Evolutionary Origins of Primate Vocal Communication: Diversity, Flexibility, and Complexity of Vocalizations in Basal Primates

Abstract

This chapter explores the importance of vocalizations in basal primates for modeling the evolutionary origins of primate social communication. A rich diversity in acoustic structures and signals, extending into the ultrasonic range, is used to govern various ecological and social challenges in their networks with varying degrees of social cohesiveness. Vocalizations convey information on specific emotions and on species, population, group, kin, and individual identity. Comparisons within the same phylogenetic group put forth the notion that natural selection limits cross-taxa vocal flexibility and favors universals in acoustic structure, whereas sexual and kin selection drive divergence. Bioacoustic research on vocal ontogeny depicted a babbling period with high vocal plasticity and an unexpected capability in adults to adapt their vocalizations to fluctuating background noise. Using a comparative bioacoustic approach, this chapter illuminates extraordinary cross-taxa variation in the acoustic spaces open for signal evolution and reveals that predation risk specifically shapes the acoustic space used. Comparison of vocal repertoire size, taken as an indicator of vocal complexity, reveals wide cross-taxa variation in call types and a striking variation in both solitary-ranging nocturnal and group-living diurnal species. The phylogenetic hypothesis and the social complexity hypothesis cannot fully explain this variation. Altogether, basal primates exhibit unique diversity, complexity, and flexibility of vocalizations for social communication, providing promising new avenues to trace the evolutionary origins of primate communication.