Robert Barton | Durham University (original) (raw)
Papers by Robert Barton
Proceedings of The Royal Society B: Biological Sciences, Sep 14, 2016
Phenotypic traits are products of two processes: evolution and development. But how do these proc... more Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of mosaic change at the level of the functional systems and more complex genetic and developmental mechanisms. These hypotheses are not mutually exclusive but make different predictions. We review recent genetic and neurodevelopmental evidence, concluding that functional rather than developmental constraints are the main cause of the observed patterns.
Nature Ecology & Evolution, 2024
Despite decades of comparative studies, puzzling aspects of the relationship between mammalian br... more Despite decades of comparative studies, puzzling aspects of the relationship
between mammalian brain and body mass continue to defy satisfactory
explanation. Here we show that several such aspects arise from routinely
fitting log-linear models to the data: the correlated evolution of brain and
body mass is in fact log-curvilinear. This simultaneously accounts for several
phenomena for which diverse biological explanations have been proposed,
notably variability in scaling coefficients across clades, low encephalization
in larger species and the so-called taxon-level problem. Our model implies
a need to revisit previous findings about relative brain mass. Accounting
for the true scaling relationship, we document dramatically varying rates
of relative brain mass evolution across the mammalian phylogeny, and we
resolve the question of whether there is an overall trend for brain mass to
increase through time. We find a trend in only three mammalian orders,
which is by far the strongest in primates, setting the stage for the uniquely
rapid directional increase ultimately producing the computational powers
of the human brain.
Supplementary material from "Maternal investment, life histories and the evolution of brain structure in primates
Life history is a robust correlate of relative brain size: larger-brained mammals and birds have ... more Life history is a robust correlate of relative brain size: larger-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. The Cognitive buffer hypothesis (CBH) proposes an adaptive explanation for this relationship: large brains may permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing for reduced mortality and increased lifespan. By contrast, the Developmental costs hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains, predicting correlations with pre-adult life-history phases. Here, we test novel predictions of the hypotheses in primates applied to the neocortex and cerebellum, two major brain structures with distinct developmental trajectories. While neocortical growth is allocated primarily to prenatal development, the cerebellum exhibits relatively substantial post-natal growth. Consistent with the DCH, neocortical expansion is related primarily to extended gestation while cerebellar expansion to extended post-natal development, particularly the juvenile period. Contrary to the CBH, adult lifespan explains relatively little variance in the whole brain or neocortex volume once pre-adult life-history phases are accounted for. Only the cerebellum shows a relationship with lifespan after accounting for developmental periods. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental phases and imply that environmental input during post-natal maturation may be particularly crucial for the development of cerebellar function. They also suggest that relatively extended maturation times provide a developmental mechanism for the marked expansion of the cerebellum in the apes.
Cambridge University Press eBooks, 2001
Proceedings of The Royal Society B: Biological Sciences, Oct 18, 2017
Comparative studies have identified a wide range of behavioural and ecological correlates of rela... more Comparative studies have identified a wide range of behavioural and ecological correlates of relative brain size, with results differing between taxonomic groups, and even within them. In primates for example, recent studies contradict one another over whether social or ecological factors are critical. A basic assumption of such studies is that with sufficiently large samples and appropriate analysis, robust correlations indicative of selection pressures on cognition will emerge. We carried out a comprehensive re-examination of correlates of primate brain size using two large comparative datasets and phylogenetic comparative methods. We found evidence in both datasets for associations between brain size and ecological variables (home range size, diet and activity period), but little evidence for an effect of social group size, a correlation which has previously formed the empirical basis of the Social Brain Hypothesis. However, reflecting divergent results in the literature, our results exhibited instability across datasets, even when they were matched for species composition and predictor variables. We identify several potential empirical and theoretical difficulties underlying this instability and suggest that these issues raise doubts about inferring cognitive selection pressures from behavioural correlates of brain size.
