Evolution of Speech and Its Acquisition

Abstract

Much is known about the evolution of speech. Fossil evidence points to modern adaptations for speech appearing between 1.5 million and 500,000 years ago. Studies of vocal behavior in apes show the ability to use combinatorial vocalizations in some species (but not chimpanzees) and some cultural influence on vocalizations, but little ability for vocal imitation. For modern speech, the comparison of many languages shows that speech can become extremely complex, but that it can also be astonishingly simple. Finally, the way in which infants acquire speech is becoming increasingly clear. We therefore know about the starting point of the evolution of speech, its end point and some steps in between. Much less is known about the exact scenario and the dynamics of the evolution of the acquisition of speech. As it involves co-evolution between culturally transmitted sounds and genetic evolution, the dynamics are complex. Computer models are therefore ideal for studying these dynamics. This paper presents a computer model of the co-evolution between a repertoire of speech sounds and a population of learners that can either represent a lexicon holistically or combinatorially. It shows that cultural influences can change the dynamics of the transition between a population of holistic and combinatorial learners.