australopithecus was relatively easy and ape-like, while others have argued for a more complex, human-like birth mechanism in australopiths. Still others have hypothesized a unique birth mechanism, with no known modern equivalent. Preliminary work on the pelvis of the recently discovered 1.98 million-year-old hominin Australopithecus sediba found it to possess a unique combination of Homo and Australopithecus-like features. Here, we create a composite pelvis of Australopithecus sediba to reconstruct the birth process in this early hominin. Consistent with other hominin species, including modern humans, the fetus would enter the pelvic inlet in a transverse direction. However, unlike in modern humans, the fetus would not need additional rotations to traverse the birth canal. Further fetal rotation is unnecessary even with a Homo-like pelvic midplane expansion, not seen in earlier hominin species. With a birth canal shape more closely associated with specimens from the genus Homo and a lack of cephalopelvic or shoulder constraints, we therefore find evidence to support the hypothesis that the pelvic morphology of Australopithecus sediba is a result of locomotor, rather than strictly obstetric constraints.
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Blagrove M, Hale S, Lockheart J, Carr M, Jones A, Valli K. Testing the Empathy Theory of Dreaming: The Relationships Between Dream Sharing and Trait and State Empathy. Front Psychol 2019; 10:1351. [PMID: 31281278 PMCID: PMC6596280 DOI: 10.3389/fpsyg.2019.01351] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 05/24/2019] [Indexed: 12/30/2022] Open
Abstract
In general, dreams are a novel but realistic simulation of waking social life, with a mixture of characters, motivations, scenarios, and positive and negative emotions. We propose that the sharing of dreams has an empathic effect on the dreamer and on significant others who hear and engage with the telling of the dream. Study 1 tests three correlations that are predicted by the theory of dream sharing and empathy: that trait empathy will be correlated with frequency of telling dreams to others, with frequency of listening to others' dreams, and with trait attitude toward dreams (ATD) (for which higher scores indicate positive attitude). 160 participants completed online the Toronto Empathy Questionnaire and the Mannheim Dream Questionnaire. Pearson partial correlations were conducted, with age and sex partialled out. Trait empathy was found to be significantly associated with the frequency of listening to the dreams of others, frequency of telling one's own dreams to others, and attitude toward dreams. Study 2 tests the effects of discussing dreams on state empathy, using an adapted version of the Shen (2010) state empathy scale, for 27 pairs of dream sharers and discussers. Dream discussion followed the stages of the Ullman (1996) dream appreciation technique. State empathy of the dream discusser toward the dream sharer was found to increase significantly as a result of the dream discussion, with a medium effect size, whereas the dream sharer had a small decrease in empathy toward the discusser. A proposed mechanism for these associations and effects is taken from the robust findings in the literature that engagement with literary fiction can induce empathy toward others. We suggest that the dream acts as a piece of fiction that can be explored by the dreamer together with other people, and can thus induce empathy about the life circumstances of the dreamer. We discuss the speculation that the story-like characteristics of adult human dreams may have been selected for in human evolution, including in sexual selection, as part of the selection for emotional intelligence, empathy, and social bonding.