Ecological constraints on mammalian sleep architecture
Cambridge University Press eBooks, 2001
In this chapter, we review the evidence for how ecological factors, including predation risk and ... more In this chapter, we review the evidence for how ecological factors, including predation risk and foraging requirements, might shape patterns of sleep among mammals. We also highlight the need for more research on the degree to which animals can exhibit flexibility in their sleep requirements, as such plasticity could provide a means to overcome constraints, particularly when the costs associated with sleep vary on daily or seasonal time scales. We begin by discussing if the available data are informative and appropriate for studying the role of ecology in the evolution of sleep architecture. We then move on to review how different characteristics of sleep have evolved alongside one another, as these traits form the foundation for our discussion of ecological constraints that follows. We restrict our discussion to terrestrial mammals and exclude monotremes, such as the platypus (Ornithorhynchus anatinus) and echidna. Aquatic mammals, in fact, exhibit a different sleep architecture, and it is still uncertain whether monotremes possess two distinct sleep states—rapid-eye-movement (REM) and non-REM (NREM) sleep—as is observed in most other mammals. We note, however, that the dramatic differences in sleep characteristics of terrestrial and aquatic mammals provide evidence for the claim that ecology influences sleep architecture. In aquatic environments, mammals appear to forego REM sleep—or at least REM indices are truncated in aquatic species relative to the range of values seen in terrestrial species—and unihemispheric NREM sleep is found. Some authors argue that the evolution of unihemispheric sleep and suppression of REM sleep, with its associated paralysis, allows cetaceans and eared seals to maintain the motor activity necessary to surface and breathe, while others suggest unihemispheric sleep might facilitate predator detection or help balance heat loss to the water by constantly swimming.
Philosophical Transactions of the Royal Society B, Dec 27, 2021
The anthropoid primates are known for their intense sociality and large brain size. The idea that... more 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’.
Evolution of the social brain
Cambridge University Press eBooks, Sep 25, 1997
... President of the Royal Society (London) suggested that every-thing of great importance had al... more ... President of the Royal Society (London) suggested that every-thing of great importance had already ... have evolved to do, it is not a collection of simple biological routines (Mithen, 1996 ... acceptance, even when combined in synthetic models and causally linked to social dynamics. ...
Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores
Philosophical Transactions of the Royal Society B, Jun 29, 1995
How brains have evolved in response to particular selection pressures is illuminated by ecologica... more How brains have evolved in response to particular selection pressures is illuminated by ecological correlates of differences in brain structure among contemporary species. The focus of most comparative studies has been on the overall size of brains relative to body size, hence ignoring the ways in which selection operates on specific neural systems. Here we investigate evolutionary radiations in the size of visual and olfactory brain structures within three orders of mammals: primates, bats and insectivores. The comparative relationships within these three orders show both similarities and differences. After removal of the allometric effect of overall brain size, the sizes of different structures within each sensory modality are positively correlated in all three orders. Correlations between visual and olfactory structures, however, are negative in primates, negative but non-significant in insectivores, and positive in bats. In both primates and insectivores, nocturnal lineages tend to have larger olfactory structures than do diurnal or partly diurnal lineages, and among the primates diurnal lineages have larger striate visual cortexes. Hence the apparent trade-off between vision and olfaction in primates seems to be related to the divergence of nocturnal and diurnal forms. However, negative correlations between visual and olfactory structures were also found when nocturnal strepsirhines and diurnal haplorhines were analysed separately, suggesting that ecological variables in addition to activity timing may be significant. Indeed, there were also associations with diet: frugivory was associated with enlargements of the geniculostriate visual system in diurnal primates, enlargements of olfactory structures in nocturnal primates, and possibly enlargements of both in bats. Further ecological associations were found within insectivores: aquatic lineages had smaller olfactory structures than in their non-aquatic counterparts, and fossorial lineages had smaller optic nerves than in non-fossorial forms. We conclude that activity timing, diet and habitat have each played a role in the evolutionary radiation of mammalian sensory systems, but with varying effects in the different taxa. Some of the associations between ecology and sensory systems suggest alternative explanations for correlates of overall brain size, which have in the past commonly been interpreted in terms of selection on intelligence.
