151
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Montgomery SH. The relationship between play, brain growth and behavioural flexibility in primates. Anim Behav 2014. [DOI: 10.1016/j.anbehav.2014.02.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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152
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Symonds MRE, Weston MA, Robinson RW, Guay PJ. Comparative analysis of classic brain component sizes in relation to flightiness in birds. PLoS One 2014; 9:e91960. [PMID: 24637884 PMCID: PMC3956822 DOI: 10.1371/journal.pone.0091960] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Accepted: 02/17/2014] [Indexed: 11/19/2022] Open
Abstract
Increased encephalization has been linked to a range of behavioural traits and scenarios. However, studies of whole brain size in this context have been criticised for ignoring the role of specific brain areas in controlling behaviour. In birds, the response to potential threats is one such behaviour that may relate to the way in which the brain processes sensory information. We used a phylogenetic generalised least squares (PGLS) analyses, based on five different phylogenetic hypotheses, to analyse the relationship of relative sizes of whole brain and brain components with Flight-Initiation Distance (FID), the distance at which birds flee from an approaching human, for 41 bird species. Starting distance (the distance at which an approach to a bird commences), body mass and eye size have elsewhere been shown to be positively associated with FID, and consequently were included as covariates in our analysis. Starting distance and body mass were by far the strongest predictors of FID. Of all brain components, cerebellum size had the strongest predictor weight and was negatively associated with FID but the confidence intervals on the average estimate included zero and the overall predictor weight was low. Models featuring individual brain components were generally more strongly weighted than models featuring whole brain size. The PGLS analyses estimated there to be no phylogenetic signal in the regression models, and hence produced results equivalent to ordinary least squares regression analysis. However analyses that assumed strong phylogenetic signal produced substantially different results with each phylogeny, and overall suggest a negative relationship between forebrain size and FID. Our analyses suggest that the evolutionary assumptions of the comparative analysis, and consideration of starting distance make a profound difference to the interpretation of the effect of brain components on FID in birds.
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Affiliation(s)
- Matthew R. E. Symonds
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria, Australia
- * E-mail:
| | - Michael A. Weston
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria, Australia
| | - Randall W. Robinson
- Applied Ecology Research Group & Institute for Sustainability and Innovation, College of Engineering and Science, Victoria University, St. Albans, Victoria, Australia
| | - Patrick-Jean Guay
- Applied Ecology Research Group & Institute for Sustainability and Innovation, College of Engineering and Science, Victoria University, St. Albans, Victoria, Australia
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154
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Kotrschal A, Lievens EJP, Dahlbom J, Bundsen A, Semenova S, Sundvik M, Maklakov AA, Winberg S, Panula P, Kolm N. Artificial selection on relative brain size reveals a positive genetic correlation between brain size and proactive personality in the guppy. Evolution 2014; 68:1139-49. [PMID: 24359469 PMCID: PMC4285157 DOI: 10.1111/evo.12341] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 12/09/2013] [Indexed: 01/22/2023]
Abstract
Animal personalities range from individuals that are shy, cautious, and easily stressed (a “reactive” personality type) to individuals that are bold, innovative, and quick to learn novel tasks, but also prone to routine formation (a “proactive” personality type). Although personality differences should have important consequences for fitness, their underlying mechanisms remain poorly understood. Here, we investigated how genetic variation in brain size affects personality. We put selection lines of large- and small-brained guppies (Poecilia reticulata), with known differences in cognitive ability, through three standard personality assays. First, we found that large-brained animals were faster to habituate to, and more exploratory in, open field tests. Large-brained females were also bolder. Second, large-brained animals excreted less cortisol in a stressful situation (confinement). Third, large-brained animals were slower to feed from a novel food source, which we interpret as being caused by reduced behavioral flexibility rather than lack of innovation in the large-brained lines. Overall, the results point toward a more proactive personality type in large-brained animals. Thus, this study provides the first experimental evidence linking brain size and personality, an interaction that may affect important fitness-related aspects of ecology such as dispersal and niche exploration.
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Affiliation(s)
- Alexander Kotrschal
- Department for Integrative Biology and Evolution (KLIVV), Veterinary University Vienna, Savoyenstrasse 1A, 1160 Vienna, Austria; Department of Ecology & Genetics/Animal Ecology, Uppsala University, Norbyvägen 18D, SE-75236 Uppsala, Sweden.