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Affiliation(s)
- Mark Blagrove
- Department of Psychology, Swansea University, Swansea, United Kingdom
| | - Sioned Hale
- Department of Psychology, Swansea University, Swansea, United Kingdom
| | - Julia Lockheart
- Swansea College of Art, University of Wales Trinity Saint David, Swansea, United Kingdom.,Goldsmiths, University of London, London, United Kingdom
| | - Michelle Carr
- Department of Psychology, Swansea University, Swansea, United Kingdom
| | - Alex Jones
- Department of Psychology, Swansea University, Swansea, United Kingdom
| | - Katja Valli
- Department of Psychology, University of Turku, Turku, Finland.,Department of Cognitive Neuroscience and Philosophy, The University of Skövde, Skövde, Sweden
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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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44
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Jones BP, Williams NJ, Saso S, Thum M, Quiroga I, Yazbek J, Wilkinson S, Ghaem‐Maghami S, Thomas P, Smith JR. Uterine transplantation in transgender women. BJOG 2019; 126:152-156. [PMID: 30125449 PMCID: PMC6492192 DOI: 10.1111/1471-0528.15438] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2018] [Indexed: 11/28/2022]
Affiliation(s)
- BP Jones
- West London Gynaecological Cancer CentreHammersmith HospitalImperial College NHS TrustLondonUK
- Department of Surgery and CancerImperial College LondonLondonUK
| | - NJ Williams
- Department of Politics, Philosophy and ReligionLancaster UniversityLancasterUK
| | - S Saso
- West London Gynaecological Cancer CentreHammersmith HospitalImperial College NHS TrustLondonUK
- Department of Surgery and CancerImperial College LondonLondonUK
| | - M‐Y Thum
- Department of Surgery and CancerImperial College LondonLondonUK
- Lister Fertility ClinicThe Lister HospitalLondonUK
| | - I Quiroga
- The Oxford Transplant CentreThe Churchill HospitalOxford University Hospitals NHS TrustOxfordUK
| | - J Yazbek
- West London Gynaecological Cancer CentreHammersmith HospitalImperial College NHS TrustLondonUK
- Department of Surgery and CancerImperial College LondonLondonUK
| | - S Wilkinson
- Department of Politics, Philosophy and ReligionLancaster UniversityLancasterUK
| | - S Ghaem‐Maghami
- West London Gynaecological Cancer CentreHammersmith HospitalImperial College NHS TrustLondonUK
- Department of Surgery and CancerImperial College LondonLondonUK
| | - P Thomas
- Brighton Gender ClinicNuffield Health HospitalBrightonUK
| | - JR Smith
- West London Gynaecological Cancer CentreHammersmith HospitalImperial College NHS TrustLondonUK
- Department of Surgery and CancerImperial College LondonLondonUK
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45
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Abstract
Maternal mortality remains one of the leading causes of death in women of reproductive age in developing countries, and a major concern in some developed countries. It is puzzling why such a condition has not been reduced in frequency, if not eliminated, in the course of evolution. Maternal mortality is a complex phenomenon caused by several physiological and physical factors. Among the physical factors, maternal mortality due to fetopelvic disproportion remains controversial. Several explanations including evolution of bipedal locomotion, rapid brain growth, and nutritional changes and life style changes in settler communities have been proposed. The influences of human reproductive biology and sexual selection have rarely been considered to explain why maternal mortality persisted through human evolution. We entertain the hypothesis that irrespective of the causes, the risks of all factors causing maternal mortality would be aggravated by disassortative mating, specifically male preference for younger females who are generally small statured and at higher risk of obstetric complications. Maternal mortality arising due to sexual selection and mate choice would have the long-term effect of driving widowers toward younger women, often resulting in "child marriage," which still remains a significant cause of maternal mortality globally. Evolutionarily, such a male driven mating system in polygamous human populations would have prolonged the persistence of maternal mortality despite selection acting against it. The effects may extend beyond maternal mortality because male-mate choice driven maternal mortality would reduce average reproductive life spans of women, thus influencing the evolution of menopause.
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Affiliation(s)
- Santosh Jagadeeshan
- 1 Department of Biology, McMaster University, Hamilton, Canada.,2 Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada
| | - Alyssa K Gomes
- 1 Department of Biology, McMaster University, Hamilton, Canada
| | - Rama S Singh
- 1 Department of Biology, McMaster University, Hamilton, Canada
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46
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Betti L, Manica A. Human variation in the shape of the birth canal is significant and geographically structured. Proc Biol Sci 2018; 285:20181807. [PMID: 30355714 PMCID: PMC6234894 DOI: 10.1098/rspb.2018.1807] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 10/03/2018] [Indexed: 11/12/2022] Open
Abstract
The human birth canal shows a tight fit with the size of the neonate, which can lead to obstetric complications. This is not the case in other apes, and has been explained as the outcome of conflicting evolutionary pressures for bipedal locomotion and parturition of a highly encephalized fetus. Despite the suggested evolutionary constraints on the female pelvis, we show that women are, in fact, extremely variable in the shape of the bony birth canal, with human populations having differently shaped pelvic canals. Neutral evolution through genetic drift and differential migration are largely responsible for the observed pattern of morphological diversity, which correlates well with neutral genetic diversity. Climatic adaptation might have played a role, albeit a minor one, with populations from colder regions showing a more transversally oval shape of the canal inlet. The significant extent of canal shape variation among women from different regions of the world has important implications for modern obstetric practice in multi-ethnic societies, as modern medical understanding has been largely developed on studies of European women.