Evolution of Sleep
Cambridge University Press eBooks, 2001
1. Introduction Patrick McNamara, Charles L. Nunn and Robert A. Barton 2. Ecological constraints ... more 1. Introduction Patrick McNamara, Charles L. Nunn and Robert A. Barton 2. Ecological constraints on mammalian sleep architecture Isabella Capellini, Brian T. Preston, Patrick McNamara, Robert A. Barton and Charles L. Nunn 3. Sleep in insects Kristyna M. Hartse 4. Schooling by continuously-active fishes: clues to sleep's ultimate function J. Lee Kavanau 5. What exactly is it that sleeps?: the evolution, regulation and organization of an emergent network property James M. Krueger 6. Evolutionary medicine of sleep disorders: toward a science of sleep duration Patrick McNamara and Sanford Auerbach 7. Primate sleep in phylogenetic perspective Charles N. Nunn, Patrick McNamara, Isabella Capellini, Brian T. Preston and Robert Barton 8. A bird's eye view on the function of sleep Niels C. Rattenborg and Charles J. Amlaner 9. The evolution of wakefulness: from reptiles to mammals Ruben V. Rial, Mourad Akaarir, Antoni Gamundi, M. Cristina Nicolau and Susana Esteban 10. Evolution of REM sleep Mahesh M. Thakkar and Subimal Datta 11. Towards the understanding of the function of sleep: new insights from mouse genetics Valter Tucci and Patrick M. Nolan 12. Fishing for sleep Irina V. Zhdanova.
Journal of Personality and Social Psychology, 2019
Perceptions of physical attractiveness vary across cultural groups, particularly for female body ... more Perceptions of physical attractiveness vary across cultural groups, particularly for female body size and shape. It has been hypothesised that visual media propagates Western 'thin ideals'. However, because cross-cultural studies typically consider groups highly differentiated on a number of factors, identifying the causal factors has thus far been impossible. In the present research, we conducted 'naturalistic' and controlled experiments to test the influence of media access on female body ideals in a remote region of Nicaragua by sampling from villages with and without regular television access. We found that greater television consumption remained a significant predictor of preferences for slimmer, curvier female figures after controlling for a range of other factors in an ethnically balanced sample of 299 individuals (150 female, aged 15-79) across 7 villages. Within-individual analyses in one village over 3 years also showed an association between increased TV consumption and preferences for slimmer figures amongst some participants. Finally, an experimental study in two low-media locations demonstrates that exposure to media images of fashion models can directly impact participants' body size ideals. We thus provide the first converging cross-sectional, longitudinal and experimental evidence from field-based research, that media exposure can drive changes in perceptions of female attractiveness.
Life history is a robust correlate of relative brain size: larger-brained mammals and birds have ... more Life history is a robust correlate of relative brain size: larger-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. The cognitive buffer hypothesis (CBH) proposes an adaptive explanation for this relationship: large brains may permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing for reduced mortality and increased lifespan. By contrast, the developmental costs hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains, predicting correlations with pre-adult life-history phases. Here, we test novel predictions of the hypotheses in primates applied to the neocortex and cerebellum, two major brain structures with distinct developmental trajectories. While neocortical growth is allocated primarily to pre-natal development, the cerebellum exhibits relatively substantial post-natal growth. Consistent with the DCH, neocortical expansion is related primarily to extended gestation while cerebellar expansion to extended post-natal development, particularly the juvenile period. Contrary to the CBH, adult lifespan explains relatively little variance in the whole brain or neocortex volume once pre-adult life-history phases are accounted for. Only the cerebellum shows a relationship with lifespan after accounting for developmental periods. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental phases, and imply that environmental input during post-natal maturation may be particularly crucial for the development of cerebellar function. They also suggest that relatively extended post-natal maturation times provide a developmental mechanism for the marked expansion of the cerebellum in the apes.
Scientific reports, Jan 16, 2017
Television consumption influences perceptions of attractive female body size. However, cross-cult... more Television consumption influences perceptions of attractive female body size. However, cross-cultural research examining media influence on body ideals is typically confounded by differences in the availability of reliable and diverse foodstuffs. 112 participants were recruited from 3 Nicaraguan villages that differed in television consumption and nutritional status, such that the contribution of both factors could be revealed. Participants completed a female figure preference task, reported their television consumption, and responded to several measures assessing nutritional status. Communities with higher television consumption and/or higher nutritional status preferred thinner female bodies than communities with lower television consumption and/or lower nutritional status. Bayesian mixed models estimated the plausible range of effects for television consumption, nutritional status, and other relevant variables on individual preferences. The model explained all meaningful differen...
