This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Biologists, zoologists and psychologists have been trying to trace the origins of human language for centuries. One well-known theory, known as the social brain hypothesis, suggests that increasingly complex social lives prompted primates to evolve increasingly larger brains, which in turn led to increasingly advanced communication skills.
Different primates can produce varying collections of sounds or calls, also referred to as vocal repertoires. While many past studies have explored how primates communicate, the factors that shaped observed differences in primate vocal repertoires over the course of evolution have not yet been clearly elucidated. Lameira, a researcher at the University of Warwick's ApeTank, recently analyzed one of the most comprehensive datasets of primate vocal repertoires compiled to date to determine whether the vocal diversity of primates could be better explained by their social lives or by physical factors.
His paper, published in Biology Letters, challenges the idea that larger primates with bigger brains have richer vocal repertoires. Instead, it suggests that a combination of body size and habitat shaped the evolution of their communication strategies. "This study was very much inspired by a seminal study by McComb and Semple, also published in Biology Letters about 20 years ago, which cemented the notion that social and vocal complexity and evolution go hand in hand," Lameira told Phys.org.
"While the study potentiated all information that was available then, there have been great strides made in the last 20 years in new descriptions of primate vocal repertoires across species." Recent studies suggest that ecology played a more decisive role in the evolution of language than originally predicted. In addition, they showed that more social members of an animal group do not always communicate better or in richer ways than less social ones. "My objective was to reassess the role of sociality with a much larger, newer dataset while controlling for physical and ecological effects," said Lameira.
"Given my interest in the topic, I've followed closely all new developments regarding novel descriptions of primate vocal repertoires and have collated these studies over the years. This was then supplemented with a comprehensive and extensive web search." The dataset analyzed by Lameira includes the vocal repertoires of 77 different primate species. The researcher examined the size of these species' vocal repertoires (i.e., how many distinct vocal signals or calls they can produce), their average body and brain sizes, the typical size of their social groups and the habitats they inhabit.
"I compared the distribution of vocal repertoire size across the primate order with published databases of primate brain sizes, social group sizes and published descriptions of each species' weight and ecological lifestyle: ground-dwelling, arboreal or mixed," Lameira explained. "This analysis allowed me to control for the phylogenetic distance between species—that is, how closely or distantly related they are to one another—and then pinpoint which factors best predict and presumably drive a species' vocal repertoire size." The statistical analyses carried out by Lameira showed that the average brain size and social group size of each considered primate species did not predict the richness of its vocal calls. These findings clash with the social brain hypothesis, as they indicate that having a larger brain and being more social does not translate into a larger vocal repertoire.
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