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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, UK
| | - Andrea Manica
- Department of Zoology, University of Cambridge, Cambridge, UK
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47
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Wells JCK, Wibaek R, Poullas M. The Dual Burden of Malnutrition Increases the Risk of Cesarean Delivery: Evidence From India. Front Public Health 2018; 6:292. [PMID: 30386761 PMCID: PMC6199394 DOI: 10.3389/fpubh.2018.00292] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Accepted: 09/24/2018] [Indexed: 11/23/2022] Open
Abstract
Background: Among contemporary human populations, rates of cesarean delivery vary substantially, making it difficult to know if the procedure is inadequately available, or used excessively relative to medical need. A much-cited evolutionary hypothesis attributed birth complications to an “obstetric dilemma,” resulting from antagonistic selective pressures acting on maternal pelvic dimensions and fetal brain growth during hominin evolution. However, the childbirth challenges experienced by living humans may not be representative of those in the past, and may vary in association with trends in ecological conditions. We hypothesized that variability in maternal phenotype (height and nutritional status) may contribute to the risk of cesarean delivery. In many populations, high levels of child stunting contribute to a high frequency of short adult stature, while obesity is also becoming more common. The combination of short maternal stature and maternal overweight or obesity may substantially increase the risk of cesarean delivery. Methods: Using data from two large Indian health surveys from 2005–6 to 2015–2016, we tested associations of maternal somatic phenotype (short stature, overweight) with the risk of cesarean delivery, adjusting for confounding factors such as maternal age, birth order, rural/urban location, wealth and offspring sex. Results: Secular trends in maternal body mass index between surveys were greater than trends in height. Maternal short stature and overweight both increased the risk of cesarean delivery, most strongly when jointly present within individual women. These associations were independent of birth order, wealth, maternal age and rural/urban location. Secular trends in maternal phenotype explained 18% of the increase in cesarean rate over 10 years. Conclusion: Our results highlight how the emerging dual burden of malnutrition (persisting short adult stature which reflects persistent child stunting; increasing overweight in adults) is likely to impact childbirth in low and middle-income countries.
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Affiliation(s)
- Jonathan C K Wells
- Childhood Nutrition Research Centre, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
| | - Rasmus Wibaek
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark.,Clinical Epidemiology, Steno Diabetes Center Copenhagen, Gentofte, Denmark
| | - Marios Poullas
- Childhood Nutrition Research Centre, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
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48
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Torres-Tamayo N, García-Martínez D, Nalla S, Barash A, Williams SA, Blanco-Pérez E, Mata Escolano F, Sanchis-Gimeno JA, Bastir M. The torso integration hypothesis revisited in Homo sapiens: Contributions to the understanding of hominin body shape evolution. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2018; 167:777-790. [PMID: 30259957 DOI: 10.1002/ajpa.23705] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 08/04/2018] [Accepted: 08/09/2018] [Indexed: 01/08/2023]
Abstract
OBJECTIVES Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hominins and other primates (torso integration hypothesis). However, recent studies suggest that sexual dimorphism could challenge this assumption in Homo sapiens. We test the torso integration hypothesis in two modern human populations, both considering and excluding the effect of sexual dimorphism. We further assess covariation patterns between different thoracic and pelvic levels, and we explore the allometric effects on torso shape variation. MATERIAL AND METHODS A sex-balanced sample of 50 anatomically connected torsos (25 Mediterraneans, 25 Sub-Saharan Africans) was segmented from computed tomography scans. We compared the maximum medio-lateral width at seventh-ninth rib levels with pelvic bi-iliac breadth in males and females within both populations. We measured 1,030 (semi)landmarks on 3D torso models, and torso shape variation, mean size and shape comparisons, thoraco-pelvic covariation and allometric effects were quantified through 3D geometric morphometrics. RESULTS Females show narrow thoraces and wide pelves and males show wide thoraces and narrow pelves, although this trend is more evident in Mediterraneans than in Sub-Saharans. Equal thoracic and pelvic widths, depths and curvatures were found in absence of sexual dimorphism. The highest strength of covariation was found between the lowest rib levels and the ilia, and allometric analyses showed that smaller torsos were wider than larger torsos. CONCLUSIONS This is the first study testing statistically the torso integration hypothesis in anatomically connected torsos. We propose a new and more complex torso integration model in H. sapiens with sexual dimorphism leading to different thoracic and pelvic widths and curvatures. These findings have important implications in hominin body shape reconstructions.
