Neocortex size as a constraint on group size in primates

doi:10.1016/0047-2484(92)90081-J

Journal of Human Evolution

Volume 22, Issue 6, June 1992, Pages 469-493

https://doi.org/10.1016/0047-2484(92)90081-J Get rights and content

Abstract

Two general kinds of theory (one ecological and one social) have been advanced to explain the fact that primates have larger brains and greater congnitive abilities than other animals. Data on neocortex volume, group size and a number of behavioural ecology variables are used to test between the various theories. Group size is found to be a function of relative neocortical volume, but the ecological variables are not. This is interpreted as evidence in favour of the social intellect theory and against the ecological theories. It is suggested that the number of neocortical neurons limits the organism's information-processing capacity and that this then limits the number of relationships that an individual can monitor simultaneously. When a group's size exceeds this limit, it becomes unstable and begins to fragment. This then places an upper limit on the size of groups which any given species can maintain as cohesive social units through time. The data suggest that the information overload occurs in terms of the structure of relationships within tightly bonded grooming cliques rather than in terms of the total number of dyads within the group as a whole that an individual has to monitor. It thus appears that, among primates, large groups are created by welding together sets of smaller grooming cliques. One implication of these results is that, since the actual group size will be determined by the ecological characteristics of the habitat in any given case, species will only be able to invade habitats that require larger groups than their current limit if they evolve larger neocortices.

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Neocortex size as a constraint on group size in primates

Abstract

J. hum. Evol

Anim. Behav

Ethol. Sociobiol

Anim. Behav

Anim. Behav

Brain Res

J. hum. Evol

Anim. Behav

Ecological and social determinants of cercopithecine mating patterns

Relative brain size in monkeys and prosimians

Am. J. phys. Anthrop

Relative size of the anterior thalamic nuclei differentiates anthropoids by social system

Brain Behav. Sci

Brain organisation and taxonomic relationships in Insectivora and Primates

Mental map in wild chimpanzees: an analysis of hammer transports for nut cracking

Primates

Solitary and gregarious prosimians: evolution of social structures in primates

Evolution of lorises and lemurs

Nature (Lond.)

Patterns of group splitting within matrilineal kinship groups: a study of social group structure in Macaca mulatta (Cercopithecidae: Primates)

Behav. Ecol. Sociobiol

The quantitative assessment of phylogenetic constraints in comparative analyses: sexual dimorphism in body weight among primates

Evolution

Sociality in a nocturnal “solitary” prosimian: Galago crassicaudatus

Int. J. Primatol

Primates, brains and ecology

J. Zool. Lond

Group fission in blue monkeys of the Kakamega Forest, Kenya

Folia primat

Problems of ontogeny and phylogeny in brain-size evolution

Int. J. Primat

Fallacies of progression in theories of brain-size evolution

Int. J. Primat

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Social systems as optimal strategy sets: the costs and benefits of sociality

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J. Zool. Lond

Functional significance of social grooming in primates

Folia primat

Spatial autocorrelation, phylogenetic constraints and the causes of sexual dimorphism in primates

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Primates

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Am. J. Primat

L'ecologie du talapoin du Gabon

Terre Vie

Cognition, brain size and the extraction of embedded food resources

New perspectives on instincts and intelligence: brain size and the emergence of hierarchical mental constructional skills

Carnivore brain size, behavioural ecology and phylogeny

J. Mammal

Tamarins and marmosets: communal care of offspring

Alliances in contests and social intelligence

Sociality and competition in primates and non-primates

Lifehistory variation in primates

Evolution

Comparisons between taxa and adaptive trends

Sexual dimorphism in primate teeth

J. Zool. Lond