British Journal of Psychology, 2016
Internalisation of a thin ideal has been posited as a key risk factor in the development of patho... more Internalisation of a thin ideal has been posited as a key risk factor in the development of pathological eating attitudes. Cross-culturally, studies have found a preference for heavier bodies in populations with reduced access to visual media compared to Western populations. As yet, however, there has been little attempt to control for confounding variables in order to isolate the effects of media exposure from other cultural and ecological factors. Here we examined preferences for female body size in relation to television consumption in Nicaraguan men and women, while controlling for the potential confounding effects of hunger and other sources of Westernization. We included an urban sample, a sample from a village with established television access, and a sample from a nearby village with very limited television access. The highest BMI preferences were found in the village with least media access, while the lowest BMI preferences were found in the urban sample. Data from the rural sample with established television access were intermediate between the two. Amongst rural women in particular, greater television consumption was a stronger predictor of body weight preferences than acculturation, education, hunger, or income. We also found some evidence for television consumption increasing the likelihood of women seeking to lose weight, possibly via body shape preferences. Overall, these results strongly implicate television access in establishing risk factors for body image disturbances in populations newly exposed to Western media.
Wearing Red Enhances Perceived Dominance, Aggression and Confidence
Red colouration is a sexually selected trait associated with dominance in a variety of animal tax... more Red colouration is a sexually selected trait associated with dominance in a variety of animal taxa, and has similar psychological and cultural associations in humans. Both natural and artificial red stimuli have been found to exploit these innate biases. Because human skin redness varies with health, hormones and emotional state, I hypothesised that artificial red stimuli may exploit a perceptual bias that evolved to support rapid social judgements. In order to test this I experimentally investigated whether wearing red influences perceived personality attributes relative to blue or grey clothing, and whether results vary with gender. One hundred subjects (50 males and 50 females, average age 22.97) rated digitally manipulated photos of men for trustworthiness, aggression, dominance, and confidence on a 7-point scale. Each image was presented in three chromatically manipulated conditions (red, blue and grey), adjusted for luminance. Participants also categorised the emotional state ...
Evolutionary Anthropology: Issues, News, and Reviews, 2016
This article may be used for non-commercial purposes in accordance With Wiley Terms and Condition... more This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving. Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.
It is widely assumed that the cortex is the "pinnacle" of brain evolution. This assumption stems ... more It is widely assumed that the cortex is the "pinnacle" of brain evolution. This assumption stems primarily from the simplistic observations that the human cortex is large, conspicuous and increased disproportionately in relation to overall brain size over evolutionary time. It is reinforced by a persistent implicit dualism in the culture of cognitive neuroscience, by the focus of techniques such as fMRI on cortical areas, and by anthropocentric teleology in evolutionary cognitive neuroscience (exemplified by the common use of the terms "higher" and "advanced" applied to the term "cognition"). I argue that cortico-centric biases have resulted in a distorted view of brain evolution and functional anatomy, and continue to hinder progress in research. Contrary to these biases, I show that the proportional volume of a brain component is not a good indicator of its functional importance, that cortical-subcortical connectivity and correlated change is key to understanding how brains evolved, and that subcortical structures contribute to a wide range of cognitive functions, including those considered distinctively human. Approaches which focus on cortical-subcortical interactions are opening up fresh pathways to understanding neuro-cognitive evolution and repudiate the notion that the cortex is the locus of all the interesting action-evolutionarily, neurobiologically, and cognitively.
Behavioral and Brain Sciences
Burkart et al. conflate the domain-specificity of cognitive processes with the statistical patter... more Burkart et al. conflate the domain-specificity of cognitive processes with the statistical pattern of variance in behavioural measures that partly reflect those processes. General intelligence is a statistical abstraction, not a cognitive trait, and we argue that the former does not warrant inferences about the nature or evolution of the latter.
Proceedings. Biological sciences, Sep 14, 2016
Phenotypic traits are products of two processes: evolution and development. But how do these proc... more Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of...
Brain, behavior and evolution, Jan 12, 2016
Proceedings of The Royal Society B: Biological Sciences, Sep 14, 2016
Phenotypic traits are products of two processes: evolution and development. But how do these proc... more Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of mosaic change at the level of the functional systems and more complex genetic and developmental mechanisms. These hypotheses are not mutually exclusive but make different predictions. We review recent genetic and neurodevelopmental evidence, concluding that functional rather than developmental constraints are the main cause of the observed patterns.
