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Schou MF, Cornwallis CK. Adaptation to fluctuating temperatures across life stages in endotherms. Trends Ecol Evol 2024:S0169-5347(24)00123-X. [PMID: 38902165 DOI: 10.1016/j.tree.2024.05.012] [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: 10/09/2023] [Revised: 05/16/2024] [Accepted: 05/24/2024] [Indexed: 06/22/2024]
Abstract
Accelerating rates of climate change have intensified research on thermal adaptation. Increasing temperature fluctuations, a prominent feature of climate change, means that the persistence of many species depends on both heat and cold tolerance across the entire life cycle. In endotherms, research has focused on specific life stages, with changes in thermoregulation across life rarely being examined. Consequently, there is a need to (i) analyse how heat and cold tolerance mechanisms coevolve, and (ii) test whether antagonistic effects between heat and cold tolerance across different life stages limit thermal adaptation. Information on genes influencing heat and cold tolerance and how they are expressed through life will enable more accurate modelling of species vulnerabilities to future climatic volatility.
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Affiliation(s)
- Mads F Schou
- Department of Biology, Aarhus University, 8000 Aarhus, Denmark.
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2
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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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3
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Suárez J. Scrutinizing microbiome determinism: why deterministic hypotheses about the microbiome are conceptually ungrounded. HISTORY AND PHILOSOPHY OF THE LIFE SCIENCES 2024; 46:12. [PMID: 38347271 PMCID: PMC10861753 DOI: 10.1007/s40656-024-00610-0] [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: 01/27/2023] [Accepted: 01/16/2024] [Indexed: 02/15/2024]
Abstract
This paper addresses the topic of determinism in contemporary microbiome research. I distinguish two types of deterministic claims about the microbiome, and I show evidence that both types of claims are present in the contemporary literature. First, the idea that the host genetics determines the composition of the microbiome which I call "host-microbiome determinism". Second, the idea that the genetics of the holobiont (the individual unit composed by a host plus its microbiome) determines the expression of certain phenotypic traits, which I call "microbiome-phenotype determinism". Drawing on the stability of traits conception of individuality (Suárez in Hist Philos Life Sci 42:11, 2020) I argue that none of these deterministic hypotheses is grounded on our current knowledge of how the holobiont is transgenerationally assembled, nor how it expresses its phenotypic traits.
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Affiliation(s)
- Javier Suárez
- BIOETHICS Research Group - Department of Philosophy, University of Oviedo, Oviedo, Spain.
- Institute of Philosophy, Jagiellonian University, Kraków, Poland.
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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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Smith TD, Prufrock KA, DeLeon VB. How to make a vampire. Anat Rec (Hoboken) 2023; 306:2872-2887. [PMID: 36806921 DOI: 10.1002/ar.25179] [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: 01/07/2023] [Revised: 02/01/2023] [Accepted: 02/01/2023] [Indexed: 02/23/2023]
Abstract
Herein, we compared the developmental maturity of the cranium, limbs, and feeding apparatus in a perinatal common vampire bat relative to its mother. In addition, we introduce a method for combining two computed tomographic imaging techniques to three-dimensionally reconstruct endocasts in poorly ossified crania. The Desmodus specimens were scanned using microcomputed tomography (microCT) and diffusible iodine-based contrast-enhanced CT to image bone and soft tissues. Muscles of the jaw and limbs, and the endocranial cavity were segmented using imaging software. Endocranial volume (ECV) of the perinatal Desmodus is 74% of adult ECV. The facial skeletal is less developed (e.g., palatal length 60% of adult length), but volumes for alveolar crypts/sockets of permanent teeth are nearly identical. The forelimb skeleton is uniformly less ossified than the distal hind limb, with no secondary centers ossified and an entirely cartilaginous carpus. All epiphyseal growth zones are active in the brachium and antebrachium, with the distal radius exhibiting the greatest number of proliferating chondrocytes arranged in columns. The hind limb skeleton is precociously ossified from the knee distally. The musculature of the fore limb, temporalis, and masseter muscles appear weakly developed (6-11% of the adult volume). In contrast, the leg and foot musculature is better developed (23-25% of adult volume), possibly enhancing the newborn's capability to grip the mother's fur. Desmodus is born relatively large, and our results suggest they are born neurally and dentally precocious, with generally underdeveloped limbs, especially the fore limb.
