The next three chapters explain how language evolved as a communication system for sharing our thoughts and experiences. These are internal to the mind, and in most nonhuman species largely impenetrable, except in limited ways through the growing ingenuity of neuroscience or inferences drawn from behavior. But we humans have invented ways to share our thoughts. That is what language is for, at least in the sense that language is understood as a communication system rather than itself as a mode of thought. Language often involves the sharing of mental travels in time and space and into other people’s minds, and indeed rides on our ability to understand and relate to what others are thinking and feeling. But these mental adventures are not themselves linguistic, although in sharing them we gain much of what it means to be human. Through language we share the stories, real or imaginary, that define our culture, religion, learning, and entertainment.
Chapter 7 develops the idea that expressive language originated not in animal calls but in bodily gesture. This notion has a long and somewhat controversial history, but in my opinion it makes better sense than supposing that language emerged simply through the modification of animal cries. Chapter 8 then considers the question of how voicing was added, and eventually dominated, giving rise to speech. Chapter 9 examines how grammar emerged to shape our manual or vocal outputs into meaningful sequences, through which we can share ideas, experiences, and stories.
Chapter 10 closes the deal.