How can the overall dynamics of linguistic evolution at the species level be estimated, and to what extent do analogous or homologous communication systems exist among other non-human animals?

To answer this question, the project is to carry out meta-analyses on the vocalisations of several species in order to study vocal diversity and flexibility, and to approach the processes of diversification of communication by looking for homologies and analogies between and within species. The approach will integrate innovative technical and statistical analyses to explore the dynamics of animal’s vocal abilities, providing insights into the constraints driving the evolution of animal communication.

The objective is to gather a database comprising multiple vocalisations, each associated with a set of metadata ranging from broad (such as species identity) to more specific attributes, including individual identity, population, and the context of vocal production. We are aiming to work on various different primate species, but also to take a step back and work on other mammals, reptiles or birds.

Using machine-learning and innovative analysis methods, we will extract various  features from vocalisations and use these features for multiple comparative approaches. These methods will include spectrogram-based embeddings, modulation power spectra, Mel-Frequency Cepstral Coefficients (MFCCs), as well as traditional acoustic parameters (e.g., pitch, formants and frequency modulation).

The main aspect of the project will be to use all these methods and analyses to come back to the biological aspect of vocal communication, by comparing feature-based classifications and projections with various biological characteristics, including the acoustic parameters, but also phylogenetic distances between species, differences in social structures, and variations in vocal production and perception mechanisms.

This project is part of the Diversification project of the NCCR Evolving Language.

Understanding how complex vocal communication systems evolve in non-human primates challenges core assumptions about the relationship between social structure and communicative complexity. Most theoretical models attribute the evolution of elaborate communication either to social demands within complex groups or to ecological pressures like predation.

Yet, species like the olive colobus monkeys (Procolobus verus) — cryptic, and living in small, cohesive groups — show surprisingly complex vocal behaviors. When individuals call, they almost always assemble the vocalizations into long, syntactically structured sequences, defined in terms of rule-governed patterns of call production. Investigating how and why such complexity emerges in species that do not fit traditional models offers a critical opportunity to revise and expand existing evolutionary frameworks.

This research not only contributes to our understanding of primate communication but also
provides a comparative foundation for exploring the origins of human language.