Nature Ecology & Evolution, 2024
Despite decades of comparative studies, puzzling aspects of the relationship between mammalian br... more Despite decades of comparative studies, puzzling aspects of the relationship
between mammalian brain and body mass continue to defy satisfactory
explanation. Here we show that several such aspects arise from routinely
fitting log-linear models to the data: the correlated evolution of brain and
body mass is in fact log-curvilinear. This simultaneously accounts for several
phenomena for which diverse biological explanations have been proposed,
notably variability in scaling coefficients across clades, low encephalization
in larger species and the so-called taxon-level problem. Our model implies
a need to revisit previous findings about relative brain mass. Accounting
for the true scaling relationship, we document dramatically varying rates
of relative brain mass evolution across the mammalian phylogeny, and we
resolve the question of whether there is an overall trend for brain mass to
increase through time. We find a trend in only three mammalian orders,
which is by far the strongest in primates, setting the stage for the uniquely
rapid directional increase ultimately producing the computational powers
of the human brain.
Supplementary material from "Maternal investment, life histories and the evolution of brain structure in primates
Life history is a robust correlate of relative brain size: larger-brained mammals and birds have ... more Life history is a robust correlate of relative brain size: larger-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. The Cognitive buffer hypothesis (CBH) proposes an adaptive explanation for this relationship: large brains may permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing for reduced mortality and increased lifespan. By contrast, the Developmental costs hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains, predicting correlations with pre-adult life-history phases. Here, we test novel predictions of the hypotheses in primates applied to the neocortex and cerebellum, two major brain structures with distinct developmental trajectories. While neocortical growth is allocated primarily to prenatal development, the cerebellum exhibits relatively substantial post-natal growth. Consistent with the DCH, neocortical expansion is related primarily to extended gestation while cerebellar expansion to extended post-natal development, particularly the juvenile period. Contrary to the CBH, adult lifespan explains relatively little variance in the whole brain or neocortex volume once pre-adult life-history phases are accounted for. Only the cerebellum shows a relationship with lifespan after accounting for developmental periods. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental phases and imply that environmental input during post-natal maturation may be particularly crucial for the development of cerebellar function. They also suggest that relatively extended maturation times provide a developmental mechanism for the marked expansion of the cerebellum in the apes.
Cambridge University Press eBooks, 2001
Proceedings of The Royal Society B: Biological Sciences, Oct 18, 2017
Comparative studies have identified a wide range of behavioural and ecological correlates of rela... more Comparative studies have identified a wide range of behavioural and ecological correlates of relative brain size, with results differing between taxonomic groups, and even within them. In primates for example, recent studies contradict one another over whether social or ecological factors are critical. A basic assumption of such studies is that with sufficiently large samples and appropriate analysis, robust correlations indicative of selection pressures on cognition will emerge. We carried out a comprehensive re-examination of correlates of primate brain size using two large comparative datasets and phylogenetic comparative methods. We found evidence in both datasets for associations between brain size and ecological variables (home range size, diet and activity period), but little evidence for an effect of social group size, a correlation which has previously formed the empirical basis of the Social Brain Hypothesis. However, reflecting divergent results in the literature, our results exhibited instability across datasets, even when they were matched for species composition and predictor variables. We identify several potential empirical and theoretical difficulties underlying this instability and suggest that these issues raise doubts about inferring cognitive selection pressures from behavioural correlates of brain size.
