Preface to the Featured Reviews: new studies for understanding the evolutionary process of human speech

From 2015 to 2017 I ran a research project entitled ‘International Collaboration for Understanding the Evolutionary Process of Human Speech’ with funding from the Supporting Program for InteRaction-based Initiative Team Studies (SPIRITS) program of Kyoto University. The project helped enhance a long-term international collaboration between the Department of Cognitive Biology, University of Vienna, Austria and the Primate Research Institute of Kyoto University. Research was based on the comparative anatomy, physiology, and cognition of vocalizations in non-human primates, to improve our understanding of the primate origins and evolutionary processes of human speech.

Humans have a physical ability to produces a series of many distinct voice sounds, including vowels and consonants, even in a very short time, such as a single exhalation. This distinctive acoustic and physiological feature of speech is not found in any vocalizations of terrestrial mammals, including non-human primates. There is no doubt that the speech arose in hominin evolution after the last common ancestor between humans and chimpanzees. Although fossils provide hard evidence for the evolutionary process in many aspects of human nature, unfortunately the faculties of speech and vocalization left very limited fossil evidence: the vocal apparatus producing speech is almost exclusively made up of soft tissues, including muscles, ligaments, cartilages, and connective tissues. One of the alternative approaches to address the question of how speech might evolved is to use comparative biology between humans and their evolutionary neighbors, the non-human primates.

Over the two years, we invited many affiliated scholars, who were using cutting-edge techniques and creative ideas to pursue novel multidisciplinary approaches to break through the technical limitations that have prevented the collection of empirical evidence of the vocal anatomy and physiology of non-human primates. Our international collaboration was successful in enhancing our knowledge and expanding our perspective. We held an international symposium entitled ‘Biology and Evolution of Speech’ at the Science Seminar House, Kyoto University, Kyoto, on 23 February 2017, which was additionally supported by the Subcommittee of Evolutionary Anthropology, the Anthropological Society of Nippon, Japan. This Featured Reviews section of Anthropological Science was planned to gather together selected papers presented at the symposium regarding recent advances and foresights in the vocal anatomy and physiology of non-human primates. I hope these reviews stimulate further development of the evolutionary physiology of the voice in non-human primates and mammals.