1
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Constant T, Dobson FS, Habold C, Giroud S. Evolutionary trade-offs in dormancy phenology. eLife 2024; 12:RP89644. [PMID: 38669069 PMCID: PMC11052570 DOI: 10.7554/elife.89644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024] Open
Abstract
Seasonal animal dormancy is widely interpreted as a physiological response for surviving energetic challenges during the harshest times of the year (the physiological constraint hypothesis). However, there are other mutually non-exclusive hypotheses to explain the timing of animal dormancy, that is, entry into and emergence from hibernation (i.e. dormancy phenology). Survival advantages of dormancy that have been proposed are reduced risks of predation and competition (the 'life-history' hypothesis), but comparative tests across animal species are few. Using the phylogenetic comparative method applied to more than 20 hibernating mammalian species, we found support for both hypotheses as explanations for the phenology of dormancy. In accordance with the life-history hypotheses, sex differences in hibernation emergence and immergence were favored by the sex difference in reproductive effort. In addition, physiological constraint may influence the trade-off between survival and reproduction such that low temperatures and precipitation, as well as smaller body mass, influence sex differences in phenology. We also compiled initial evidence that ectotherm dormancy may be (1) less temperature dependent than previously thought and (2) associated with trade-offs consistent with the life-history hypothesis. Thus, dormancy during non-life-threatening periods that are unfavorable for reproduction may be more widespread than previously thought.
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Affiliation(s)
- Théo Constant
- UMR 7178, Centre National de la Recherche Scientifique, Institut Pluridisciplinaire Hubert CURIEN, Université de StrasbourgStrasbourgFrance
| | - F Stephen Dobson
- UMR 7178, Centre National de la Recherche Scientifique, Institut Pluridisciplinaire Hubert CURIEN, Université de StrasbourgStrasbourgFrance
- Department of Biological Sciences, Auburn UniversityAuburnUnited States
| | - Caroline Habold
- UMR 7178, Centre National de la Recherche Scientifique, Institut Pluridisciplinaire Hubert CURIEN, Université de StrasbourgStrasbourgFrance
| | - Sylvain Giroud
- Department of Interdisciplinary Life Sciences, Research Institute of Wildlife Ecology, University of Veterinary Medicine ViennaViennaAustria
- Energetic Lab, Department of Biology, Northern Michigan UniversityMarquetteUnited States
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2
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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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3
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Magielse N, Toro R, Steigauf V, Abbaspour M, Eickhoff SB, Heuer K, Valk SL. Phylogenetic comparative analysis of the cerebello-cerebral system in 34 species highlights primate-general expansion of cerebellar crura I-II. Commun Biol 2023; 6:1188. [PMID: 37993596 PMCID: PMC10665558 DOI: 10.1038/s42003-023-05553-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 11/07/2023] [Indexed: 11/24/2023] Open
Abstract
The reciprocal connections between the cerebellum and the cerebrum have been suggested to simultaneously play a role in brain size increase and to support a broad array of brain functions in primates. The cerebello-cerebral system has undergone marked functionally relevant reorganization. In particular, the lateral cerebellar lobules crura I-II (the ansiform) have been suggested to be expanded in hominoids. Here, we manually segmented 63 cerebella (34 primate species; 9 infraorders) and 30 ansiforms (13 species; 8 infraorders) to understand how their volumes have evolved over the primate lineage. Together, our analyses support proportional cerebellar-cerebral scaling, whereas ansiforms have expanded faster than the cerebellum and cerebrum. We did not find different scaling between strepsirrhines and haplorhines, nor between apes and non-apes. In sum, our study shows primate-general structural reorganization of the ansiform, relative to the cerebello-cerebral system, which is relevant for specialized brain functions in an evolutionary context.
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Grants
- RT and KH are supported by the French Agence Nationale de la Recherche, projects NeuroWebLab (ANR-19-DATA-0025) and DMOBE (ANR-21-CE45-0016). KH received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No101033485 (Individual Fellowship). Last, this work was funded in part by Helmholtz Association’s Initiative and Networking Fund under the Helmholtz International Lab grant agreement InterLabs-0015, and the Canada First Research Excellence Fund (CFREF Competition 2, 2015–2016), awarded to the Healthy Brains, Healthy Lives initiative at McGill University, through the Helmholtz International BigBrain Analytics and Learning Laboratory (HIBALL), including NM, SBE, and SLV.