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Affiliation(s)
- Timothy D Smith
- School of Physical Therapy, Slippery Rock University, Slippery Rock, Pennsylvania, USA
| | - Kristen A Prufrock
- Department of Neuroscience, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Valerie B DeLeon
- Department of Anthropology, University of Florida, Gainesville, Florida, USA
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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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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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Taub M, Mazar O, Yovel Y. Pregnancy-related sensory deficits might impair foraging in echolocating bats. BMC Biol 2023; 21:60. [PMID: 36973777 PMCID: PMC10044376 DOI: 10.1186/s12915-023-01557-7] [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: 08/02/2022] [Accepted: 03/02/2023] [Indexed: 03/29/2023] Open
Abstract
BACKGROUND Reproduction entails substantial demands throughout its distinct stages. The mammalian gestation period imposes various energetic costs and movement deficits, but its effects on the sensory system are poorly understood. Bats rely heavily on active sensing, using echolocation to forage in complete darkness, or when lighting is uncertain. We examined the effects of pregnancy on bat echolocation. RESULTS We show that pregnant Kuhl's pipistrelles (Pipistrellus kuhlii) altered their echolocation and flight behavior. Specifically, pregnant bats emitted longer echolocation signals at an ~ 15% lower rate, while flying more slowly and at a lower altitude compared to post-lactating females. A sensorimotor foraging model suggests that these changes could lead to an ~ 15% reduction in hunting performance during pregnancy. CONCLUSIONS Sensory deficits related to pregnancy could impair foraging in echolocating bats. Our study demonstrates an additional cost of reproduction of possible relevance to other sensory modalities and organisms.
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Affiliation(s)
- Mor Taub
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
| | - Omer Mazar
- Sagol School of Neuroscience, Tel Aviv University, 6997801, Tel Aviv, Israel
| | - Yossi Yovel
- School of Zoology, Faculty of Life Sciences, Tel Aviv University, 6997801, Tel Aviv, Israel.
- Sagol School of Neuroscience, Tel Aviv University, 6997801, Tel Aviv, Israel.
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10
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McMichael L, Mclean J, Taylor J, Martinez Y, Meers J. Cleft Palate Syndrome in the Endangered Spectacled Flying Fox ( Pteropus conspicillatus): Implications for Conservation and Comparative Research. Vet Sci 2023; 10:vetsci10010038. [PMID: 36669041 PMCID: PMC9865782 DOI: 10.3390/vetsci10010038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 12/29/2022] [Accepted: 01/03/2023] [Indexed: 01/09/2023] Open
Abstract
Cleft palate syndrome, first observed in the spectacled flying fox population in 1998, has produced sporadic neonatal mortality events over the past two decades, with an estimated incidence of up to 1/1000 births per year. This study presents a rudimentary characterisation of the syndrome, presenting gross pathology of syndromic signs upon visual inspection, a histological examination of palate malformations, and syndrome incidence data representing the past two decades. The syndrome presents with a range of signs, primarily congenital palate malformations ranging from a pinhole cleft to a complete hard and soft palate deficit, resulting in the death or abandonment of neonates shortly after birth. The congenital palate malformations are often associated with claw deformities, wiry facial hair, and in some instances, muscle weakness and neurological signs. The natural occurrence of the lethal congenital orofacial birth defects in the spectacled flying fox presents a unique opportunity for the investigation of putative aetiologies, drawing parallels between bat and other mammalian cleft palate risk factors. Further syndrome investigation has the potential to deliver both biodiversity conservation and comparative veterinary and biomedical outcomes.