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Moczek AP, Kijimoto T, Snell-Rood E, Rocha G, Pespeni M, Kafadar K. Evolutionary and Ecological Genomics of Developmental Plasticity: Novel Approaches and First Insights From the Study of Horned Beetles. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 781:127-48. [DOI: 10.1007/978-94-007-7347-9_7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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156
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Montgomery SH. Primate brains, the ‘island rule’ and the evolution of Homo floresiensis. J Hum Evol 2013; 65:750-60. [DOI: 10.1016/j.jhevol.2013.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 08/21/2013] [Accepted: 08/26/2013] [Indexed: 10/26/2022]
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157
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Performance in cognitive and problem-solving tasks in male spotted bowerbirds does not correlate with mating success. Anim Behav 2013. [DOI: 10.1016/j.anbehav.2013.07.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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158
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Lendvai ÁZ, Bókony V, Angelier F, Chastel O, Sol D. Do smart birds stress less? An interspecific relationship between brain size and corticosterone levels. Proc Biol Sci 2013; 280:20131734. [PMID: 24026820 DOI: 10.1098/rspb.2013.1734] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Vertebrates respond to unpredictable noxious environmental stimuli by increasing secretion of glucocorticoids (CORT). Although this hormonal stress response is adaptive, high levels of CORT may induce significant costs if stressful situations are frequent. Thus, alternative coping mechanisms that help buffer individuals against environmental stressors may be selected for when the costs of CORT levels are elevated. By allowing individuals to identify, anticipate and cope with the stressful circumstances, cognition may enable stress-specific behavioural coping. Although there is evidence that behavioural responses allow animals to cope with stressful situations, it is unclear whether or not cognition reduces investment in the neuroendocrine stress response. Here, we report that in birds, species with larger brains relative to their body size show lower baseline and peak CORT levels than species with smaller brains. This relationship is consistent across life-history stages, and cannot be accounted for by differences in life history and geographical latitude. Because a large brain is a major feature of birds that base their lifetime in learning new things, our results support the hypothesis that enhanced cognition represents a general alternative to the neuroendocrine stress response.
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Affiliation(s)
- Ádám Z Lendvai
- Department of Biology, Virginia Tech, , 4102 Derring Hall, Blacksburg, VA, USA, Department of Biology, College of Nyíregyháza, , Sóstói út 31/b, Nyíregyháza, Hungary, Department of Limnology, University of Pannonia, , Pf. 158, 8201 Veszprém, Hungary, Centre d'Études Biologiques de Chizé, Centre National de la Recherche Scientifique, , Villiers-en-Bois, 79360 Beauvoir sur Niort, France, CREAF, , Sciences Building, Cerdanyola del Vallès 08193, Spain, CSIC, , Cerdanyola del Vallès 08193, Spain
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159
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Nettle D, Dickins TE, Coall DA, de Mornay Davies P. Patterns of physical and psychological development in future teenage mothers. EVOLUTION MEDICINE AND PUBLIC HEALTH 2013; 2013:187-96. [PMID: 24481198 PMCID: PMC3868355 DOI: 10.1093/emph/eot016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The developmental patterns of teenage mothers are consistent with the idea that early childbearing is a component of an accelerated reproductive strategy induced by early-life conditions. The implications for interventions likely to affect the rate of teenage childbearing are discussed. Background and objectives: Teenage childbearing may have childhood origins and can be viewed as the outcome of a coherent reproductive strategy associated with early environmental conditions. Life-history theory would predict that where futures are uncertain fitness can be maximized through diverting effort from somatic development into reproduction. Even before the childbearing years, future teenage mothers differ from their peers both physically and psychologically, indicating early calibration to key ecological factors. Cohort data have not been deliberately collected to test life-history hypotheses within Western populations. Nonetheless, existing data sets can be used to pursue relevant patterns using socioeconomic variables as indices of relevant ecologies. Methodology: We examined the physical and psychological development of 599 young women from the National Child Development Study who became mothers before age 20, compared to 599 socioeconomically matched controls. Results: Future young mothers were lighter than controls at birth and shorter at age 7. They had earlier menarche and accelerated breast development, earlier cessation of growth and shorter adult stature. Future young mothers had poorer emotional and behavioural adjustment than controls at age 7 and especially 11, and by age 16, idealized younger ages for marriage and parenthood than did the controls. Conclusions and implications: The developmental patterns we observed are consistent with the idea that early childbearing is a component of an accelerated reproductive strategy that is induced by early-life conditions. We discuss the implications for the kinds of interventions likely to affect the rate of teenage childbearing.
