Alternative Pathways for the Evolution of Gesture

From Hand to Mouth: The Origins of Language by Michael C. Corballis (Princeton: Princeton University Press, 2002. 384 pp., $27.95)

AT THE ROSE CENTER for Earth and Space (the old Hayden Planetarium) in New York City, visitors can traverse the Cosmic Pathway, a spiral walkway that graphically depicts the evolution of the universe. ¹ With 13 billion years of evolution represented, the average visitor travels 75 million years with each step. About three- quarters of the way into the journey, posted among striking astronomical images of galaxies and stars as they looked billions of years ago, is a small plaque with a message.

According to this message, had this very same walkway been constructed not at the end of the twentieth century but in 1935, the year the planetarium opened, it would have started only where the plaque is located. A relatively short time ago, in other words, scientists had no inkling that the universe has been evolving for 13 billion years. Rose Center scientists know that future discoveries will almost certainly extend that number. Blank information panels, installed at the pathway's beginning, await new information.

Exiting the Cosmic Pathway on a recent visit, I thought not only about the evolution of the universe but also about the evolution of language. As a rash of recent volumes newly attests (e.g., Calvin and Bickerton 2000; Deacon 1997; Hurford, Studdert-Kennedy, and Knight 1998; King 1999a; Wray 2002), myriad theories exist about the timing and events associated with the origins of language, each tied to a different understanding of what constitutes language (King 1999b) and each thus mapping a different pathway for the evolution of language. Two types of theories predominate in the literature of the last decade.

In the first type, the emphasis is on modern human speech. Language is thought to be uniquely human, whether by those who are indifferent to questions of language evolution or by those who see modern speech as resulting from late or abrupt changes associated only with Homo sapiens. In the second, a gradual evolution of language is envisioned within the hominid lineage. Most often the focus is on neurological and behavioral developments in hominids appearing early in the development of the genus Homo, starting at about 2 million years ago. Given that the hominid line may well have appeared as early as 7 million years ago, the 2-million-year-old date can be interpreted, depending on one's theoretical persuasion, as either relatively ancient (much earlier than the first appearance of Homo sapiens at about 125,000 ²) or relatively recent (quite far along the hominid line's trajectory).

More rarely one finds a third type of theory, marked by an attempt to show that early hominids (those before 2 million years ago), and especially the African great apes, deserve a prominent role in language-origins thinking. The communicational behaviors of modern-day chimpanzees, bonobos, and gorillas are assessed in order to hypothesize about the abilities in place before the evolutionary split between the African great apes and hominids and about those that might have developed soon after.

As these diverse scenarios attest, scientists cannot state with any certainty when in the human evolutionary past language might have originated. This dilemma stems not only from debates about what language is in the first place but also from severe constraints on methodology. No image-producing technology comparable to the Hubble telescope can aid theorists who wish to reconstruct the origins of language. Our available tools are limited to analyzing the skeletal remains and behavioral artifacts associated with our hominid ancestors, to assessing the linguistic capacities of the brains of extinct hominids and other primates, and to interpreting the relationship between the predicted communication systems of the hominids and those of the living primates.

Will future discoveries in any or all of these areas indicate that language has had a much longer evolutionary history than is now considered...