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Affiliation(s)
- Neville Magielse
- Institute of Neuroscience and Medicine, Brain and Behaviour (INM-7), Research Center Jülich, Wilhelm-Johnen-Straße, 52428, Jülich, Germany.
- Otto Hahn Cognitive Neurogenetics Group, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1A, 04103, Leipzig, Germany.
- Institute of Systems Neuroscience, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstraße 5, 40225, Düsseldorf, Germany.
| | - Roberto Toro
- Institut Pasteur, Unité de Neuroanatomie Appliquée et Théorique, Université Paris Cité, 25 rue du Dr. Roux, 75724, Paris, France
| | - Vanessa Steigauf
- Department of Biology, Northern Michigan University, 1401 Presque Isle Ave, MI, 49855, Marquette, USA
| | - Mahta Abbaspour
- Berlin School of Mind and Brain, Humboldt-Universität zu Berlin, Luisenstraße 56, Haus 1, 10117, Berlin, Germany
- Department of Neurology, Charité - Universitätsmedizin Berlin, Bonhoefferweg 3, 10117, Berlin, Germany
| | - Simon B Eickhoff
- Institute of Neuroscience and Medicine, Brain and Behaviour (INM-7), Research Center Jülich, Wilhelm-Johnen-Straße, 52428, Jülich, Germany
- Institute of Systems Neuroscience, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstraße 5, 40225, Düsseldorf, Germany
| | - Katja Heuer
- Institut Pasteur, Unité de Neuroanatomie Appliquée et Théorique, Université Paris Cité, 25 rue du Dr. Roux, 75724, Paris, France
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1A, 04103, Leipzig, Germany
| | - Sofie L Valk
- Institute of Neuroscience and Medicine, Brain and Behaviour (INM-7), Research Center Jülich, Wilhelm-Johnen-Straße, 52428, Jülich, Germany.
- Otto Hahn Cognitive Neurogenetics Group, Max Planck Institute for Human Cognitive and Brain Sciences, Stephanstraße 1A, 04103, Leipzig, Germany.
- Institute of Systems Neuroscience, Medical Faculty, Heinrich Heine University Düsseldorf, Moorenstraße 5, 40225, Düsseldorf, Germany.
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4
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Dunbar RIM, Shultz S. Four errors and a fallacy: pitfalls for the unwary in comparative brain analyses. Biol Rev Camb Philos Soc 2023; 98:1278-1309. [PMID: 37001905 DOI: 10.1111/brv.12953] [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: 09/09/2022] [Revised: 03/17/2023] [Accepted: 03/17/2023] [Indexed: 04/03/2023]
Abstract
Comparative analyses are the backbone of evolutionary analysis. However, their record in producing a consensus has not always been good. This is especially true of attempts to understand the factors responsible for the evolution of large brains, which have been embroiled in an increasingly polarised debate over the past three decades. We argue that most of these disputes arise from a number of conceptual errors and associated logical fallacies that are the result of a failure to adopt a biological systems-based approach to hypothesis-testing. We identify four principal classes of error: a failure to heed Tinbergen's Four Questions when testing biological hypotheses, misapplying Dobzhansky's Dictum when testing hypotheses of evolutionary adaptation, poorly chosen behavioural proxies for underlying hypotheses, and the use of inappropriate statistical methods. In the interests of progress, we urge a more careful and considered approach to comparative analyses, and the adoption of a broader, rather than a narrower, taxonomic perspective.
