scholarly journals Metabolic costs of brain size evolution

2006 ◽  
Vol 2 (4) ◽  
pp. 557-560 ◽  
Author(s):  
Karin Isler ◽  
Carel P van Schaik
Keyword(s):  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Energy Costs ◽  
Main Interest ◽  
Ecological Benefits ◽  
Size Evolution ◽  
Large Brain ◽  
Metabolic Costs ◽  
Cognitive Benefits

Abstract In the ongoing discussion about brain evolution in vertebrates, the main interest has shifted from theories focusing on energy balance to theories proposing social or ecological benefits of enhanced intellect. With the availability of a wealth of new data on basal metabolic rate (BMR) and brain size and with the aid of reliable techniques of comparative analysis, we are able to show that in fact energetics is an issue in the maintenance of a relatively large brain, and that brain size is positively correlated with the BMR in mammals, controlling for body size effects. We conclude that attempts to explain brain size variation in different taxa must consider the ability to sustain the energy costs alongside cognitive benefits.

Brain size in Hylarana guentheri seems unaffected by variation in temperature and growth season

2017 ◽  
Vol 67 (3-4) ◽  
pp. 209-225 ◽  
Author(s):  
Jun Gu ◽  
Da Yong Li ◽  
Yi Luo ◽  
Song Bei Ying ◽  
Lan Ya Zhang ◽  
...  
Keyword(s):  
Brain Size ◽  
Behavioral Flexibility ◽  
Size Variation ◽  
Brain Regions ◽  
Growth Season ◽  
Food Scarcity ◽  
Size Evolution ◽  
Cognitive Benefits ◽  
Males And Females ◽  
Temperature And Growth

Brain size varies dramatically between vertebrate species. Two prominent adaptive hypotheses – the Cognitive Buffer Hypothesis (CBH) and the Expensive Brain Hypothesis (EBH) – have been proposed to explain brain size evolution. The CBH assumes that brain size should increase with seasonality, as the cognitive benefits of a larger brain should help overcoming periods of food scarcity via, for example, increased behavioral flexibility. Alternatively, the EBH states that brain size should decrease with seasonality because a smaller brain confers energetic benefits in periods of food scarcity. Here, to test the two adaptive hypotheses by studying the effects of variation in temperature and growth season on variations in overall brain size and the size of specific brain regions (viz. olfactory nerves, olfactory bulbs, telencephalon, optic tectum and cerebellum) among Hylarana guentheri populations. Inconsistent with the predictions of both the EBH and the CBH, variation in temperature and growth season did not exhibit correlations with overall brain size and the size of brain regions across populations. Hence, our data do not provide support for either the EBH or the CBH to explain brain size variation in H. guentheri. Furthermore, brain size variation did not differ between males and females in this species. Our findings suggest that both the variation in temperature and growth season did not shape the variation in brain size in H. guentheri.

scholarly journals Different environmental variables predict body and brain size evolution in Homo

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Manuel Will ◽  
Mario Krapp ◽  
Jay T. Stock ◽  
Andrea Manica
Keyword(s):  
Environmental Factors ◽  
Cognitive Abilities ◽  
Net Primary Productivity ◽  
Brain Size ◽  
Environmental Influence ◽  
Size Variation ◽  
Evolutionary Pattern ◽  
Statistical Framework ◽  
Size Evolution ◽  
Major Predictor

AbstractIncreasing body and brain size constitutes a key macro-evolutionary pattern in the hominin lineage, yet the mechanisms behind these changes remain debated. Hypothesized drivers include environmental, demographic, social, dietary, and technological factors. Here we test the influence of environmental factors on the evolution of body and brain size in the genus Homo over the last one million years using a large fossil dataset combined with global paleoclimatic reconstructions and formalized hypotheses tested in a quantitative statistical framework. We identify temperature as a major predictor of body size variation within Homo, in accordance with Bergmann’s rule. In contrast, net primary productivity of environments and long-term variability in precipitation correlate with brain size but explain low amounts of the observed variation. These associations are likely due to an indirect environmental influence on cognitive abilities and extinction probabilities. Most environmental factors that we test do not correspond with body and brain size evolution, pointing towards complex scenarios which underlie the evolution of key biological characteristics in later Homo.

