| Records |
| Author |
Dunbar, R.I.M. |
| Title |
Male and female brain evolution is subject to contrasting selection pressures in primates |
Type |
Journal Article |
| Year |
2007 |
Publication |
BMC Biology |
Abbreviated Journal |
BMC Biol |
| Volume |
5 |
Issue  |
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Pages |
21 |
| Keywords |
Animals; *Brain/physiology; *Evolution; Female; Humans; Male; *Selection (Genetics); *Sex Characteristics |
| Abstract |
The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the “social brain” hypothesis) is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20) add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative) is related most closely to neocortex volume, but male sociality (which is more competitive and combative) is more closely related to subcortical units (notably those associated with emotional responses). Thus different brain units have responded to different selection pressures. |
| Address |
British Academy Centenary Research Project, School of Biological Sciences, University of Liverpool, Liverpool, UK. rimd@liv.ac.uk |
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English |
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1741-7007 |
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| Notes |
PMID:17493267 |
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no |
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Serial |
2100 |
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| Author |
Pérez-Barbería, F.J.; Shultz, S.; Dunbar, R.I. |
| Title |
Evidence for coevolution of sociality and relative brain size in three orders of mammals |
Type |
Journal Article |
| Year |
2007 |
Publication |
Evolution |
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| Volume |
61 |
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no |
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Equine Behaviour @ team @ Pérez-Barbería2007 |
Serial |
6221 |
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| Author |
Stanley, C.R.; Dunbar, R.I.M. |
| Title |
Consistent social structure and optimal clique size revealed by social network analysis of feral goats, Capra hircus |
Type |
Journal Article |
| Year |
2013 |
Publication |
Anim Behav |
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| Volume |
85 |
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no |
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Equine Behaviour @ team @ Stanley2013 |
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6253 |
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| Author |
Shi, J.; Dunbar, R.I.M.; Buckland, D.; Miller, D. |
| Title |
Dynamics of grouping patterns and social segregation in feral goats (Capra hircus) on the Isle of Rum, NW Scotland |
Type |
Journal Article |
| Year |
2005 |
Publication |
Mammalia |
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| Volume |
69 |
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no |
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Equine Behaviour @ team @ Shi2005 |
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6257 |
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| Author |
Dunbar, R.I.; Dunbar, E.P. |
| Title |
Contrasts in social structure among black-and-white colobus monkey groups |
Type |
Journal Article |
| Year |
1976 |
Publication |
Animal Behaviour. |
Abbreviated Journal |
Anim. Behav. |
| Volume |
24 |
Issue |
1 |
Pages |
84-92 |
| Keywords |
Agonistic Behavior; Animals; *Colobus; Copulation; Female; *Haplorhini; *Hierarchy, Social; Male; *Social Dominance |
| Abstract |
Three types of Colobus guereza groups may be distinguished on the bases of size and composition, namely small one-male groups, large, one-male groups and multi-male groups. The social structure of each type of group is described in terms of the distribution of non-agonistic interactions, the frequency and distribution of agonistic behaviour and the organization of the roles of vigilance, territorial defence and leadership. A number of differences are found between the group types which appear to be related to the differences in group size and composition. It is suggested that these group types represent stages in the life-cycle of colobus groups, and that such an interpretation may help to resolve some of the conflicting reports in the literature. |
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English |
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0003-3472 |
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| Notes |
PMID:817624 |
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no |
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Serial |
2049 |
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| Author |
O'Connell, S.; Dunbar, R.I.M. |
| Title |
The perception of causality in chimpanzees (Pan spp.) |
Type |
Journal Article |
| Year |
2005 |
Publication |
Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
| Volume |
8 |
Issue |
1 |
Pages |
60-66 |
| Keywords |
Animals; *Association Learning; Awareness; *Concept Formation; Female; *Habituation, Psychophysiologic; Male; Pan paniscus/*psychology; Pan troglodytes/*psychology; Perception |
| Abstract |
Chimpanzees (Pan spp.) were tested on a habituation/dishabituation paradigm that was originally developed to test for comprehension of causality in very young human infants. Three versions of the test were used: a food item being moved by a hand, a human pushing another human off a chair to obtain a food item, and a film clip of natural chimpanzee behaviour (capturing and eating a monkey). Chimpanzees exhibited similar results to those obtained with human infants, with significantly elevated levels of looking on the dishabituation trials. Since the level of response was significantly greater on natural/unnatural sequences than on unnatural/natural sequences, we conclude that the chimpanzees were not responding just to novelty but rather to events that infringed their sense of natural causation. |
| Address |
Evolutionary Psychology Research Group, School of Biological Sciences, Biosciences Building, University of Liverpool, Liverpool, L69 7ZB, UK |
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English |
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Edition |
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| ISSN |
1435-9448 |
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| Notes |
PMID:15322943 |
Approved |
no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
2514 |
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| Author |
Pérez-Barbería, F.J.; Shultz, S.; Dunbar, R.I.M.; Janis, C. |
| Title |
Evidence For Coevolution Of Sociality And Relative Brain Size In Three Orders Of Mammals |
Type |
Journal Article |
| Year |
2007 |
Publication |
Evolution |
Abbreviated Journal |
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| Volume |
