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Author Dunbar, R.I.M.; Shultz, S. doi  openurl
  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 (down) 362 Issue 1480 Pages 649-658  
  Keywords  
  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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  Language English Summary Language Original Title  
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  Series Volume Series Issue Edition  
  ISSN 0962-8436 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:17301028 Approved no  
  Call Number Serial 2099  
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Author Dunbar, R.I.M.; Shultz, S. doi  openurl
  Title Evolution in the Social Brain Type Journal Article
  Year 2007 Publication Science Abbreviated Journal Science  
  Volume (down) 317 Issue 5843 Pages 1344-1347  
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  Abstract The evolution of unusually large brains in some groups of animals, notably primates, has long been a puzzle. Although early explanations tended to emphasize the brain's role in sensory or technical competence (foraging skills, innovations, and way-finding), the balance of evidence now clearly favors the suggestion that it was the computational demands of living in large, complex societies that selected for large brains. However, recent analyses suggest that it may have been the particular demands of the more intense forms of pairbonding that was the critical factor that triggered this evolutionary development. This may explain why primate sociality seems to be so different from that found in most other birds and mammals: Primate sociality is based on bonded relationships of a kind that are found only in pairbonds in other taxa.  
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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4243  
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Author Shultz, S.; Dunbar, R.I.M. url  doi
openurl 
  Title Both social and ecological factors predict ungulate brain size Type Journal Article
  Year 2006 Publication Proceedings. Biological Sciences / The Royal Society Abbreviated Journal Proc Biol Sci  
  Volume (down) 273 Issue 1583 Pages 207-215  
  Keywords Animals; Artiodactyla/*anatomy & histology/*physiology; Brain/*anatomy & histology/physiology; *Ecosystem; Organ Size; Perissodactyla/*anatomy & histology/*physiology; *Social Behavior  
  Abstract Among mammals, the members of some Orders have relatively large brains. Alternative explanations for this have emphasized either social or ecological selection pressures favouring greater information-processing capacities, including large group size, greater foraging efficiency, higher innovation rates, better invasion success and complex problem solving. However, the focal taxa for these analyses (primates, carnivores and birds) often show both varied ecological competence and social complexity. Here, we focus on the specific relationship between social complexity and brain size in ungulates, a group with relatively simple patterns of resource use, but extremely varied social behaviours. The statistical approach we used, phylogenetic generalized least squares, showed that relative brain size was independently associated with sociality and social complexity as well as with habitat use, while relative neocortex size is associated with social but not ecological factors. A simple index of sociality was a better predictor of both total brain and neocortex size than group size, which may indicate that the cognitive demands of sociality depend on the nature of social relationships as well as the total number of individuals in a group.  
  Address School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK. susanne.shultz@liv.ac.uk  
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  Language English Summary Language Original Title  
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  Series Volume Series Issue Edition  
  ISSN 0962-8452 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:16555789 Approved no  
  Call Number Serial 2098  
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Author Zhou, W.-X.; Sornette, D.; Hill, R.A.; Dunbar, R.I.M. doi  openurl
  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 (down) 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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  ISSN 0962-8452 ISBN Medium  
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  Notes PMID:15734699 Approved no  
  Call Number refbase @ user @ Serial 549  
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Author Stanley, C.R.; Dunbar, R.I.M. url  doi
openurl 
  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 Abbreviated Journal  
  Volume (down) 85 Issue Pages  
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  Call Number Equine Behaviour @ team @ Stanley2013 Serial 6253  
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Author Dunbar, R.I.M.; McAdam, M.R.; O'connell, S. doi  openurl
  Title Mental rehearsal in great apes (Pan troglodytes and Pongo pygmaeus) and children Type Journal Article
  Year 2005 Publication Behavioural Processes Abbreviated Journal Behav. Process.  
  Volume (down) 69 Issue 3 Pages 323-330  
  Keywords Algorithms; Animals; Child; Child, Preschool; Food; Frontal Lobe/anatomy & histology/physiology; Humans; *Imagination; Pan troglodytes; Pongo pygmaeus; Problem Solving/*physiology; Psychomotor Performance/physiology; Reward  
  Abstract The ability to rehearse possible future courses of action in the mind is an important feature of advanced social cognition in humans, and the “social brain” hypothesis implies that it might also be a feature of primate social cognition. We tested two chimpanzees, six orangutans and 63 children aged 3-7 years on a set of four puzzle boxes, half of which were presented with an opportunity to observe the box before being allowed to open it (“prior view”), the others being given without an opportunity to examine the boxes before handling them (“no prior view”). When learning effects are partialled out, puzzle boxes in the “prior view” condition were opened significantly faster than boxes given in the “no prior view” condition by the children, but not by either of the great apes. The three species differ significantly in the speed with which they opened boxes in the “no prior view” condition. The three species' performance on this task was a function of relative frontal lobe volume, suggesting that it may be possible to identify quantitative neuropsychological differences between species.  