Brain size evolution in small mammals: test of the expensive tissue hypothesis

Mammalia ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ying Jiang ◽  
Jia Yu Wang ◽  
Xiao Fu Huang ◽  
Chun Lan Mai ◽  
Wen Bo Liao
Keyword(s):  
Small Mammals ◽  
Brain Size ◽  
Reproductive Investment ◽  
Generalized Least Squares ◽  
Offspring Number ◽  
Size Evolution ◽  
Large Brain ◽  
Species Evolution ◽  
The Cost ◽  
Expensive Tissue Hypothesis

Abstract Brain size exhibits significant changes within and between species. Evolution of large brains can be explained by the need to improve cognitive ability for processing more information in changing environments. However, brains are among the most energetically expensive organs. Enlarged brains can impose energetic demands that limit brain size evolution. The expensive tissue hypothesis (ETH) states that a decrease in the size of another expensive tissue, such as the gut, should compensate for the cost of a large brain. We studied the interplay between energetic limitations and brain size evolution in small mammals using phylogenetically generalized least squares (PGLS) regression analysis. Brain mass was not correlated with the length of the digestive tract in 37 species of small mammals after correcting for phylogenetic relationships and body size effects. We further found that the evolution of a large brain was not accompanied by a decrease in male reproductive investments into testes mass and in female reproductive investment into offspring number. The evolution of brain size in small mammals is inconsistent with the prediction of the ETH.

scholarly journals Rethinking the Effects of Body Size on the Study of Brain Size Evolution

2019 ◽  
Vol 93 (4) ◽  
pp. 182-195 ◽  
Author(s):  
Enrique Font ◽  
Roberto García-Roa ◽  
Daniel Pincheira-Donoso ◽  
Pau Carazo
Keyword(s):  
Body Size ◽  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Scaling Effects ◽  
Selection Pressures ◽  
Body Tissues ◽  
Relative Brain Size ◽  
Functional Components ◽  
The Brain

Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g., presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

scholarly journals Beyond brain size

2017 ◽  
Author(s):  
Corina J Logan ◽  
Shahar Avin ◽  
Neeltje Boogert ◽  
Andrew Buskell ◽  
Fiona R. Cross ◽  
...  
Keyword(s):  
Brain Size ◽  
Size Variation ◽  
Brain Evolution ◽  
Simple Relationship ◽  
Cognitive Significance ◽  
Cognitive Measures ◽  
Behavioral Complexity ◽  
Behavioral Traits ◽  
Evolutionary Trajectories ◽  
Brain Behavior

AbstractDespite prolonged interest in comparing brain size and behavioral proxies of ‘intelligence’ across taxa, the adaptive and cognitive significance of brain size variation remains elusive. Central to this problem is the continued focus on hominid cognition as a benchmark, and the assumption that behavioral complexity has a simple relationship with brain size. Although comparative studies of brain size have been criticized for not reflecting how evolution actually operates, and for producing spurious, inconsistent results, the causes of these limitations have received little discussion. We show how these issues arise from implicit assumptions about what brain size measures and how it correlates with behavioral and cognitive traits. We explore how inconsistencies can arise through heterogeneity in evolutionary trajectories and selection pressures on neuroanatomy or neurophysiology across taxa. We examine how interference from ecological and life history variables complicates interpretations of brain-behavior correlations, and point out how this problem is exacerbated by the limitations of brain and cognitive measures. These considerations, and the diversity of brain morphologies and behavioral capacities, suggest that comparative brain-behavior research can make greater progress by focusing on specific neuroanatomical and behavioral traits within relevant ecological and evolutionary contexts. We suggest that a synergistic combination of the ‘bottom up’ approach of classical neuroethology and the ‘top down’ approach of comparative biology/psychology within closely related but behaviorally diverse clades can limit the effects of heterogeneity, interference, and noise. We argue this shift away from broad-scale analyses of superficial phenotypes will provide deeper, more robust insights into brain evolution.