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Affiliation(s)
- Robin I M Dunbar
- Department of Experimental Psychology, Anna Watts Building, University of Oxford, Oxford, OX2 6GG, UK
| | - Susanne Shultz
- Department of Earth and Environmental Sciences, Michael Smith Building, University of Manchester, Manchester, M13 9PT, UK
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5
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Kozol RA, Conith AJ, Yuiska A, Cree-Newman A, Tolentino B, Benesh K, Paz A, Lloyd E, Kowalko JE, Keene AC, Albertson C, Duboue ER. A brain-wide analysis maps structural evolution to distinct anatomical module. eLife 2023; 12:e80777. [PMID: 37498318 PMCID: PMC10435234 DOI: 10.7554/elife.80777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/26/2023] [Indexed: 07/28/2023] Open
Abstract
The vertebrate brain is highly conserved topologically, but less is known about neuroanatomical variation between individual brain regions. Neuroanatomical variation at the regional level is hypothesized to provide functional expansion, building upon ancestral anatomy needed for basic functions. Classically, animal models used to study evolution have lacked tools for detailed anatomical analysis that are widely used in zebrafish and mice, presenting a barrier to studying brain evolution at fine scales. In this study, we sought to investigate the evolution of brain anatomy using a single species of fish consisting of divergent surface and cave morphs, that permits functional genetic testing of regional volume and shape across the entire brain. We generated a high-resolution brain atlas for the blind Mexican cavefish Astyanax mexicanus and coupled the atlas with automated computational tools to directly assess variability in brain region shape and volume across all populations. We measured the volume and shape of every grossly defined neuroanatomical region of the brain and assessed correlations between anatomical regions in surface fish, cavefish, and surface × cave F2 hybrids, whose phenotypes span the range of surface to cave. We find that dorsal regions of the brain are contracted, while ventral regions have expanded, with F2 hybrid data providing support for developmental constraint along the dorsal-ventral axis. Furthermore, these dorsal-ventral relationships in anatomical variation show similar patterns for both volume and shape, suggesting that the anatomical evolution captured by these two parameters could be driven by similar developmental mechanisms. Together, these data demonstrate that A. mexicanus is a powerful system for functionally determining basic principles of brain evolution and will permit testing how genes influence early patterning events to drive brain-wide anatomical evolution.
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Affiliation(s)
- Robert A Kozol
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Andrew J Conith
- Department of Biology, University of Massachusetts AmherstAmherstUnited States
| | - Anders Yuiska
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Alexia Cree-Newman
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Bernadeth Tolentino
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Kasey Benesh
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Alexandra Paz
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
| | - Evan Lloyd
- Department of Biology, Texas A&M UniversityCollege StationUnited States
| | - Johanna E Kowalko
- Department of Biological Sciences, Lehigh UniversityBethlehemUnited States
| | - Alex C Keene
- Department of Biology, Texas A&M UniversityCollege StationUnited States
| | - Craig Albertson
- Department of Biology, University of Massachusetts AmherstAmherstUnited States
| | - Erik R Duboue
- Jupiter Life Science Initiative, Florida Atlantic UniversityJupiterUnited States
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6
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Schwartz E, Nenning KH, Heuer K, Jeffery N, Bertrand OC, Toro R, Kasprian G, Prayer D, Langs G. Evolution of cortical geometry and its link to function, behaviour and ecology. Nat Commun 2023; 14:2252. [PMID: 37080952 PMCID: PMC10119184 DOI: 10.1038/s41467-023-37574-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 03/22/2023] [Indexed: 04/22/2023] Open
Abstract
Studies in comparative neuroanatomy and of the fossil record demonstrate the influence of socio-ecological niches on the morphology of the cerebral cortex, but have led to oftentimes conflicting theories about its evolution. Here, we study the relationship between the shape of the cerebral cortex and the topography of its function. We establish a joint geometric representation of the cerebral cortices of ninety species of extant Euarchontoglires, including commonly used experimental model organisms. We show that variability in surface geometry relates to species' ecology and behaviour, independent of overall brain size. Notably, ancestral shape reconstruction of the cortical surface and its change during evolution enables us to trace the evolutionary history of localised cortical expansions, modal segregation of brain function, and their association to behaviour and cognition. We find that individual cortical regions follow different sequences of area increase during evolutionary adaptations to dynamic socio-ecological niches. Anatomical correlates of this sequence of events are still observable in extant species, and relate to their current behaviour and ecology. We decompose the deep evolutionary history of the shape of the human cortical surface into spatially and temporally conscribed components with highly interpretable functional associations, highlighting the importance of considering the evolutionary history of cortical regions when studying their anatomy and function.