Ecological constraints on mammalian sleep architecture
Cambridge University Press eBooks, 2001
In this chapter, we review the evidence for how ecological factors, including predation risk and ... more In this chapter, we review the evidence for how ecological factors, including predation risk and foraging requirements, might shape patterns of sleep among mammals. We also highlight the need for more research on the degree to which animals can exhibit flexibility in their sleep requirements, as such plasticity could provide a means to overcome constraints, particularly when the costs associated with sleep vary on daily or seasonal time scales. We begin by discussing if the available data are informative and appropriate for studying the role of ecology in the evolution of sleep architecture. We then move on to review how different characteristics of sleep have evolved alongside one another, as these traits form the foundation for our discussion of ecological constraints that follows. We restrict our discussion to terrestrial mammals and exclude monotremes, such as the platypus (Ornithorhynchus anatinus) and echidna. Aquatic mammals, in fact, exhibit a different sleep architecture, and it is still uncertain whether monotremes possess two distinct sleep states—rapid-eye-movement (REM) and non-REM (NREM) sleep—as is observed in most other mammals. We note, however, that the dramatic differences in sleep characteristics of terrestrial and aquatic mammals provide evidence for the claim that ecology influences sleep architecture. In aquatic environments, mammals appear to forego REM sleep—or at least REM indices are truncated in aquatic species relative to the range of values seen in terrestrial species—and unihemispheric NREM sleep is found. Some authors argue that the evolution of unihemispheric sleep and suppression of REM sleep, with its associated paralysis, allows cetaceans and eared seals to maintain the motor activity necessary to surface and breathe, while others suggest unihemispheric sleep might facilitate predator detection or help balance heat loss to the water by constantly swimming.
Philosophical Transactions of the Royal Society B, Dec 27, 2021
The anthropoid primates are known for their intense sociality and large brain size. The idea that... more 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’.
Evolution of the social brain
Cambridge University Press eBooks, Sep 25, 1997
... President of the Royal Society (London) suggested that every-thing of great importance had al... more ... President of the Royal Society (London) suggested that every-thing of great importance had already ... have evolved to do, it is not a collection of simple biological routines (Mithen, 1996 ... acceptance, even when combined in synthetic models and causally linked to social dynamics. ...
Evolutionary radiation of visual and olfactory brain systems in primates, bats and insectivores
Philosophical Transactions of the Royal Society B, Jun 29, 1995
How brains have evolved in response to particular selection pressures is illuminated by ecologica... more How brains have evolved in response to particular selection pressures is illuminated by ecological correlates of differences in brain structure among contemporary species. The focus of most comparative studies has been on the overall size of brains relative to body size, hence ignoring the ways in which selection operates on specific neural systems. Here we investigate evolutionary radiations in the size of visual and olfactory brain structures within three orders of mammals: primates, bats and insectivores. The comparative relationships within these three orders show both similarities and differences. After removal of the allometric effect of overall brain size, the sizes of different structures within each sensory modality are positively correlated in all three orders. Correlations between visual and olfactory structures, however, are negative in primates, negative but non-significant in insectivores, and positive in bats. In both primates and insectivores, nocturnal lineages tend to have larger olfactory structures than do diurnal or partly diurnal lineages, and among the primates diurnal lineages have larger striate visual cortexes. Hence the apparent trade-off between vision and olfaction in primates seems to be related to the divergence of nocturnal and diurnal forms. However, negative correlations between visual and olfactory structures were also found when nocturnal strepsirhines and diurnal haplorhines were analysed separately, suggesting that ecological variables in addition to activity timing may be significant. Indeed, there were also associations with diet: frugivory was associated with enlargements of the geniculostriate visual system in diurnal primates, enlargements of olfactory structures in nocturnal primates, and possibly enlargements of both in bats. Further ecological associations were found within insectivores: aquatic lineages had smaller olfactory structures than in their non-aquatic counterparts, and fossorial lineages had smaller optic nerves than in non-fossorial forms. We conclude that activity timing, diet and habitat have each played a role in the evolutionary radiation of mammalian sensory systems, but with varying effects in the different taxa. Some of the associations between ecology and sensory systems suggest alternative explanations for correlates of overall brain size, which have in the past commonly been interpreted in terms of selection on intelligence.
