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Department of Anthropology

Academic Staff

Publication details for Prof Robert A. Barton

Lindenfors, P., Nunn, C.L. & Barton, R.A. (2007). Primate brain architecture and selection in relation to sex. BMC Biology 5(20).

Author(s) from Durham

Abstract

Background: Social and competitive demands often differ between the sexes in mammals. These
differing demands should be expected to produce variation in the relative sizes of various brain
structures. Sexual selection on males can be predicted to influence brain components handling
sensory-motor skills that are important for physical competition or neural pathways involving
aggression. Conversely, because female fitness is more closely linked to ecological factors and social
interactions that enable better acquisition of resources, social selection on females should select
for brain components important for navigating social networks. Sexual and social selection acting
on one sex could produce sexual dimorphism in brain structures, which would result in larger
species averages for those same brain structures. Alternatively, sex-specific selection pressures
could produce correlated effects in the other sex, resulting in larger brain structures for both males
and females of a species. Data are presently unavailable for the sex-specific sizes of brain structures
for anthropoid primates, but under either scenario, the effects of sexual and social selection should
leave a detectable signal in average sizes of brain structures for different species.
Results: The degree of male intra-sexual selection was positively correlated with several
structures involved in autonomic functions and sensory-motor skills, and in pathways relating to
aggression and aggression control. The degree of male intra-sexual selection was not correlated
with relative neocortex size, which instead was significantly positively correlated with female social
group size, but negatively correlated with male group size.
Conclusion: Sexual selection on males and social selection on females have exerted different
effects on primate brain architecture. Species with a higher degree of male intra-sexual selection
carry a neural signature of an evolutionary history centered on physical conflicts, but no traces of
increased demands on sociocognitive tasks. Conversely, female sociality is indicated to have driven
the evolution of socio-cognitive skills. Primate brain architecture is therefore likely to be a product
of ecological and species-specific social factors as well as different sex-specific selection pressures.
Our results also highlight the need for acquisition and analysis of sex-specific brain components in
mammals.