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Affiliation(s)
| | | | - Shahed Nalla
- Department of Human Anatomy and Physiology, Faculty of Health Sciences, University of Johannesburg, Johannesburg, South Africa.,Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Alon Barash
- Faculty of Medicine, Bar-Ilan University, Ramat Gan, Israel
| | - Scott A Williams
- Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, Johannesburg, South Africa.,Center for the Study of Human Origins, Department of Anthropology, New York University, New York, New York.,New York Consortium in Evolutionary Primatology, New York, New York
| | | | - Federico Mata Escolano
- CT and MRI Unit, ERESA, Department of Radiology, General University Hospital, Valencia, Spain
| | - Juan Alberto Sanchis-Gimeno
- Department of Radiology, Hospital de La Ribera, Valencia, Spain.,Department of Anatomy and Human Embryology, Faculty of Medicine, University of Valencia, Valencia, Spain
| | - Markus Bastir
- Paleoanthropology Group, Museo Nacional de Ciencias Naturales, Madrid, Spain
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49
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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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50
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Zhang G, Srivastava A, Bacelis J, Juodakis J, Jacobsson B, Muglia LJ. Genetic studies of gestational duration and preterm birth. Best Pract Res Clin Obstet Gynaecol 2018; 52:33-47. [PMID: 30007778 PMCID: PMC6290110 DOI: 10.1016/j.bpobgyn.2018.05.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 04/18/2018] [Accepted: 05/04/2018] [Indexed: 01/12/2023]
Abstract
The fine control of birth timing is important to human survival and evolution. A key challenge in studying the mechanisms underlying the regulation of human birth timing is that human parturition is a unique to human event — animal models provide only limited information. The duration of gestation or the risk of preterm birth is a complex human trait under genetic control from both maternal and fetal genomes. Genomic discoveries through genome-wide association (GWA) studies would implicate relevant genes and pathways. Similar to other complex human traits, gestational duration is likely to be influenced by numerous genetic variants of small effect size. The detection of these small-effect genetic variants requires very large sample sizes. In addition, several practical and analytical challenges, in particular the involvement of both maternal and fetal genomes, further complicate the genetic studies of gestational duration and other pregnancy phenotypes. Despite these challenges, large-scale GWA studies have already identified several genomic loci associated with gestational duration or the risk of preterm birth. These genomic discoveries have revealed novel insights about the biology of human birth timing. Expanding genomic discoveries in larger datasets by more refined analytical approaches, together with the functional analysis of the identified genomic loci, will collectively elucidate the biological processes underlying the control of human birth timing.
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Affiliation(s)
- Ge Zhang
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, USA; The Center for Prevention of Preterm Birth, Perinatal Institute, Cincinnati Children's Hospital Medical Center, USA; March of Dimes Prematurity Research Center Ohio Collaborative, USA; Department of Pediatrics, University of Cincinnati College of Medicine, USA.
| | - Amit Srivastava
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, USA; The Center for Prevention of Preterm Birth, Perinatal Institute, Cincinnati Children's Hospital Medical Center, USA; March of Dimes Prematurity Research Center Ohio Collaborative, USA; Department of Pediatrics, University of Cincinnati College of Medicine, USA
| | - Jonas Bacelis
- Department of Obstetrics and Gynecology, Sahlgrenska University Hospital Östra (East), Gothenburg, Sweden
| | - Julius Juodakis
- Department of Obstetrics and Gynecology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Bo Jacobsson
- Department of Obstetrics and Gynecology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden; Department of Genetics and Bioinformatics, Area of Health Data and Digitalisation, Norwegian Institute of Public Health, Oslo, Norway
| | - Louis J Muglia
- Division of Human Genetics, Cincinnati Children's Hospital Medical Center, USA; The Center for Prevention of Preterm Birth, Perinatal Institute, Cincinnati Children's Hospital Medical Center, USA; March of Dimes Prematurity Research Center Ohio Collaborative, USA; Department of Pediatrics, University of Cincinnati College of Medicine, USA
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