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Dunbar, R.I.M. |
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Title |
Observations on the ecology and social organization of the green monkey,Cercopithecus sabaeus, in Senegal |
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1974 |
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Primates |
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Primates |
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15 |
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4 |
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341-350 |
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The green monkey,Cercopithecus sabaeus, has not been studied in its natural habitat in West Africa. This paper reports observations made during a 3-month study in Senegal. Green monkeys live in multimale groups averaging some 12 individuals. Information is given on home range size, use of habitat, daily activity patterns, diet and birth seasonality. Social organization is discussed and data are given on the relationships between age-sex classes, aggression and leadership. Inter-group relations are discussed and it is suggested that groups defend their ranges as territories. The ecology and social organization of green monkeys is compared with that of populations ofC. aethiops studied in East Africa and they are found to be similar. |
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2062 |
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Kudo, H.; Dunbar, R.I.M. |
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Title |
Neocortex size and social network size in primates |
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Year |
2001 |
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Animal Behaviour. |
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Anim. Behav. |
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62 |
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4 |
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711-722 |
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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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0003-3472 |
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Equine Behaviour @ team @ |
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4726 |
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Author |
Zhou, W.-X.; Sornette, D.; Hill, R.A.; Dunbar, R.I.M. |
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Title |
Discrete hierarchical organization of social group sizes |
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Journal Article |
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Year |
2005 |
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Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
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Volume |
272 |
Issue |
1561 |
Pages |
439-444 |
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Anthropology, Cultural; *Group Structure; Humans; *Models, Biological; *Social Behavior; *Social Environment |
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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. |
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State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237, China |
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0962-8452 |
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PMID:15734699 |
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refbase @ user @ |
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549 |
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Author |
Dunbar, R.I.M.; McAdam, M.R.; O'connell, S. |
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Title |
Mental rehearsal in great apes (Pan troglodytes and Pongo pygmaeus) and children |
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Journal Article |
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Year |
2005 |
Publication |
Behavioural Processes |
Abbreviated Journal |
Behav. Process. |
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69 |
Issue |
3 |
Pages |
323-330 |
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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 |
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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. |
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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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0376-6357 |
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PMID:15896530 |
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no |
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Call Number |
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Serial |
2097 |
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Author |
O'Connell, S.; Dunbar, R.I.M. |
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Title |
The perception of causality in chimpanzees (Pan spp.) |
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Journal Article |
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Year |
2005 |
Publication |
Animal Cognition |
Abbreviated Journal |
Anim. Cogn. |
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Volume |
8 |
Issue |
1 |
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60-66 |
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Animals; *Association Learning; Awareness; *Concept Formation; Female; *Habituation, Psychophysiologic; Male; Pan paniscus/*psychology; Pan troglodytes/*psychology; Perception |
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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. |
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Evolutionary Psychology Research Group, School of Biological Sciences, Biosciences Building, University of Liverpool, Liverpool, L69 7ZB, UK |
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1435-9448 |
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PMID:15322943 |
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Equine Behaviour @ team @ |
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2514 |
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Author |
Shi, J.; Dunbar, R.I.M.; Buckland, D.; Miller, D. |
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Dynamics of grouping patterns and social segregation in feral goats (Capra hircus) on the Isle of Rum, NW Scotland |
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Journal Article |
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2005 |
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Mammalia |
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69 |
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Equine Behaviour @ team @ Shi2005 |
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6257 |
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Shultz, S.; Dunbar, R.I.M. |
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Both social and ecological factors predict ungulate brain size |
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Year |
2006 |
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Proceedings. Biological Sciences / The Royal Society |
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Proc Biol Sci |
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273 |
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1583 |
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207-215 |
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Animals; Artiodactyla/*anatomy & histology/*physiology; Brain/*anatomy & histology/physiology; *Ecosystem; Organ Size; Perissodactyla/*anatomy & histology/*physiology; *Social Behavior |
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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. |
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School of Biological Sciences, University of Liverpool, Biosciences Building, Crown Street, Liverpool L69 7ZB, UK. susanne.shultz@liv.ac.uk |
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0962-8452 |
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PMID:16555789 |
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2098 |
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Dunbar, R.I.M.; Shultz, S. |
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Title |
Understanding primate brain evolution |
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2007 |
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Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |
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Philos Trans R Soc Lond B Biol Sci |
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362 |
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1480 |
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649-658 |
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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. |
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British Academy Centenary Research Project, School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, UK. rimd@liv.ac.uk |
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0962-8436 |
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PMID:17301028 |
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2099 |
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Dunbar, R.I.M. |
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Title |
Male and female brain evolution is subject to contrasting selection pressures in primates |
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Journal Article |
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2007 |
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BMC Biology |
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BMC Biol |
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5 |
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21 |
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Animals; *Brain/physiology; *Evolution; Female; Humans; Male; *Selection (Genetics); *Sex Characteristics |
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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. |
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British Academy Centenary Research Project, School of Biological Sciences, University of Liverpool, Liverpool, UK. rimd@liv.ac.uk |
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1741-7007 |
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PMID:17493267 |
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2100 |
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Dunbar, R.I.M.; Shultz, S. |
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Title |
Evolution in the Social Brain |
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2007 |
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Science |
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Science |
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317 |
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5843 |
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1344-1347 |
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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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Equine Behaviour @ team @ |
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4243 |
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