WHY APE-HUMAN SIMILARITIES AND LEARNING MECHANISMS ARE IMPORTANT: A DEVELOPMENTAL AND CLADISTIC APPROACH TO THE EVOLUTION OF LANGUAGE

For the last thirty years species comparative approaches to the study of the evolution of language have shown a strong bias toward uncovering differences between apes and humans in their symbolic and communicative capacities. Flying in the face of the well established fact that chimpanzees and humans share 99% of their genes, researchers and scholars seem motivated to emphasize the uniqueness of human language at the expense of understanding its origins and foundations in primate communication. Another tendency in the field is to assume that only spontaneously manifest symbolic capacities are of interest and to ignore learning mechanisms that rely on social or nonlinguistic stimuli. In order to counter these trends, I will be presenting an alternative theoretical and methodological framework.

Its first tenet is that cladistic analysis (comparative study of species descended from a common ancestor) is an important tool for understanding the primate foundation of human language and communication. This is because similarity of a characteristic across a clade (a phyologenetically related group of species with a common ancestor) indicates that it is likely to be an ancestral trait that is part of the genetic heritage of all members of the clade. Therefore, comparing behaviors across a clade is a research strategy that can uncover ancestral behavioral capabilities that served as the foundation for modern capabilities – in this case for language and communication. This theoretically based methodological point is particularly important because language, like other behavioral capabilities, does not leave fossils.

The second tenet is that earlier stages of development are more similar among members of a clade than are later stages of development. Therefore, comparing behaviors in very young members of each species across the clade is most likely to uncover evolutionary foundations for a particular system, in this case, language and communication.

Third, later capabilities build on earlier ones in both ontogeny and phylogeny. Therefore, the analysis of developmental transitions from one stage to another is useful in understanding both ontogeny and phylogeny. We therefore will examine behavioral development – in this case the development of language and communication – over time in each species,. But our analysis does not focus on time or age per se; instead it emphasizes the transitional learning mechanisms that drive symbolic and communicative development from one level to the next.

Fourth, earlier stages of development are more universal within a species than are later stages of development. This is because both ontogeny and phylogeny build on what is already there rather than erasing it, so both speciation and individual differences in development tend to be found in later rather than earlier stages of development, Therefore, sample selection and large sample size within each species is less important than when studying older members of a species: cross-species similarities early in life are likely to be robust across a wide range of species members.

Fifth, language evolved for communication. Therefore, the social stimuli provided by conversation should provide important developmental learning mechanisms.

Sixth, language evolved out of nonlinguistic behaviors and capacities. Therefore, nonlinguistic communication, specifically gesture, is a good candidate for a developmental learning mechanism.

These principles have animated a series of cross-species comparative studies that demonstrate common transitional mechanisms in the early development of symbolic communication and representation across the clade consisting of bonobo, chimpanzee, and human. According to the principle of cladistic analysis, these transitional mechanisms then become good candidates for mechanisms that lie at the very foundation of language evolution. While we rely heavily on a small number of members of each species – mainly because highly rare symbol-enculturated apes are at the heart of the research designs – the focus on early development means that our findings may not only constitute an existence proof, but also index species-typical capabilities held in common by all three species in the clade. We will provide evidence that three kinds of transitional mechanisms - gesture, dialogue, and social scaffolding - are utilized across the clade in the ontogeny of symbolic and communicative capacities. More specifically, we will show how, in bonobo, chimpanzee, and child, each of the three mechanisms leads to a similar developmental progression in symbolic representation or communication. We see these commonalities as a foundation from which human language, communication, and representation evolved after the phylogenetic split of the three species five million years ago. Rather than trying to figure out where human language went in its evolution, we are trying to figure out where it started. Learning where it started can give us critical information about the evolution of its most basic and robust characteristics. Learning where it started is also essential for understanding where human language has gone in the last five million years. Thus, it is not an either-or situation. Instead, the study of cross-species similarities complements and provides a context for the study of cross-species differences in language evolution.

Note from Publisher: This article contains the abstract only.