Archived Abstracts
Co-evolution of facial expression and social tolerance in macaques
Authors: Seth D. Dobson
What is the function of increased communicative complexity? Signals convey information to receivers. But this observation does not tell us why species should evolve to have more complex communication systems. I suggest that social uncertainty creates a need for more options when negotiating the outcome of behavioral interactions. If interactions are constrained by strict social roles, then fewer signals will suffice. However, if there is flexibility in the social system, then natural selection should favor individuals that produce a wider range of social signals. To test this hypothesis, I examined the relationship between the degree of social uncertainty and the number of facial displays in the repertoire of 11 species of macaque using previously published data. As predicted, species characterized by less rigid social systems tended to have a wider range of facial displays at their disposal than species with strong societal constraints. These results suggest that function of communicative complexity is to reduce the social uncertainty found in more tolerant societies.
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