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Affiliation(s)
- Ernst Schwartz
- Department of Biomedical Imaging and Image-guided Therapy, Computational Imaging Research Lab, Medical University of Vienna, Vienna, Austria
| | - Karl-Heinz Nenning
- Department of Biomedical Imaging and Image-guided Therapy, Computational Imaging Research Lab, Medical University of Vienna, Vienna, Austria
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute, Orangeburg, NY, USA
| | - Katja Heuer
- Institut Pasteur, Université Paris Cité, Unité de Neuroanatomie Appliquée et Théorique, F-75015, Paris, France
| | - Nathan Jeffery
- Institute of Life Course & Medical Sciences, University of Liverpool, Liverpool, England
| | - Ornella C Bertrand
- Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona Edifici ICTA-ICP, c/ Columnes s/n, Campus de la UAB, 08193 Cerdanyola del Vallès., Barcelona, Spain
- School of GeoSciences, University of Edinburgh, Grant Institute, Edinburgh, Scotland, EH9 3FE, United Kingdom
| | - Roberto Toro
- Institut Pasteur, Université Paris Cité, Unité de Neuroanatomie Appliquée et Théorique, F-75015, Paris, France
| | - Gregor Kasprian
- Department of Biomedical Imaging and Image-guided Therapy, Computational Imaging Research Lab, Medical University of Vienna, Vienna, Austria
| | - Daniela Prayer
- Department of Biomedical Imaging and Image-guided Therapy, Computational Imaging Research Lab, Medical University of Vienna, Vienna, Austria
| | - Georg Langs
- Department of Biomedical Imaging and Image-guided Therapy, Computational Imaging Research Lab, Medical University of Vienna, Vienna, Austria.
- Computer Science and Artificial Intelligence Lab, Massachusetts Institute of Technology, Cambridge, MA, USA.
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7
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Townsend C, Ferraro JV, Habecker H, Flinn MV. Human cooperation and evolutionary transitions in individuality. Philos Trans R Soc Lond B Biol Sci 2023; 378:20210414. [PMID: 36688393 PMCID: PMC9869453 DOI: 10.1098/rstb.2021.0414] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
A major evolutionary transition in individuality involves the formation of a cooperative group and the transformation of that group into an evolutionary entity. Human cooperation shares principles with those of multicellular organisms that have undergone transitions in individuality: division of labour, communication, and fitness interdependence. After the split from the last common ancestor of hominoids, early hominins adapted to an increasingly terrestrial niche for several million years. We posit that new challenges in this niche set in motion a positive feedback loop in selection pressure for cooperation that ratcheted coevolutionary changes in sociality, communication, brains, cognition, kin relations and technology, eventually resulting in egalitarian societies with suppressed competition and rapid cumulative culture. The increasing pace of information innovation and transmission became a key aspect of the evolutionary niche that enabled humans to become formidable cooperators with explosive population growth, the ability to cooperate and compete in groups of millions, and emergent social norms, e.g. private property. Despite considerable fitness interdependence, the rise of private property, in concert with population explosion and socioeconomic inequality, subverts potential transition of human groups into evolutionary entities due to resurgence of latent competition and conflict. This article is part of the theme issue 'Human socio-cultural evolution in light of evolutionary transitions'.
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Affiliation(s)
- Cathryn Townsend
- Department of Anthropology, Baylor University, Waco, TX 76798-7334, USA
| | - Joseph V. Ferraro
- Department of Anthropology, Baylor University, Waco, TX 76798-7334, USA
| | - Heather Habecker
- Department of Psychology and Neuroscience, Baylor University, Waco, TX 76798-7334, USA
| | - Mark V. Flinn
- Department of Anthropology, Baylor University, Waco, TX 76798-7334, USA
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8
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Pestana C, de Sousa AA, Todorov OS, Beaudet A, Benoit J. Evolutionary history of hominin brain size and phylogenetic comparative methods. PROGRESS IN BRAIN RESEARCH 2023; 275:217-232. [PMID: 36841569 DOI: 10.1016/bs.pbr.2022.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
An absolutely and relatively large brain has traditionally been viewed as a distinctive characteristic of the Homo genus, with anatomically modern humans presented at the apex of a long line of progressive increases in encephalization. Many studies continue to focus attention on increasing brain size in the Homo genus, while excluding measures of absolute and relative brain size of more geologically recent, smaller brained, hominins such as Homo floresiensis, and Homo naledi and smaller brained Homo erectus specimens. This review discusses the benefits of using phylogenetic comparative methods to trace the diverse changes in hominin brain evolution and the drawbacks of not doing so.