scholarly journals Genes underlying the evolution of tetrapod testes size

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Joanna Baker ◽  
Andrew Meade ◽  
Chris Venditti
Keyword(s):  
Candidate Genes ◽  
Biological Diversity ◽  
Brain Size ◽  
Size Variation ◽  
Phenotypic Change ◽  
Testis Size ◽  
Protein Coding ◽  
Size Evolution ◽  
Size Diversity ◽  
To Come

Abstract Background Testes vary widely in mass relative to body mass across species, but we know very little about which genes underlie and contribute to such variation. This is partly because evidence for which genes are implicated in testis size variation tends to come from investigations involving just one or a few species. Contemporary comparative phylogenetic methods provide an opportunity to test candidate genes for their role in phenotypic change at a macro-evolutionary scale—across species and over millions of years. Previous attempts to detect genotype-phenotype associations across species have been limited in that they can only detect where genes have driven directional selection (e.g. brain size increase). Results Here, we introduce an approach that uses rates of evolutionary change to overcome this limitation to test whether any of twelve candidate genes have driven testis size evolution across tetrapod vertebrates—regardless of directionality. We do this by seeking a relationship between the rates of genetic and phenotypic evolution. Our results reveal five genes (Alkbh5, Dmrtb1, Pld6, Nlrp3, Sp4) that each have played unique and complex roles in tetrapod testis size diversity. In all five genes, we find strong significant associations between the rate of protein-coding substitutions and the rate of testis size evolution. Such an association has never, to our knowledge, been tested before for any gene or phenotype. Conclusions We describe a new approach to tackle one of the most fundamental questions in biology: how do individual genes give rise to biological diversity? The ability to detect genotype-phenotype associations that have acted across species has the potential to build a picture of how natural selection has sculpted phenotypic change over millions of years.

scholarly journals Testing hypotheses of marsupial brain size variation using phylogenetic multiple imputations and a Bayesian comparative framework

2021 ◽  
Vol 288 (1947) ◽  
Author(s):  
Orlin S. Todorov ◽  
Simone P. Blomberg ◽  
Anjali Goswami ◽  
Karen Sears ◽  
Patrik Drhlík ◽  
...  
Keyword(s):  
Litter Size ◽  
Brain Size ◽  
Size Variation ◽  
Reproductive Traits ◽  
Mammalian Brain ◽  
Gestation Length ◽  
High Coverage ◽  
Ecological Predictors ◽  
Size Evolution ◽  
Relative Brain Size

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.

scholarly journals Acrobatic Courtship Display Coevolves with Brain Size in Manakins (Pipridae)

2015 ◽  
Vol 85 (1) ◽  
pp. 29-36 ◽  
Author(s):  
Willow R. Lindsay ◽  
Justin T. Houck ◽  
Claire E. Giuliano ◽  
Lainy B. Day
Keyword(s):  
Sexual Selection ◽  
Cognitive Abilities ◽  
Brain Size ◽  
Brain Evolution ◽  
Neural Systems ◽  
Motor Behaviour ◽  
Size Evolution ◽  
Complex Motor ◽  
Display Behaviour ◽  
Selection For