Evolution of Sleep
Cambridge University Press eBooks, 2001
1. Introduction Patrick McNamara, Charles L. Nunn and Robert A. Barton 2. Ecological constraints ... more 1. Introduction Patrick McNamara, Charles L. Nunn and Robert A. Barton 2. Ecological constraints on mammalian sleep architecture Isabella Capellini, Brian T. Preston, Patrick McNamara, Robert A. Barton and Charles L. Nunn 3. Sleep in insects Kristyna M. Hartse 4. Schooling by continuously-active fishes: clues to sleep's ultimate function J. Lee Kavanau 5. What exactly is it that sleeps?: the evolution, regulation and organization of an emergent network property James M. Krueger 6. Evolutionary medicine of sleep disorders: toward a science of sleep duration Patrick McNamara and Sanford Auerbach 7. Primate sleep in phylogenetic perspective Charles N. Nunn, Patrick McNamara, Isabella Capellini, Brian T. Preston and Robert Barton 8. A bird's eye view on the function of sleep Niels C. Rattenborg and Charles J. Amlaner 9. The evolution of wakefulness: from reptiles to mammals Ruben V. Rial, Mourad Akaarir, Antoni Gamundi, M. Cristina Nicolau and Susana Esteban 10. Evolution of REM sleep Mahesh M. Thakkar and Subimal Datta 11. Towards the understanding of the function of sleep: new insights from mouse genetics Valter Tucci and Patrick M. Nolan 12. Fishing for sleep Irina V. Zhdanova.
Journal of Personality and Social Psychology, 2019
Perceptions of physical attractiveness vary across cultural groups, particularly for female body ... more Perceptions of physical attractiveness vary across cultural groups, particularly for female body size and shape. It has been hypothesised that visual media propagates Western 'thin ideals'. However, because cross-cultural studies typically consider groups highly differentiated on a number of factors, identifying the causal factors has thus far been impossible. In the present research, we conducted 'naturalistic' and controlled experiments to test the influence of media access on female body ideals in a remote region of Nicaragua by sampling from villages with and without regular television access. We found that greater television consumption remained a significant predictor of preferences for slimmer, curvier female figures after controlling for a range of other factors in an ethnically balanced sample of 299 individuals (150 female, aged 15-79) across 7 villages. Within-individual analyses in one village over 3 years also showed an association between increased TV consumption and preferences for slimmer figures amongst some participants. Finally, an experimental study in two low-media locations demonstrates that exposure to media images of fashion models can directly impact participants' body size ideals. We thus provide the first converging cross-sectional, longitudinal and experimental evidence from field-based research, that media exposure can drive changes in perceptions of female attractiveness.
Life history is a robust correlate of relative brain size: larger-brained mammals and birds have ... more Life history is a robust correlate of relative brain size: larger-brained mammals and birds have slower life histories and longer lifespans than smaller-brained species. The cognitive buffer hypothesis (CBH) proposes an adaptive explanation for this relationship: large brains may permit greater behavioural flexibility and thereby buffer the animal from unpredictable environmental challenges, allowing for reduced mortality and increased lifespan. By contrast, the developmental costs hypothesis (DCH) suggests that life-history correlates of brain size reflect the extension of maturational processes needed to accommodate the evolution of large brains, predicting correlations with pre-adult life-history phases. Here, we test novel predictions of the hypotheses in primates applied to the neocortex and cerebellum, two major brain structures with distinct developmental trajectories. While neocortical growth is allocated primarily to pre-natal development, the cerebellum exhibits relatively substantial post-natal growth. Consistent with the DCH, neocortical expansion is related primarily to extended gestation while cerebellar expansion to extended post-natal development, particularly the juvenile period. Contrary to the CBH, adult lifespan explains relatively little variance in the whole brain or neocortex volume once pre-adult life-history phases are accounted for. Only the cerebellum shows a relationship with lifespan after accounting for developmental periods. Our results substantiate and elaborate on the role of maternal investment and offspring development in brain evolution, suggest that brain components can evolve partly independently through modifications of distinct developmental phases, and imply that environmental input during post-natal maturation may be particularly crucial for the development of cerebellar function. They also suggest that relatively extended post-natal maturation times provide a developmental mechanism for the marked expansion of the cerebellum in the apes.
Scientific reports, Jan 16, 2017
Television consumption influences perceptions of attractive female body size. However, cross-cult... more Television consumption influences perceptions of attractive female body size. However, cross-cultural research examining media influence on body ideals is typically confounded by differences in the availability of reliable and diverse foodstuffs. 112 participants were recruited from 3 Nicaraguan villages that differed in television consumption and nutritional status, such that the contribution of both factors could be revealed. Participants completed a female figure preference task, reported their television consumption, and responded to several measures assessing nutritional status. Communities with higher television consumption and/or higher nutritional status preferred thinner female bodies than communities with lower television consumption and/or lower nutritional status. Bayesian mixed models estimated the plausible range of effects for television consumption, nutritional status, and other relevant variables on individual preferences. The model explained all meaningful differen...