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Affiliation(s)
- Daniel Nettle
- Centre for Behaviour and Evolution, Institute of Neuroscience, Newcastle University, Newcastle, UK; Department of Psychology, Middlesex University, London, UK; Community, Culture, and Mental Health Unit, School of Psychiatry and Clinical Neurosciences, University of Western Australia, Crawley, Australia; and School of Medical Sciences, Edith Cowan University, Joondalup, Australia
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160
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Onyango PO, Gesquiere LR, Altmann J, Alberts SC. Puberty and dispersal in a wild primate population. Horm Behav 2013; 64:240-9. [PMID: 23998668 PMCID: PMC3764504 DOI: 10.1016/j.yhbeh.2013.02.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 12/31/2012] [Accepted: 02/16/2013] [Indexed: 11/25/2022]
Abstract
This article is part of a Special Issue "Puberty and Adolescence". The onset of reproduction is preceded by a host of organismal adjustments and transformations, involving morphological, physiological, and behavioral changes. In highly social mammals, including humans and most nonhuman primates, the timing and nature of maturational processes are affected by the animal's social milieu as well as its ecology. Here, we review a diverse set of findings on how maturation unfolds in wild baboons in the Amboseli basin of southern Kenya, and we place these findings in the context of other reports of maturational processes in primates and other mammals. First, we describe the series of events and processes that signal maturation in female and male baboons. Sex differences in age at both sexual maturity and first reproduction documented for this species are consistent with expectations of life history theory; males mature later than females and exhibit an adolescent growth spurt that is absent or minimal in females. Second, we summarize what we know about sources of variance in the timing of maturational processes including natal dispersal. In Amboseli, individuals in a food-enhanced group mature earlier than their wild-feeding counterparts, and offspring of high-ranking females mature earlier than offspring of low-ranking females. We also report on how genetic admixture, which occurs in Amboseli between two closely related baboon taxa, affects individual maturation schedules.
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161
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Willemet R. Reconsidering the evolution of brain, cognition, and behavior in birds and mammals. Front Psychol 2013; 4:396. [PMID: 23847570 PMCID: PMC3696912 DOI: 10.3389/fpsyg.2013.00396] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 06/12/2013] [Indexed: 01/23/2023] Open
Abstract
Despite decades of research, some of the most basic issues concerning the extraordinarily complex brains and behavior of birds and mammals, such as the factors responsible for the diversity of brain size and composition, are still unclear. This is partly due to a number of conceptual and methodological issues. Determining species and group differences in brain composition requires accounting for the presence of taxon-cerebrotypes and the use of precise statistical methods. The role of allometry in determining brain variables should be revised. In particular, bird and mammalian brains appear to have evolved in response to a variety of selective pressures influencing both brain size and composition. “Brain” and “cognition” are indeed meta-variables, made up of the variables that are ecologically relevant and evolutionarily selected. External indicators of species differences in cognition and behavior are limited by the complexity of these differences. Indeed, behavioral differences between species and individuals are caused by cognitive and affective components. Although intra-species variability forms the basis of species evolution, some of the mechanisms underlying individual differences in brain and behavior appear to differ from those between species. While many issues have persisted over the years because of a lack of appropriate data or methods to test them; several fallacies, particularly those related to the human brain, reflect scientists' preconceptions. The theoretical framework on the evolution of brain, cognition, and behavior in birds and mammals should be reconsidered with these biases in mind.
