Consequently, there has been considerable interest in efforts over the last several decades to train various types of primates to communicate with humans using sign language or other means, like symbols on a keyboard. Presumably, the argument is that if modern primates can be shown to possess an ability to use human-like language, this would provide credibility for the argument that human language began with non-vocal means like those used by these primates. Moreover, this might also demonstrate that language is not such a uniquely human characteristic, as long thought.
Among these experimental efforts to teach primates how to "talk." one of the most publicized "success stories" has been that of a male bonobo chimpanzee named Kanzi (pictured above). According to Brad Harrub, Bert Thompson, and Dave Miller in their article "The Origin of Language and Communication" (available from AnswersinGenesis.org):
Kanzi was born 28 October 1990, and began his long journey to "speak" as a result of the training provided for his mother, Matata, via a "talking'" keyboard. Matata never did master the keyboard, but Kanzi did. Through many years of intense training and close social contact with humans, this remarkable animal attained the language capabilities of an average two-year-old human. By age ten, he had a vocabulary (via the keyboard) of some two hundred words. In fact, Kanzi was able to go beyond the mere parroting or "aping" of humans; he actually could communicate his wants and needs, express feelings, and use tools.
Such impressive skills would appear to prove that primates have a capacity for language. Yet, as John Skoyles and Dorion Sagan point out in their book Up from Dragons (as quoted by Harrub, Thompson, and Miller): "Kanzi shows that while chimps may have the potential to learn language, they require a 'gifted' environment to do so. Kanzi was surrounded by intelligent apes with Ph.D.s [i.e., human researchers] who spoke to him and gave him a stream of rich interactions. They gave Kanzi's brain a world in which it could play at developing its ability to communicate...Therefore, Kanzi's skill lies in the environment which helped shape it" (p. 215-216). That is to say, the environment in which Kanzi developed his unusual linguistic abilities is hardly typical for a chimpanzee or other primate. Indeed, as Jeff Roesler Stebbins argues in his article "The Evolution of Evolutionary Lingustics," (Colorado Research in Linguistics, June 2007), "experiments in which primates are trained to use sign languages [or, presumably, other kinds of non-vocal forms of communication]...are conducted under such stringently controlled situations that we learn very little about primates in the wild."
Furthermore, it appears that the "language" produced by the primates in experiments like those involving Kanzi lacks many of the hallmarks of human language. For example, according to Stebbins, the primates in these experiments, even after years of training , remain incapable of producing (or understanding) negation, verb tenses, questions, commands, or recursion (the embedding of phrases within phrases, like "the old man whom I met in the park yesterday who is a World War II veteran"). In fact, as Stebbins notes, "years of research has shown that, unless they receive extensive training (and most, even if they do), primates...do not use gestures referentially to represent anything not present." In other words, the primates in these experiments are unable to use language to refer to something that is not actually present, something humans do rather frequently. In short, as Stebbins says, "so far, comparisons of human language and primate gestures (whether vocal or non-vocal) appear to teach us more about how we differ than about what we have in common."
Another matter to consider is that human language consists mainly of vocalizations, not non-vocal gestures. Even if it could be shown that it would have been possible for prehistoric primates to have used gestures as a form of language, what is still unexplained is how human language evolved from being non-vocal to primarily vocal in nature. The crux of the problem is that, as mentioned above, primates lack the vocal apparatus humans have. As Stebbins points out, "only the human larynx ["voice box"] is low enough (and the human pharynx relatively long enough) to produce the phonology [sound system] of human language ." The larynx is located higher in primates than in humans and the pharynx is shorter in primates than in humans. Consequently, primates are unable to duplicate the sounds of human speech. Ironically, the animals that come closest to humans in vocal ability are birds and some aquatic mammals, yet these are not seen as sharing common ancestry with humans in the way primates are.
To conclude, it would appear that experiments in teaching chimpanzees and apes how to "speak" using non-vocal means fail to provide sufficient evidence for an evolutionary explanation of the origins of human language. Thus, the genesis of language would appear to be still shrouded in mystery, unless, as I have suggested in an earlier post ("Words and the Word"), we assume that human language is a gift from a Creator. Questions about the origin and nature of human language are of cosiderable interest to me, so I imagine I will have more to say on these topics in the future.