Acrobatic display behaviour is sexually selected in manakins (Pipridae) and can place high demands on many neural systems. Manakin displays vary across species in terms of behavioural complexity, differing in number of unique motor elements, production of mechanical sounds, cooperation between displaying males, and construction of the display site. Historically, research emphasis has been placed on neurological specializations for vocal aspects of courtship, and less is known about the control of physical, non-vocal displays. By examining brain evolution in relation to extreme acrobatic feats such as manakin displays, we can vastly expand our knowledge of how sexual selection acts on motor behaviour. We tested the hypothesis that sexual selection for complex motor displays has selected for larger brains across the Pipridae. We found that display complexity positively predicts relative brain weight (adjusted for body size) after controlling for phylogeny in 12 manakin species and a closely related flycatcher. This evidence suggests that brain size has evolved in response to sexual selection to facilitate aspects of display such as motor, sensorimotor, perceptual, and cognitive abilities. We show, for the first time, that sexual selection for acrobatic motor behaviour can drive brain size evolution in avian species and, in particular, a family of suboscine birds.

scholarly journals Understanding primate brain evolution

2007 ◽  
Vol 362 (1480) ◽  
pp. 649-658 ◽  
Author(s):  
R.I.M Dunbar ◽  
Susanne Shultz
Keyword(s):  
Life History ◽  
Path Analysis ◽  
Group Size ◽  
Brain Size ◽  
Brain Evolution ◽  
Primate Brain ◽  
The Social ◽  
Large Brain ◽  
Brain Data ◽  
The Relationship

We present a detailed reanalysis of the comparative brain data for primates, and develop a model using path analysis that seeks to present the coevolution of primate brain (neocortex) and sociality within a broader ecological and life-history framework. We show that body size, basal metabolic rate and life history act as constraints on brain evolution and through this influence the coevolution of neocortex size and group size. However, they do not determine either of these variables, which appear to be locked in a tight coevolutionary system. We show that, within primates, this relationship is specific to the neocortex. Nonetheless, there are important constraints on brain evolution; we use path analysis to show that, in order to evolve a large neocortex, a species must first evolve a large brain to support that neocortex and this in turn requires adjustments in diet (to provide the energy needed) and life history (to allow sufficient time both for brain growth and for ‘software’ programming). We review a wider literature demonstrating a tight coevolutionary relationship between brain size and sociality in a range of mammalian taxa, but emphasize that the social brain hypothesis is not about the relationship between brain/neocortex size and group size per se ; rather, it is about social complexity and we adduce evidence to support this. Finally, we consider the wider issue of how mammalian (and primate) brains evolve in order to localize the social effects.

scholarly journals Predator-driven brain size evolution in natural populations of Trinidadian killifish ( Rivulus hartii )

2016 ◽  
Vol 283 (1834) ◽  
pp. 20161075 ◽  
Author(s):  
Matthew R. Walsh ◽  
Whitnee Broyles ◽  
Shannon M. Beston ◽  
Stephan B. Munch
Keyword(s):  
Brain Size ◽  
Natural Populations ◽  
Size Variation ◽  
Laboratory Selection ◽  
Trade Offs ◽  
Female Brain ◽  
Size Evolution ◽  
Selection Experiments ◽  
Fitness Benefits ◽  
Recent Laboratory

Vertebrates exhibit extensive variation in relative brain size. It has long been assumed that this variation is the product of ecologically driven natural selection. Yet, despite more than 100 years of research, the ecological conditions that select for changes in brain size are unclear. Recent laboratory selection experiments showed that selection for larger brains is associated with increased survival in risky environments. Such results lead to the prediction that increased predation should favour increased brain size. Work on natural populations, however, foreshadows the opposite trajectory of evolution; increased predation favours increased boldness, slower learning, and may thereby select for a smaller brain. We tested the influence of predator-induced mortality on brain size evolution by quantifying brain size variation in a Trinidadian killifish, Rivulus hartii , from communities that differ in predation intensity. We observed strong genetic differences in male (but not female) brain size between fish communities; second generation laboratory-reared males from sites with predators exhibited smaller brains than Rivulus from sites in which they are the only fish present. Such trends oppose the results of recent laboratory selection experiments and are not explained by trade-offs with other components of fitness. Our results suggest that increased male brain size is favoured in less risky environments because of the fitness benefits associated with faster rates of learning and problem-solving behaviour.

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