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162
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163
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Mery F. Natural variation in learning and memory. Curr Opin Neurobiol 2013; 23:52-6. [DOI: 10.1016/j.conb.2012.09.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Revised: 08/31/2012] [Accepted: 09/09/2012] [Indexed: 12/14/2022]
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164
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Kotrschal A, Rogell B, Bundsen A, Svensson B, Zajitschek S, Brännström I, Immler S, Maklakov A, Kolm N. Artificial selection on relative brain size in the guppy reveals costs and benefits of evolving a larger brain. Curr Biol 2013; 23:168-71. [PMID: 23290552 PMCID: PMC3566478 DOI: 10.1016/j.cub.2012.11.058] [Citation(s) in RCA: 307] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 11/09/2012] [Accepted: 11/29/2012] [Indexed: 11/19/2022]
Abstract
The large variation in brain size that exists in the animal kingdom has been suggested to have evolved through the balance between selective advantages of greater cognitive ability and the prohibitively high energy demands of a larger brain (the “expensive-tissue hypothesis” [1]). Despite over a century of research on the evolution of brain size, empirical support for the trade-off between cognitive ability and energetic costs is based exclusively on correlative evidence [2], and the theory remains controversial [3, 4]. Here we provide experimental evidence for costs and benefits of increased brain size. We used artificial selection for large and small brain size relative to body size in a live-bearing fish, the guppy (Poecilia reticulata), and found that relative brain size evolved rapidly in response to divergent selection in both sexes. Large-brained females outperformed small-brained females in a numerical learning assay designed to test cognitive ability. Moreover, large-brained lines, especially males, developed smaller guts, as predicted by the expensive-tissue hypothesis [1], and produced fewer offspring. We propose that the evolution of brain size is mediated by a functional trade-off between increased cognitive ability and reproductive performance and discuss the implications of these findings for vertebrate brain evolution.
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Affiliation(s)
- Alexander Kotrschal
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Björn Rogell
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Andreas Bundsen
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Beatrice Svensson
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Susanne Zajitschek
- Evolutionary Biology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Ioana Brännström
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Simone Immler
- Evolutionary Biology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Alexei A. Maklakov
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Niclas Kolm
- Animal Ecology, Department of Ecology and Genetics, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
- Corresponding author
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165
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Lefebvre L, Reader SM, Sol D. Innovating Innovation Rate and Its Relationship with Brains, Ecology and General Intelligence. BRAIN, BEHAVIOR AND EVOLUTION 2013; 81:143-5. [DOI: 10.1159/000348485] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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166
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167
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168
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Abstract
Much attention has focused on the dramatic expansion of the forebrain, particularly the neocortex, as the neural substrate of cognitive evolution. However, though relatively small, the cerebellum contains about four times more neurons than the neocortex. I show that commonly used comparative measures such as neocortex ratio underestimate the contribution of the cerebellum to brain evolution. Once differences in the scaling of connectivity in neocortex and cerebellum are accounted for, a marked and general pattern of correlated evolution of the two structures is apparent. One deviation from this general pattern is a relative expansion of the cerebellum in apes and other extractive foragers. The confluence of these comparative patterns, studies of ape foraging skills and social learning, and recent evidence on the cognitive neuroscience of the cerebellum, suggest an important role for the cerebellum in the evolution of the capacity for planning, execution and understanding of complex behavioural sequences--including tool use and language. There is no clear separation between sensory-motor and cognitive specializations underpinning such skills, undermining the notion of executive control as a distinct process. Instead, I argue that cognitive evolution is most effectively understood as the elaboration of specialized systems for embodied adaptive control.
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Affiliation(s)
- Robert A Barton
- Evolutionary Anthropology Research Group, Department of Anthropology, Durham University, Dawson Building, South Road, Durham DH1 3LE, UK.
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169
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GUAY PJ, WESTON MA, SYMONDS MRE, GLOVER HK. Brains and bravery: Little evidence of a relationship between brain size and flightiness in shorebirds. AUSTRAL ECOL 2012. [DOI: 10.1111/j.1442-9993.2012.02441.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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170
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Sol D, Maspons J, Vall-Llosera M, Bartomeus I, García-Peña GE, Piñol J, Freckleton RP. Unraveling the Life History of Successful Invaders. Science 2012; 337:580-3. [PMID: 22859488 DOI: 10.1126/science.1221523] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Daniel Sol
- Center for Ecological Research and Forestry Applications, 08193 Cerdanyola del Vallès, Spain.