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Affiliation(s)
- Lee McMichael
- School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia
- Correspondence:
| | - Jennefer Mclean
- Tolga Bat Rescue and Research Inc., Carrington Road, Atherton, QLD 4883, Australia
| | - Jim Taylor
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD 4810, Australia
| | - Yissu Martinez
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, QLD 4810, Australia
| | - Joanne Meers
- School of Veterinary Science, University of Queensland, Gatton, QLD 4343, Australia
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11
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Tavares WC, Pessôa LM. Pelvic sexual dimorphism and its association with cranial morphology in Neotropical spiny rats (Rodentia, Echimyidae). J MAMM EVOL 2022. [DOI: 10.1007/s10914-022-09625-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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12
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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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Sibeko L, Johns T, Cordeiro LS. Traditional plant use during lactation and postpartum recovery: Infant development and maternal health roles. JOURNAL OF ETHNOPHARMACOLOGY 2021; 279:114377. [PMID: 34192598 DOI: 10.1016/j.jep.2021.114377] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 02/11/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Evidence of phytochemical roles in infant development and maternal recovery offers insights into beneficial functions of traditional plant use during lactation and the postpartum period. Ethnopharmacological research has relevance to global priorities on maternal and child health, to understanding origins and determinants of human self-medication, and for reconciling traditional postpartum practices and mainstream healthcare. AIM OF THE STUDY Present emerging evidence, within evolutionary and socio-cultural contexts, on the role of maternal consumption on transfer of phytochemicals into breast milk with impacts on maternal and child health, and on infant development. Establish current state of knowledge and an ethnopharmacological research agenda that is attentive to cross-cultural and regional differences in postpartum plant use. MATERIALS AND METHODS An extensive literature review using Medline, Scopus, and Web of Science focused on traditional and contemporary use and socio-cultural context, as well as physiological, pharmacological, toxicological, and behavioral activities of plants used medicinally by women during postpartum recovery and lactation. RESULTS The most widely reported postpartum plants show antimicrobial, anti-inflammatory, immunological, and neurophysiological activities, with low toxicity. Phytochemicals transfer from maternal consumption into breast milk in physiological concentrations, while animal studies demonstrate immunomodulation and other actions of medicinal plants during lactation. Reporting on the use and diverse traditional knowledge of women about plants during the postpartum period is obscured by the marginal place of obstetric issues and by gender biases in ethnobotanical research. In many contemporary contexts use is prejudiced by precautionary risk warnings in health literature and practice that confound lactation with pregnancy. CONCLUSIONS Although systematic investigation of postpartum plant use is lacking, known pharmacological activities support potential benefits on infant development and maternal health with immediate and long-term consequences in relation to allergic, inflammatory, autoimmune, and other diseases. An ethnopharmacological agenda focused on the perinatal period requires directed methodologies and a regional approach in relation to culturally-specific knowledge and practices, traditional plant use, and local health needs. Testing the hypothesis that phytochemicals transferred from medicinal plants into breast milk impact the human immune system and other aspects of infant development requires extended analysis of phytochemicals in human milk and infant lumen and plasma, as well as effects on gastrointestinal and milk microbiome.
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Affiliation(s)
- Lindiwe Sibeko
- Department of Nutrition, School of Public Health and Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Timothy Johns
- School of Human Nutrition, McGill University, Ste. Anne de Bellevue, QC, H9X 3V9, Canada.
| | - Lorraine S Cordeiro
- Department of Nutrition, School of Public Health and Health Sciences, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
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14
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Uy J, Laudicina NM. Assessing the role of the pelvic canal in supporting the gut in humans. PLoS One 2021; 16:e0258341. [PMID: 34634091 PMCID: PMC8504728 DOI: 10.1371/journal.pone.0258341] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 09/25/2021] [Indexed: 11/19/2022] Open
Abstract
The human pelvic canal (true pelvis) functions to support the abdominopelvic organs and serves as a passageway for reproduction (females). Previous research suggests that these two functions work against each other with the expectation that the supportive role results in a narrower pelvic midplane, while fetal passage necessitates a larger opening. In this research, we examine how gut size relates to the size and shape of the true pelvis, which may have implications on how gut size can influence pelvic floor integrity. Pelves and in vivo gut volumes were measured from CT scans of 92 adults (48 female, 44 male). The true pelvis was measured at three obstetrical planes (inlet, midplane, outlet) using 11 3D landmarks. CT volumetry was used to obtain an individual’s gut size. Gut volume was compared to the pelvic planes using multiple regression to evaluate the relationship between gut size and the true pelvis. We find that, in males, larger gut sizes are associated with increased mediolateral canal dimensions at the inlet and midplane. In females, we find that larger gut sizes are associated with more medially-projecting ischial spines and an anteroposteriorly longer outlet. We hypothesize that the association of larger guts with increased canal width in males and increased outlet length in females are adaptations to create adequate space for the gut, while more medially projecting ischial spines reduce the risk of pelvic floor disorders in females, despite its possible spatial consequences for fetal passage.