British Journal of Psychology, 2016
Internalisation of a thin ideal has been posited as a key risk factor in the development of patho... more Internalisation of a thin ideal has been posited as a key risk factor in the development of pathological eating attitudes. Cross-culturally, studies have found a preference for heavier bodies in populations with reduced access to visual media compared to Western populations. As yet, however, there has been little attempt to control for confounding variables in order to isolate the effects of media exposure from other cultural and ecological factors. Here we examined preferences for female body size in relation to television consumption in Nicaraguan men and women, while controlling for the potential confounding effects of hunger and other sources of Westernization. We included an urban sample, a sample from a village with established television access, and a sample from a nearby village with very limited television access. The highest BMI preferences were found in the village with least media access, while the lowest BMI preferences were found in the urban sample. Data from the rural sample with established television access were intermediate between the two. Amongst rural women in particular, greater television consumption was a stronger predictor of body weight preferences than acculturation, education, hunger, or income. We also found some evidence for television consumption increasing the likelihood of women seeking to lose weight, possibly via body shape preferences. Overall, these results strongly implicate television access in establishing risk factors for body image disturbances in populations newly exposed to Western media.
Wearing Red Enhances Perceived Dominance, Aggression and Confidence
Red colouration is a sexually selected trait associated with dominance in a variety of animal tax... more Red colouration is a sexually selected trait associated with dominance in a variety of animal taxa, and has similar psychological and cultural associations in humans. Both natural and artificial red stimuli have been found to exploit these innate biases. Because human skin redness varies with health, hormones and emotional state, I hypothesised that artificial red stimuli may exploit a perceptual bias that evolved to support rapid social judgements. In order to test this I experimentally investigated whether wearing red influences perceived personality attributes relative to blue or grey clothing, and whether results vary with gender. One hundred subjects (50 males and 50 females, average age 22.97) rated digitally manipulated photos of men for trustworthiness, aggression, dominance, and confidence on a 7-point scale. Each image was presented in three chromatically manipulated conditions (red, blue and grey), adjusted for luminance. Participants also categorised the emotional state ...
Evolutionary Anthropology: Issues, News, and Reviews, 2016
This article may be used for non-commercial purposes in accordance With Wiley Terms and Condition... more This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving. Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.
It is widely assumed that the cortex is the "pinnacle" of brain evolution. This assumption stems ... more It is widely assumed that the cortex is the "pinnacle" of brain evolution. This assumption stems primarily from the simplistic observations that the human cortex is large, conspicuous and increased disproportionately in relation to overall brain size over evolutionary time. It is reinforced by a persistent implicit dualism in the culture of cognitive neuroscience, by the focus of techniques such as fMRI on cortical areas, and by anthropocentric teleology in evolutionary cognitive neuroscience (exemplified by the common use of the terms "higher" and "advanced" applied to the term "cognition"). I argue that cortico-centric biases have resulted in a distorted view of brain evolution and functional anatomy, and continue to hinder progress in research. Contrary to these biases, I show that the proportional volume of a brain component is not a good indicator of its functional importance, that cortical-subcortical connectivity and correlated change is key to understanding how brains evolved, and that subcortical structures contribute to a wide range of cognitive functions, including those considered distinctively human. Approaches which focus on cortical-subcortical interactions are opening up fresh pathways to understanding neuro-cognitive evolution and repudiate the notion that the cortex is the locus of all the interesting action-evolutionarily, neurobiologically, and cognitively.
Behavioral and Brain Sciences
Burkart et al. conflate the domain-specificity of cognitive processes with the statistical patter... more Burkart et al. conflate the domain-specificity of cognitive processes with the statistical pattern of variance in behavioural measures that partly reflect those processes. General intelligence is a statistical abstraction, not a cognitive trait, and we argue that the former does not warrant inferences about the nature or evolution of the latter.
Proceedings. Biological sciences, Sep 14, 2016
Phenotypic traits are products of two processes: evolution and development. But how do these proc... more Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of...
Brain, behavior and evolution, Jan 12, 2016