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Affiliation(s)
- Christopher Pestana
- Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
| | | | - Orlin S Todorov
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia
| | - Amélie Beaudet
- Department of Archaeology, University of Cambridge, Cambridge, United Kingdom; School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa; Institut Català de Paleontologia Miquel Crusafont, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Julien Benoit
- Evolutionary Studies Institute, School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa
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9
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The impact of environmental factors on the evolution of brain size in carnivorans. Commun Biol 2022; 5:998. [PMID: 36130990 PMCID: PMC9492690 DOI: 10.1038/s42003-022-03748-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 07/20/2022] [Indexed: 11/28/2022] Open
Abstract
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans’ evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments. The brain size of carnivores has evolved to balance a trade-off between increased cognitive function and increased metabolic cost.
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10
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Abstract
The reasons why some animals have developed larger brains has long been a subject of debate. Yet, it remains unclear which selective pressures may favour the encephalization and how it may act during evolution at different taxonomic scales. Here we studied the patterns and tempo of brain evolution within the order Carnivora and present large-scale comparative analysis of the effect of ecological, environmental, social, and physiological variables on relative brain size in a sample of 174 extant carnivoran species. We found a complex pattern of brain size change between carnivoran families with differences in both the rate and diversity of encephalization. Our findings suggest that during carnivorans' evolution, a trade-off have occurred between the cognitive advantages of acquiring a relatively large brain allowing to adapt to specific environments, and the metabolic costs of the brain which may constitute a disadvantage when facing the need to colonize new environments.
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11
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Hooper R, Brett B, Thornton A. Problems with using comparative analyses of avian brain size to test hypotheses of cognitive evolution. PLoS One 2022; 17:e0270771. [PMID: 35867640 PMCID: PMC9307164 DOI: 10.1371/journal.pone.0270771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 06/16/2022] [Indexed: 11/30/2022] Open
Abstract
There are multiple hypotheses for the evolution of cognition. The most prominent hypotheses are the Social Intelligence Hypothesis (SIH) and the Ecological Intelligence Hypothesis (EIH), which are often pitted against one another. These hypotheses tend to be tested using broad-scale comparative studies of brain size, where brain size is used as a proxy of cognitive ability, and various social and/or ecological variables are included as predictors. Here, we test how robust conclusions drawn from such analyses may be. First, we investigate variation in brain and body size measurements across >1000 bird species. We demonstrate that there is substantial variation in brain and body size estimates across datasets, indicating that conclusions drawn from comparative brain size models are likely to differ depending on the source of the data. Following this, we subset our data to the Corvides infraorder and interrogate how modelling decisions impact results. We show that model results change substantially depending on variable inclusion, source and classification. Indeed, we could have drawn multiple contradictory conclusions about the principal drivers of brain size evolution. These results reflect concerns from a growing number of researchers that conclusions drawn from comparative brain size studies may not be robust. We suggest that to interrogate hypotheses of cognitive evolution, a fruitful way forward is to focus on testing cognitive performance within and between closely related taxa, with an emphasis on understanding the relationship between informational uncertainty and cognitive evolution.
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Affiliation(s)
- Rebecca Hooper
- University of Exeter, Centre for Ecology and Conservation, College of Life and Environmental Sciences, Penryn Campus, Cornwall, United Kingdom
- University of Exeter, Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, Streatham Campus, Exeter, United Kingdom
- * E-mail: (RH); (AT)
| | - Becky Brett
- University of Exeter, Centre for Ecology and Conservation, College of Life and Environmental Sciences, Penryn Campus, Cornwall, United Kingdom
| | - Alex Thornton
- University of Exeter, Centre for Ecology and Conservation, College of Life and Environmental Sciences, Penryn Campus, Cornwall, United Kingdom
- * E-mail: (RH); (AT)
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12
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Barrett L, Henzi SP, Barton RA. Experts in action: why we need an embodied social brain hypothesis. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200533. [PMID: 34957849 PMCID: PMC8710874 DOI: 10.1098/rstb.2020.0533] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The anthropoid primates are known for their intense sociality and large brain size. The idea that these might be causally related has given rise to a large body of work testing the 'social brain hypothesis'. Here, the emphasis has been placed on the political demands of social life, and the cognitive skills that would enable animals to track the machinations of other minds in metarepresentational ways. It seems to us that this position risks losing touch with the fact that brains primarily evolved to enable the control of action, which in turn leads us to downplay or neglect the importance of the physical body in a material world full of bodies and other objects. As an alternative, we offer a view of primate brain and social evolution that is grounded in the body and action, rather than minds and metarepresentation. This article is part of the theme issue 'Systems neuroscience through the lens of evolutionary theory'.