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Affiliation(s)
- Jeanelle Uy
- Anthropology, California State University Long Beach, Long Beach, California, United States of America
- * E-mail:
| | - Natalie M. Laudicina
- Biomedical Sciences, Grand Valley State University, Allendale, Michigan, United States of America
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15
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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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16
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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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17
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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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18
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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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19
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Biomechanical trade-offs in the pelvic floor constrain the evolution of the human birth canal. Proc Natl Acad Sci U S A 2021; 118:2022159118. [PMID: 33853947 DOI: 10.1073/pnas.2022159118] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Compared with most other primates, humans are characterized by a tight fit between the maternal birth canal and the fetal head, leading to a relatively high risk of neonatal and maternal mortality and morbidities. Obstetric selection is thought to favor a spacious birth canal, whereas the source for opposing selection is frequently assumed to relate to bipedal locomotion. Another, yet underinvestigated, hypothesis is that a more expansive birth canal suspends the soft tissue of the pelvic floor across a larger area, which is disadvantageous for continence and support of the weight of the inner organs and fetus. To test this "pelvic floor hypothesis," we generated a finite element model of the human female pelvic floor and varied its radial size and thickness while keeping all else constant. This allowed us to study the effect of pelvic geometry on pelvic floor deflection (i.e., the amount of bending from the original position) and tissue stresses and stretches. Deflection grew disproportionately fast with increasing radial size, and stresses and stretches also increased. By contrast, an increase in thickness increased pelvic floor stiffness (i.e., the resistance to deformation), which reduced deflection but was unable to fully compensate for the effect of increasing radial size. Moreover, larger thicknesses increase the intra-abdominal pressure necessary for childbirth. Our results support the pelvic floor hypothesis and evince functional trade-offs affecting not only the size of the birth canal but also the thickness and stiffness of the pelvic floor.
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20
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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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21
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Uy J, Hawks J, VanSickle C. Sexual dimorphism of the relationship between the gut and pelvis in humans. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2020; 173:130-140. [PMID: 32519366 DOI: 10.1002/ajpa.24084] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 02/04/2020] [Accepted: 05/06/2020] [Indexed: 01/12/2023]
Abstract
OBJECTIVES Obstetric demands have long been considered in the evolution of the pelvis, yet consideration of the interaction of pregnancy, the pelvis, and the gastrointestinal tract (gut) is lacking. Here, we explore sex differences in the relationship of gut volume with body size and pelvic dimensions. MATERIALS AND METHODS Computed tomography (CT) scans of living adult Homo sapiens (46 females and 42 males) were obtained to measure in vivo gut volume (GV) and to extract 3D models of the pelvis. We collected 19 3D landmarks from each pelvis model to acquire pelvic measurements. We used ordinary least squares regression to explore relationships between GV and body weight, stature, and linear pelvic dimensions. RESULTS The gut-pelvis relationship differs between males and females. Females do not exhibit significant statistical correlations between GV and any variable tested. GV correlates with body size and pelvic outlet size in males. GV scales with negative allometry relative to body weight, stature, maximum bi-iliac breadth, inferior transverse outlet breadth, and bispinous distance in males. DISCUSSION The lack of association between GV and body size in females may be due to limits imposed by the anticipation of accommodating a gravid uterus and/or the increased plasticity of the pelvis. The pattern of relationship between GV and the pelvic outlet suggests the role of the bony pelvis in supporting the adominal viscera in females may be small relative to its role in childbirth. We conclude that gut size inference in fossil hominins from skeletal proxies is limited and confounded by sexual dimorphism.