61 |
Issue |
12 |
Pages |
2811-2821 |
| Keywords |
Brain size, carnivores, coevolution, primates, sociality, ungulates |
| Abstract |
Abstract
As the brain is responsible for managing an individual's behavioral response to its environment, we should expect that large relative brain size is an evolutionary response to cognitively challenging behaviors. The “social brain hypothesis†argues that maintaining group cohesion is cognitively demanding as individuals living in groups need to be able to resolve conflicts that impact on their ability to meet resource requirements. If sociality does impose cognitive demands, we expect changes in relative brain size and sociality to be coupled over evolutionary time. In this study, we analyze data on sociality and relative brain size for 206 species of ungulates, carnivores, and primates and provide, for the first time, evidence that changes in sociality and relative brain size are closely correlated over evolutionary time for all three mammalian orders. This suggests a process of coevolution and provides support for the social brain theory. However, differences between taxonomic orders in the stability of the transition between small-brained/nonsocial and large-brained/social imply that, although sociality is cognitively demanding, sociality and relative brain size can become decoupled in some cases. Carnivores seem to have been especially prone to this. |
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doi: 10.1111/j.1558-5646.2007.00229.x |
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no |
| Call Number |
Equine Behaviour @ team @ |
Serial |
4781 |
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| Author |
Joffe, T.H.; Dunbar, R.I. |
| Title |
Visual and socio-cognitive information processing in primate brain evolution |
Type |
Journal Article |
| Year |
1997 |
Publication |
Proceedings. Biological Sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
264 |
Issue |
1386 |
Pages |
1303-1307 |
| Keywords |
Animals; Brain/anatomy & histology/*physiology; Cognition/physiology; *Evolution; Geniculate Bodies/anatomy & histology/physiology; Humans; Mental Processes/physiology; Neocortex/physiology; Primates/anatomy & histology/*physiology/*psychology; *Social Behavior; Visual Cortex/anatomy & histology/physiology |
| Abstract |
Social group size has been shown to correlate with neocortex size in primates. Here we use comparative analyses to show that social group size is independently correlated with the size of non-V1 neocortical areas, but not with other more proximate components of the visual system or with brain systems associated with emotional cueing (e.g. the amygdala). We argue that visual brain components serve as a social information 'input device' for socio-visual stimuli such as facial expressions, bodily gestures and visual status markers, while the non-visual neocortex serves as a 'processing device' whereby these social cues are encoded, interpreted and associated with stored information. However, the second appears to have greater overall importance because the size of the V1 visual area appears to reach an asymptotic size beyond which visual acuity and pattern recognition may not improve significantly. This is especially true of the great ape clade (including humans), that is known to use more sophisticated social cognitive strategies. |
| Address |
School of Life Sciences, University of Liverpool, UK |
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English |
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0962-8452 |
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| Notes |
PMID:9332015 |
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no |
| Call Number |
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Serial |
2095 |
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| Author |
Dunbar, R.I.M.; Shultz, S. |
| Title |
Understanding primate brain evolution |
Type |
Journal Article |
| Year |
2007 |
Publication |
Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |
Abbreviated Journal |
Philos Trans R Soc Lond B Biol Sci |
| Volume |
362 |
Issue |
1480 |
Pages |
649-658 |
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| Abstract |
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. |
| Address |
British Academy Centenary Research Project, School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, UK. rimd@liv.ac.uk |
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English |
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0962-8436 |
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| Notes |
PMID:17301028 |
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no |
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Serial |
2099 |
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| Author |
Zhou, W.-X.; Sornette, D.; Hill, R.A.; Dunbar, R.I.M. |
| Title |
Discrete hierarchical organization of social group sizes |
Type |
Journal Article |
| Year |
2005 |
Publication |
Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
| Volume |
272 |
Issue |
1561 |
Pages |
439-444 |
| Keywords |
Anthropology, Cultural; *Group Structure; Humans; *Models, Biological; *Social Behavior; *Social Environment |
| Abstract |
The 'social brain hypothesis' for the evolution of large brains in primates has led to evidence for the coevolution of neocortical size and social group sizes, suggesting that there is a cognitive constraint on group size that depends, in some way, on the volume of neural material available for processing and synthesizing information on social relationships. More recently, work on both human and non-human primates has suggested that social groups are often hierarchically structured. We combine data on human grouping patterns in a comprehensive and systematic study. Using fractal analysis, we identify, with high statistical confidence, a discrete hierarchy of group sizes with a preferred scaling ratio close to three: rather than a single or a continuous spectrum of group sizes, humans spontaneously form groups of preferred sizes organized in a geometrical series approximating 3-5, 9-15, 30-45, etc. Such discrete scale invariance could be related to that identified in signatures of herding behaviour in financial markets and might reflect a hierarchical processing of social nearness by human brains. |
| Address |
State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237, China |
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English |
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0962-8452 |
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PMID:15734699 |
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no |
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refbase @ user @ |
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549 |
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