  Address Evolutionary Psychology Research Group, School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK. rimd@liv.ac.uk  
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  Language English Summary Language Original Title  
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  Series Volume Series Issue Edition  
  ISSN 0376-6357 ISBN Medium  
  Area Expedition Conference  
  Notes PMID:15896530 Approved no  
  Call Number Serial 2097  
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Author Shi, J.; Dunbar, R.I.M.; Buckland, D.; Miller, D. url  doi
openurl 
  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 Abbreviated Journal  
  Volume (down) 69 Issue Pages  
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  Call Number Equine Behaviour @ team @ Shi2005 Serial 6257  
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Author Kudo, H.; Dunbar, R.I.M. url  doi
openurl 
  Title Neocortex size and social network size in primates Type Journal Article
  Year 2001 Publication Animal Behaviour. Abbreviated Journal Anim. Behav.  
  Volume (down) 62 Issue 4 Pages 711-722  
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  Abstract Primates use social grooming to service coalitions and it has been suggested that these directly affect the fitness of their members by allowing them to reduce the intrinsic costs associated with living in large groups. We tested two hypotheses about the size of grooming cliques that derive from this suggestion: (1) that grooming clique size should correlate with relative neocortex size and (2) that the size of grooming cliques should be proportional to the size of the groups they have to support. Both predictions were confirmed, although we show that, in respect of neocortex size, there are as many as four statistically distinct grades within the primates (including humans). Analysis of the patterns of grooming among males and females suggested that large primate social groups often consist of a set of smaller female subgroups (in some cases, matrilinearly based coalitions) that are linked by individual males. This may be because males insert themselves into the interstices between weakly bonded female subgroups rather than because they actually hold these subunits together.  
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  Series Volume Series Issue Edition  
  ISSN 0003-3472 ISBN Medium  
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  Notes Approved no  
  Call Number Equine Behaviour @ team @ Serial 4726  
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Author Pérez-Barbería, F.J.; Shultz, S.; Dunbar, R.I.M.; Janis, C. doi  openurl
  Title Evidence For Coevolution Of Sociality And Relative Brain Size In Three Orders Of Mammals Type Journal Article
  Year 2007 Publication Evolution Abbreviated Journal  
  Volume (down) 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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  Notes doi: 10.1111/j.1558-5646.2007.00229.x Approved no  
  Call Number Equine Behaviour @ team @ Serial 4781  
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Author Dunbar, R.I.M. url  doi
openurl 
  Title The social brain hypothesis and its implications for social evolution Type Journal Article
  Year 2009 Publication Annals of Human Biology Abbreviated Journal Annals of Human Biology  
  Volume (down) 36 Issue 5 Pages 562-572  
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  Abstract The social brain hypothesis was proposed as an explanation for the fact that primates have unusually large brains for body size compared to all other vertebrates: Primates evolved large brains to manage their unusually complex social systems. Although this proposal has been generalized to all vertebrate taxa as an explanation for brain evolution, recent analyses suggest that the social brain hypothesis takes a very different form in other mammals and birds than it does in anthropoid primates. In primates, there is a quantitative relationship between brain size and social group size (group size is a monotonic function of brain size), presumably because the cognitive demands of sociality place a constraint on the number of individuals that can be maintained in a coherent group. In other mammals and birds, the relationship is a qualitative one: Large brains are associated with categorical differences in mating system, with species that have pairbonded mating systems having the largest brains. It seems that anthropoid primates may have generalized the bonding processes that characterize monogamous pairbonds to other non-reproductive relationships (?friendships?), thereby giving rise to the quantitative relationship between group size and brain size that we find in this taxon. This raises issues about why bonded relationships are cognitively so demanding (and, indeed, raises questions about what a bonded relationship actually is), and when and why primates undertook this change in social style.  
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  Publisher Taylor & Francis Place of Publication Editor  
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  Series Volume Series Issue Edition  
  ISSN 0301-4460 ISBN Medium  
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  Notes doi: 10.1080/03014460902960289 Approved no  
  Call Number Equine Behaviour @ team @ Serial 6546  
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