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171
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van Schaik CP, Isler K, Burkart JM. Explaining brain size variation: from social to cultural brain. Trends Cogn Sci 2012; 16:277-84. [DOI: 10.1016/j.tics.2012.04.004] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 04/03/2012] [Accepted: 04/05/2012] [Indexed: 11/30/2022]
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172
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Nicotinamide, NAD(P)(H), and Methyl-Group Homeostasis Evolved and Became a Determinant of Ageing Diseases: Hypotheses and Lessons from Pellagra. Curr Gerontol Geriatr Res 2012; 2012:302875. [PMID: 22536229 PMCID: PMC3318212 DOI: 10.1155/2012/302875] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 12/19/2011] [Indexed: 01/22/2023] Open
Abstract
Compartmentalized redox faults are common to ageing diseases. Dietary constituents are catabolized to NAD(H) donating electrons producing proton-based bioenergy in coevolved, cross-species and cross-organ networks. Nicotinamide and NAD deficiency from poor diet or high expenditure causes pellagra, an ageing and dementing disorder with lost robustness to infection and stress. Nicotinamide and stress induce Nicotinamide-N-methyltransferase (NNMT) improving choline retention but consume methyl groups. High NNMT activity is linked to Parkinson's, cancers, and diseases of affluence. Optimising nicotinamide and choline/methyl group availability is important for brain development and increased during our evolution raising metabolic and methylome ceilings through dietary/metabolic symbiotic means but strict energy constraints remain and life-history tradeoffs are the rule. An optimal energy, NAD and methyl group supply, avoiding hypo and hyper-vitaminoses nicotinamide and choline, is important to healthy ageing and avoids utilising double-edged symbionts or uncontrolled autophagy or reversions to fermentation reactions in inflammatory and cancerous tissue that all redistribute NAD(P)(H), but incur high allostatic costs.
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173
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Energetics and the evolution of human brain size. Nature 2011; 480:91-3. [DOI: 10.1038/nature10629] [Citation(s) in RCA: 329] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2011] [Accepted: 10/12/2011] [Indexed: 11/08/2022]
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174
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van Woerden JT, Willems EP, van Schaik CP, Isler K. LARGE BRAINS BUFFER ENERGETIC EFFECTS OF SEASONAL HABITATS IN CATARRHINE PRIMATES. Evolution 2011; 66:191-9. [DOI: 10.1111/j.1558-5646.2011.01434.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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175
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Speciation, diversity, and Mode 1 technologies: The impact of variability selection. J Hum Evol 2011; 61:306-19. [DOI: 10.1016/j.jhevol.2011.04.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 04/03/2011] [Accepted: 04/10/2011] [Indexed: 11/20/2022]
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176
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Sobrero R, May-Collado LJ, Agnarsson I, Hernández CE. Expensive Brains: "Brainy" Rodents have Higher Metabolic Rate. FRONTIERS IN EVOLUTIONARY NEUROSCIENCE 2011; 3:2. [PMID: 21811456 PMCID: PMC3141350 DOI: 10.3389/fnevo.2011.00002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 06/15/2011] [Indexed: 12/03/2022]
Abstract
Brains are the centers of the nervous system of animals, controlling the organ systems of the body and coordinating responses to changes in the ecological and social environment. The evolution of traits that correlate with cognitive ability, such as relative brain size is thus of broad interest. Brain mass relative to body mass (BM) varies among mammals, and diverse factors have been proposed to explain this variation. A recent study provided evidence that energetics play an important role in brain evolution (Isler and van Schaik, 2006). Using composite phylogenies and data drawn from multiple sources, these authors showed that basal metabolic rate (BMR) correlates with brain mass across mammals. However, no such relationship was found within rodents. Here we re-examined the relationship between BMR and brain mass within Rodentia using a novel species-level phylogeny. Our results are sensitive to parameter evaluation; in particular how species mass is estimated. We detect no pattern when applying an approach used by previous studies, where each species BM is represented by two different numbers, one being the individual that happened to be used for BMR estimates of that species. However, this approach may compromise the analysis. When using a single value of BM for each species, whether representing a single individual, or available species mean, our findings provide evidence that brain mass (independent of BM) and BMR are correlated. These findings are thus consistent with the hypothesis that large brains evolve when the payoff for increased brain mass is greater than the energetic cost they incur.