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Affiliation(s)
- Jeanelle Uy
- Department of Anthropology, California State University, Long Beach, California, USA
| | - John Hawks
- Department of Anthropology, University of Wisconsin-Madison, Madison, Wisconsin, USA.,Evolutionary Studies Institute, University of the Witwatersrand, Private Bag 3, Johannesburg, South Africa
| | - Caroline VanSickle
- Department of Anatomy, A.T. Still University Kirksville College of Osteopathic Medicine, 800 W. Jefferson St., Kirksville, Missouri, USA
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22
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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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23
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Roseman CC, Capellini TD, Jagoda E, Williams SA, Grabowski M, O'Connor C, Polk JD, Cheverud JM. Variation in mouse pelvic morphology maps to locations enriched in Sox9 Class II and Pitx1 regulatory features. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2020; 334:100-112. [PMID: 32017444 DOI: 10.1002/jez.b.22926] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 11/12/2019] [Accepted: 12/21/2019] [Indexed: 11/10/2022]
Abstract
Variation in pelvic morphology has a complex genetic basis and its patterning and specification is governed by conserved developmental pathways. Whether the mechanisms underlying the differentiation and specification of the pelvis also produce the morphological covariation on which natural selection may act, is still an open question in evolutionary developmental biology. We use high-resolution quantitative trait locus (QTL) mapping in the F34 generation of an advanced intercross experiment (LG,SM-G34 ) to characterize the genetic architecture of the mouse pelvis. We test the prediction that genomic features linked to developmental patterning and differentiation of the hind limb and pelvis and the regulation of chondrogenesis are overrepresented in QTL. We find 31 single QTL trait associations at the genome- or chromosome-wise significance level coalescing to 27 pleiotropic loci. We recover further QTL at a more relaxed significance threshold replicating locations found in a previous experiment in an earlier generation of the same population. QTL were more likely than chance to harbor Pitx1 and Sox9 Class II chromatin immunoprecipitation-seq features active during development of skeletal features. There was weak or no support for the enrichment of seven more categories of developmental features drawn from the literature. Our results suggest that genotypic variation is channeled through a subset of developmental processes involved in the generation of phenotypic variation in the pelvis. This finding indicates that the evolvability of complex traits may be subject to biases not evident from patterns of covariance among morphological features or developmental patterning when either is considered in isolation.
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Affiliation(s)
- Charles C Roseman
- Victor E. Shelford Vivarium, Department of Animal Biology, School of Integrative Biology, University of Illinois, Urbana-Champaign, Illinois
| | - Terence D Capellini
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts
| | - Evelyn Jagoda
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts
| | - Scott A Williams
- Department of Anthropology, Center for the Study of Human Origins, New York University, New York, New York.,New York Consortium in Evolutionary Primatology, New York, New York
| | - Mark Grabowski
- Research Centre in Evolutionary Anthropology and Palaeoecology, Liverpool John Moores University, Liverpool, UK
| | - Christine O'Connor
- Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minnesota.,Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota
| | - John D Polk
- Department of Anthropology, University of Illinois, Urbana-Champaign, Illinois.,Department of Biomedical and Translational Sciences, Carle-Illinois College of Medicine, Urbana, Illinois
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24
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Pavličev M, Romero R, Mitteroecker P. Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma. Am J Obstet Gynecol 2020; 222:3-16. [PMID: 31251927 PMCID: PMC9069416 DOI: 10.1016/j.ajog.2019.06.043] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/17/2019] [Accepted: 06/19/2019] [Indexed: 12/18/2022]
Abstract
Without cesarean delivery, obstructed labor can result in maternal and fetal injuries or even death given a disproportion in size between the fetus and the maternal birth canal. The precise frequency of obstructed labor is difficult to estimate because of the widespread use of cesarean delivery for indications other than proven cephalopelvic disproportion, but it has been estimated that at least 1 million mothers per year are affected by this disorder worldwide. Why is the fit between the fetus and the maternal pelvis so tight? Why did evolution not lead to a greater safety margin, as in other primates? Here we review current research and suggest new hypotheses on the evolution of human childbirth and pelvic morphology. In 1960, Washburn suggested that this obstetrical dilemma arose because the human pelvis is an evolutionary compromise between two functions, bipedal gait and childbirth. However, recent biomechanical and kinematic studies indicate that pelvic width does not considerably affect the efficiency of bipedal gait and thus is unlikely to have constrained the evolution of a wider birth canal. Instead, bipedalism may have primarily constrained the flexibility of the pubic symphysis during pregnancy, which opens much wider in most mammals with large fetuses than in humans. We argue that the birth canal is mainly constrained by the trade-off between 2 pregnancy-related functions: while a narrow pelvis is disadvantageous for childbirth, it offers better support for the weight exerted by the viscera and the large human fetus during the long gestation period. We discuss the implications of this hypothesis for understanding pelvic floor dysfunction. Furthermore, we propose that selection for a narrow pelvis has also acted in males because of the role of pelvic floor musculature in erectile function. Finally, we review the cliff-edge model of obstetric selection to explain why evolution cannot completely eliminate cephalopelvic disproportion. This model also predicts that the regular application of life-saving cesarean delivery has evolutionarily increased rates of cephalopelvic disproportion already. We address how evolutionary models contribute to understanding and decision making in obstetrics and gynecology as well as in devising health care policies.