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Affiliation(s)
- Louise Barrett
- Department of Psychology, University of Lethbridge, Lethbridge, Canada
| | - S. Peter Henzi
- Department of Psychology, University of Lethbridge, Lethbridge, Canada
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13
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Walmsley SF, Morrissey MB. Causation, not collinearity: Identifying sources of bias when modelling the evolution of brain size and other allometric traits. Evol Lett 2021; 6:234-244. [PMID: 35784454 PMCID: PMC9233177 DOI: 10.1002/evl3.258] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2020] [Revised: 09/02/2021] [Accepted: 09/06/2021] [Indexed: 12/03/2022] Open
Abstract
Many biological traits covary with body size, resulting in an allometric relationship. Identifying the evolutionary drivers of these traits is complicated by possible relationships between a candidate selective agent and body size itself, motivating the widespread use of multiple regression analysis. However, the possibility that multiple regression may generate misleading estimates when predictor variables are correlated has recently received much attention. Here, we argue that a primary source of such bias is the failure to account for the complex causal structures underlying brains, bodies, and agents. When brains and bodies are expected to evolve in a correlated manner over and above the effects of specific agents of selection, neither simple nor multiple regression will identify the true causal effect of an agent on brain size. This problem results from the inclusion of a predictor variable in a regression analysis that is (in part) a consequence of the response variable. We demonstrate these biases with examples and derive estimators to identify causal relationships when traits evolve as a function of an existing allometry. Model mis‐specification relative to plausible causal structures, not collinearity, requires further consideration as an important source of bias in comparative analyses.
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Affiliation(s)
- Sam F. Walmsley
- Scottish Oceans Institute, School of Biology, University of St. Andrews East Sands St. Andrews United Kingdom
| | - Michael B. Morrissey
- Dyers Brae House, School of Biology, University of St. Andrews Greenside Pl St. Andrews United Kingdom
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14
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van Schaik CP, Triki Z, Bshary R, Heldstab SA. A Farewell to the Encephalization Quotient: A New Brain Size Measure for Comparative Primate Cognition. BRAIN, BEHAVIOR AND EVOLUTION 2021; 96:1-12. [PMID: 34247154 DOI: 10.1159/000517013] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 05/02/2021] [Indexed: 11/19/2022]
Abstract
Both absolute and relative brain sizes vary greatly among and within the major vertebrate lineages. Scientists have long debated how larger brains in primates and hominins translate into greater cognitive performance, and in particular how to control for the relationship between the noncognitive functions of the brain and body size. One solution to this problem is to establish the slope of cognitive equivalence, i.e., the line connecting organisms with an identical bauplan but different body sizes. The original approach to estimate this slope through intraspecific regressions was abandoned after it became clear that it generated slopes that were too low by an unknown margin due to estimation error. Here, we revisit this method. We control for the error problem by focusing on highly dimorphic primate species with large sample sizes and fitting a line through the mean values for adult females and males. We obtain the best estimate for the slope of circa 0.27, a value much lower than those constructed using all mammal species and close to the value expected based on the genetic correlation between brain size and body size. We also find that the estimate of cognitive brain size based on cognitive equivalence fits empirical cognitive studies better than the encephalization quotient, which should therefore be avoided in future studies on primates and presumably mammals and birds in general. The use of residuals from the line of cognitive equivalence may change conclusions concerning the cognitive abilities of extant and extinct primate species, including hominins.