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Affiliation(s)
- Raúl Sobrero
- Departamento de Ecología, Pontificia Universidad Católica de ChileSantiago, Chile
| | - Laura J. May-Collado
- Department of Environmental Science and Policy, George Mason UniversityFairfax, VA, USA
- Department of Biology, University of Puerto RicoSan Juan, PR, USA
| | - Ingi Agnarsson
- Department of Biology, University of Puerto RicoSan Juan, PR, USA
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177
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Maternal investment, life histories, and the costs of brain growth in mammals. Proc Natl Acad Sci U S A 2011; 108:6169-74. [PMID: 21444808 DOI: 10.1073/pnas.1019140108] [Citation(s) in RCA: 125] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Brain size variation in mammals correlates with life histories: larger-brained species have longer gestations, mature later, and have increased lifespans. These patterns have been explained in terms of developmental costs (larger brains take longer to grow) and cognitive benefits (large brains enhance survival and increase lifespan). In support of the developmental cost hypothesis, we show that evolutionary changes in pre- and postnatal brain growth correlate specifically with duration of the relevant phases of maternal investment (gestation and lactation, respectively). We also find support for the hypothesis that the rate of fetal brain growth is related to the energy turnover of the mother. In contrast, we find no support for hypotheses proposing that costs are accommodated through direct tradeoffs between brain and body growth, or between brain growth and litter size. When the duration of maternal investment is taken into account, adult brain size is uncorrelated with other life history traits such as lifespan. Hence, the general pattern of slower life histories in large-brained species appears to be a direct consequence of developmental costs.
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178
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Finarelli JA. Estimating endocranial volume from the outside of the skull in Artiodactyla. J Mammal 2011. [DOI: 10.1644/09-mamm-a-391.1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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179
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Weisbecker V, Goswami A. Neonatal maturity as the key to understanding brain size evolution in homeothermic vertebrates. Bioessays 2010; 33:155-8. [PMID: 21319183 DOI: 10.1002/bies.201000128] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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180
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Abstract
Many mammals have brains substantially larger than expected for their body size, but the reasons for this remain ambiguous. Enlarged brains are metabolically expensive and require elongated developmental periods, and so natural selection should have favoured their evolution only if they provide counterbalancing advantages. One possible advantage is facilitating the construction of behavioural responses to unusual, novel or complex socio-ecological challenges. This buffer effect should increase survival rates and favour a longer reproductive life, thereby compensating for the costs of delayed reproduction. Here, using a global database of 493 species, we provide evidence showing that mammals with enlarged brains (relative to their body size) live longer and have a longer reproductive lifespan. Our analysis supports and extends previous findings, accounting for the possible confounding effects of other life history traits, ecological and dietary factors, and phylogenetic autocorrelation. Thus, these findings provide support for the hypothesis that mammals counterbalance the costs of affording large brains with a longer reproductive life.
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Affiliation(s)
- C González-Lagos
- CREAF (Centre for Ecological Research and Applied Forestries), Autonomous University of Barcelona, Bellaterra, Catalonia, Spain.
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181
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Abstract
Attempts to relate brain size to behaviour and cognition have rarely integrated information from insects with that from vertebrates. Many insects, however, demonstrate that highly differentiated motor repertoires, extensive social structures and cognition are possible with very small brains, emphasising that we need to understand the neural circuits, not just the size of brain regions, which underlie these feats. Neural network analyses show that cognitive features found in insects, such as numerosity, attention and categorisation-like processes, may require only very limited neuron numbers. Thus, brain size may have less of a relationship with behavioural repertoire and cognitive capacity than generally assumed, prompting the question of what large brains are for. Larger brains are, at least partly, a consequence of larger neurons that are necessary in large animals due to basic biophysical constraints. They also contain greater replication of neuronal circuits, adding precision to sensory processes, detail to perception, more parallel processing and enlarged storage capacity. Yet, these advantages are unlikely to produce the qualitative shifts in behaviour that are often assumed to accompany increased brain size. Instead, modularity and interconnectivity may be more important.
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183
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Affiliation(s)
- Tom V Smulders
- Centre for Behaviour and Evolution, Institute of Neuroscience, University of Newcastle, Newcastle NE2 4HH, UK.
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