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Affiliation(s)
- Mihaela Pavličev
- Division of Human Genetics, Cincinnati Children`s Hospital Medical Center, Ann Arbor, MI; Department of Pediatrics, University of Cincinnati College of Medicine, Ann Arbor, MI; Department of Philosophy, University of Cincinnati, Ann Arbor, MI.
| | - Roberto Romero
- Perinatology Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Ann Arbor, MI; Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI; Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI; Center for Molecular Medicine and Genetics, Wayne State University, Detroit, MI; Detroit Medical Center, Detroit, MI; Department of Obstetrics and Gynecology, Florida International University, Miami, Florida
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25
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Rosenberg KR, Veile A. Introduction: The evolutionary and biocultural causes and consequences of rising cesarean birth rates. Am J Hum Biol 2019. [DOI: 10.1002/ajhb.23230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
| | - Amanda Veile
- Department of Anthropology; Purdue University; West Lafayette Indiana USA
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26
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Grunstra NDS, Zachos FE, Herdina AN, Fischer B, Pavličev M, Mitteroecker P. Humans as inverted bats: A comparative approach to the obstetric conundrum. Am J Hum Biol 2019; 31:e23227. [PMID: 30810261 PMCID: PMC6492174 DOI: 10.1002/ajhb.23227] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 01/19/2023] Open
Abstract
OBJECTIVES The narrow human birth canal evolved in response to multiple opposing selective forces on the pelvis. These factors cannot be sufficiently disentangled in humans because of the limited range of relevant variation. Here, we outline a comparative strategy to study the evolution of human childbirth and to test existing hypotheses in primates and other mammals. METHODS We combined a literature review with comparative analyses of neonatal and female body and brain mass, using three existing datasets. We also present images of bony pelves of a diverse sample of taxa. RESULTS Bats, certain non-human primates, seals, and most ungulates, including whales, have much larger relative neonatal masses than humans, and they all differ in their anatomical adaptations for childbirth. Bats, as a group, are particularly interesting in this context as they give birth to the relatively largest neonates, and their pelvis is highly dimorphic: Whereas males have a fused symphysis, a ligament bridges a large pubic gap in females. The resulting strong demands on the widened and vulnerable pelvic floor likely are relaxed by roosting head-down. CONCLUSIONS Parturition has constituted a strong selective force in many non-human placentals. We illustrated how the demands on pelvic morphology resulting from locomotion, pelvic floor stability, childbirth, and perhaps also erectile function in males have been traded off differently in mammals, depending on their locomotion and environment. Exploiting the power of a comparative approach, we present new hypotheses and research directions for resolving the obstetric conundrum in humans.
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Affiliation(s)
- Nicole D. S. Grunstra
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Mammal CollectionNatural History Museum ViennaViennaAustria
| | - Frank E. Zachos
- Mammal CollectionNatural History Museum ViennaViennaAustria
- Department of Integrative ZoologyUniversity of ViennaViennaAustria
| | | | - Barbara Fischer
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
| | - Mihaela Pavličev
- Cincinnati Children's Hospital Medical CenterCincinnatiOhio
- Department of PediatricsUniversity of Cincinnati College of MedicineCincinnatiOhio
- Department of PhilosophyUniversity of CincinnatiCincinnatiOhio
| | - Philipp Mitteroecker
- Department of Theoretical BiologyUniversity of ViennaViennaAustria
- Konrad Lorenz Institute for Evolution and Cognition ResearchKlosterneuburgAustria
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