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Affiliation(s)
- Carel P van Schaik
- Department of Anthropology and Anthropological Museum, University of Zurich, Zurich, Switzerland.,Department of Evolutionary Biology and Environmental Science, University of Zurich, Zurich, Switzerland
| | - Zegni Triki
- Behavioral Ecology Laboratory, Faculty of Science, University of Neuchâtel, Neuchâtel, Switzerland, .,Institute of Zoology, Stockholm University, Stockholm, Sweden,
| | - Redouan Bshary
- Behavioral Ecology Laboratory, Faculty of Science, University of Neuchâtel, Neuchâtel, Switzerland
| | - Sandra A Heldstab
- Department of Anthropology and Anthropological Museum, University of Zurich, Zurich, Switzerland
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15
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Lindenfors P, Wartel A, Lind J. 'Dunbar's number' deconstructed. Biol Lett 2021; 17:20210158. [PMID: 33947220 PMCID: PMC8103230 DOI: 10.1098/rsbl.2021.0158] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 04/14/2021] [Indexed: 12/14/2022] Open
Abstract
A widespread and popular belief posits that humans possess a cognitive capacity that is limited to keeping track of and maintaining stable relationships with approximately 150 people. This influential number, 'Dunbar's number', originates from an extrapolation of a regression line describing the relationship between relative neocortex size and group size in primates. Here, we test if there is statistical support for this idea. Our analyses on complementary datasets using different methods yield wildly different numbers. Bayesian and generalized least-squares phylogenetic methods generate approximations of average group sizes between 69-109 and 16-42, respectively. However, enormous 95% confidence intervals (4-520 and 2-336, respectively) imply that specifying any one number is futile. A cognitive limit on human group size cannot be derived in this manner.
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Affiliation(s)
- Patrik Lindenfors
- Institute for Futures Studies, Box 591, 101 31 Stockholm, Sweden
- Centre for Cultural Evolution, Stockholm University, Sweden
| | - Andreas Wartel
- Centre for Cultural Evolution, Stockholm University, Sweden
| | - Johan Lind
- Centre for Cultural Evolution, Stockholm University, Sweden
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16
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Todorov OS, Blomberg SP, Goswami A, Sears K, Drhlík P, Peters J, Weisbecker V. Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework. Proc Biol Sci 2021; 288:20210394. [PMID: 33784860 PMCID: PMC8059968 DOI: 10.1098/rspb.2021.0394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Considerable controversy exists about which hypotheses and variables best explain mammalian brain size variation. We use a new, high-coverage dataset of marsupial brain and body sizes, and the first phylogenetically imputed full datasets of 16 predictor variables, to model the prevalent hypotheses explaining brain size evolution using phylogenetically corrected Bayesian generalized linear mixed-effects modelling. Despite this comprehensive analysis, litter size emerges as the only significant predictor. Marsupials differ from the more frequently studied placentals in displaying a much lower diversity of reproductive traits, which are known to interact extensively with many behavioural and ecological predictors of brain size. Our results therefore suggest that studies of relative brain size evolution in placental mammals may require targeted co-analysis or adjustment of reproductive parameters like litter size, weaning age or gestation length. This supports suggestions that significant associations between behavioural or ecological variables with relative brain size may be due to a confounding influence of the extensive reproductive diversity of placental mammals.
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Affiliation(s)
- Orlin S Todorov
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Simone P Blomberg
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia
| | - Anjali Goswami
- Genetics, Evolution, and Environment Department, University College London, UK.,Department of Life Sciences, Natural History Museum, London, UK
| | - Karen Sears
- Department of Ecology and Evolutionary Biology, College of Life Sciences, University of California Los Angeles, CA, USA
| | - Patrik Drhlík
- Faculty of Mechatronics, Informatics and Interdisciplinary Studies, Technical University of Liberec, Czechia
| | - James Peters
- Department of Animal Biology, University of Illinois at Urbana Champaign, USA
| | - Vera Weisbecker
- School of Biological Sciences, The University of Queensland, St Lucia, Queensland, Australia.,College of Science and Engineering, Flinders University, Australia
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17
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Muratore IB, Traniello JFA. Fungus-Growing Ants: Models for the Integrative Analysis of Cognition and Brain Evolution. Front Behav Neurosci 2020; 14:599234. [PMID: 33424560 PMCID: PMC7793780 DOI: 10.3389/fnbeh.2020.599234] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2020] [Accepted: 11/23/2020] [Indexed: 11/26/2022] Open
Affiliation(s)
| | - James F. A. Traniello
- Department of Biology, Boston University, Boston, MA, United States
- Graduate Program in Neuroscience, Boston University, Boston, MA, United States
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