IMPRS DOCTORAL DEFENCE: Koen de Reus

Open to the public for in-person attendance as well as via live-stream.
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Abstract

How and why did language evolve in humans, and what can we learn from communication in other animals? Language is a uniquely powerful tool for social interaction and is often considered to set humans apart from the rest of the animal kingdom. Yet, many species have evolved complex communication systems that share features with human language. The discovery in the 1980s that harbour seals can imitate human speech highlighted their potential as a comparative model for language evolution. However, a systematic understanding of the similarities between human language and harbour seal communication has so far been lacking. This thesis provides an interdisciplinary investigation of vocal communication in harbour seals, focusing on vocal flexibility, vocal development, social accommodation, and turn-taking. All empirical studies were conducted using non-invasive bioacoustic methods, including audio recordings and playback experiments, as well as morphometric measurements. In addition, the thesis presents a qualitative cross-species review of rhythmic patterns in social interactions across mammals, birds, anurans, and insects. Together, these findings demonstrate that harbour seal communication shares key features with both human language and other animal systems, supporting its value as a comparative model. More broadly, this work illustrates how comparative approaches can shed light on the biological and social factors shaping the evolution of communication.