During the first two years of human life a common neural substrate underlies the hierarchical organization of elements in the development of speech as well as the capacity to combine objects manually, including tool use. Subsequent cortical differentiation, beginning at age two, creates distinct, relatively modularized capacities for linguistic grammar and more complex combination of objects. An evolutionary homologue of the neural substrate for language production and manual action is hypothesized to have provided a foundation for the evolution of language (...) before the divergence of the hominids and the great apes. Support comes from the discovery of a Broca's area homologue and related neural circuits in contemporary primates. In addition, chimpanzees have an identical constraint on hierarchical complexity in both tool use and symbol combination. Their performance matches that of the two-year-old child who has not yet developed the neural circuits for complex grammar and complex manual combination of objects. (shrink)

This target article presents a plausible evolutionary scenario for the emergence of the neural preconditions for language in the hominid lineage. In pleistocene primate lineages there was a paired evolutionary expansion of frontal and parietal neocortex (through certain well-documented adaptive changes associated with manipulative behaviors) resulting, in ancestral hominids, in an incipient Broca's region and in a configurationally unique junction of the parietal, occipital, and temporal lobes of the brain (the POT). On our view, the development of the POT in (...) our ancestors resulted in the neuroanatomical substrate consistent with the ability for representations in modality-neutral association cortex and, as a result of structure-imposing interaction with Broca's area, the hierarchically structured Evidence from paleoneurology and comparative primate neuroanatomy is used to argue that Homo habilis (2.5–2 million years ago) was the first hominid to have the appropriate gross neuroanatomical configuration to support conceptual structure. We thus suggest that the neural preconditions for language are met in H. habilis. Finally, we advocate a theory of language acquisition that uses conceptual structure as input to the learning procedures, thus bridging the gap between it and language. (shrink)

Wilkins & Wakefield suggest that changes in the hominid brain made it uniquely “preadaptive” for language, yet no precursor functions served as adaptive substrates to the emergence of language. We present contrary evidence that the ability to discriminate and process rapid and complex auditory information is a cross-species function subserving communication processes including, but not limited to, human speech perception. We suggest that auditory temporal processing served as an evolutionary precursor to speech processing and consequent language development in humans.

Three issues are addressed in this commentary. (1) Wilkins & Wakefield are commended for placing the complex behavior they discuss within an evolutionary matrix. (2) They err on a number of points in regard to their treatment of this complex behavior. These involve (a) their emphasis on the evolution of conceptual structure rather than language, (b) their equation of meaning with reference, (c) their minimalist view of learning theory, and (d) their separation of the evolution of speech from that of (...) language. (3) They adopt a framework for neural preconditions that has been clearly discredited on both behavioral and neuroanatomical grounds. Finally, recent research involving modern neuroimaging techniques casts further doubt on the authors' postulated functions for the neural areas they discuss. (shrink)

If POT (parieto-occipital-temporal junction) reorganization came earlier in australopithecines than in Homo, it is likely that the selective pressures were different, and not necessarily directed toward language. The brain endocast evidence for the POT in A. afarensis is actually better than it is for early Homo.

In recent years, multiple researchers working on the evolution of language have put forward the idea that the theoretical framework of usage-based approaches and Construction Grammar is highly suitable for modelling the emergence of human language from pre-linguistic or proto-linguistic communication systems. This also raises the question of whether usage-based and constructionist approaches can be integrated with the analysis of animal communication systems. In this paper, we review possible avenues where usage-based, constructionist approaches can make contact with animal communication research, (...) which in turn also has implications for theories of language evolution. To this end, we first give an overview of key assumptions of usage-based and constructionist approaches before reviewing some key issues in animal communication research through the lens of usage-based, constructionist approaches. Specifically, we will discuss how research on alarm calls, gestural communication and symbol-trained animals can be brought into contact with usage-based, constructionist theorizing. We argue that a constructionist view of animal communication can yield new perspectives on its relation to human language, which in turn has important implications regarding the evolution of language. Importantly, this theoretical approach also generates hypotheses that have the potential of complementing and extending results from the more formalist approaches that often underlie current animal communication research. (shrink)

This commentary criticizes Wilkins & Wakefield's thesis that the neurological precursors of language provide a cognitive Rubicon to linguistically divide human from nonhuman primates. A causal model of their theory is presented, followed by a discussion of the relationship between brain expansion and tool use, Broca's area and the parietaloccipital-temporal junction (POT).

Wilkins & Wakefield assign importance to motor systems but skip from anatomy to cognitive structure with little attention to behavior. Organisms, no matter how sophisticated, that do not behave in accord with what they know will fall by the evolutionary wayside. Facts about behavior can supplement the authors' theory, whose hierarchical structures can accommodate an evolutionary scenario in which a million years or more of functionally varied utterances mainly limited to single words is followed by an explosion of linguistic diversity (...) with the development in the last 50,000 years or so of syntactically organized multiple word utterances. (shrink)

The precise manner in which language serves its communicative function suggests that natural selection, rather than exaptation or reappropriation, played the major role in its evolution. Natural selection is more readily invoked, I suggest, if it is assumed that language originated as a system of manual gestures, and later switched to an oral mode.

This response clarifies the nature of reappropriation and the definition of language. It explicates the relationship between neural systems and language and between homology and evolutionary gradualism. Through a review of ape capacities in the realms of language and tool use, it distinguishes human language acquisition from nonhuman learning. Finally, it suggests the appropriate sorts of evidence on which to base further evolutionary arguments relevant to the origins of language.

Contra Wilkins & Wakefield, we argue that an evolutionarily inspired approach to language must consider different facets of language (i.e., more than syntax and semantics), and must explore the possibility of nonhuman precursors. Several examples are discussed, illustrating the power of the comparative approach in illuminating our understanding of language evolution.

Despite some sound basic assumptions, Wilkins & Wakefield portray a Homo habilis too linguistically sophisticated to fit in with the subsequent fossil record and thereby lose a reasoned explanation for human innovativeness. They err, too, in accepting a single-level model of conceptual structure and in deriving initial linguistic units from calls, a process far more dubious than the derivation of home-sign from naive gesture.

ProbablyHomo habilisis two species not one; similarly for Pan troglodytes. Although amenable to training, in naturePan paniscusmay be a “specialized insular dwarf.” Language is uniquely human, but symbolic behavior and intelligence are widespread among animals with little respect for phylogenetic closeness toHomo sapiens.

Wilkins & Wakefield are clearly right to separate linguistic capacity from communicative ability, if only because other animal species have one without the other. But I question the abruptness of the demarcation they make between a period when hominids evolved enriched conceptual representation for other reasons entirely, and a subsequent later stage when language use became an adaptation.

Inferences made from endocasts of fossil skulls cannot provide information on the function of particular neocortical areas or the subcortical pathways to prefrontal cortex that form part of the neural substrate for speech, syntax, and certain aspects of cognition. The neural bases of syntax cannot be disassociated from “communication.” Manual motor control was probably a preadaptive factor in the evolution of humansyntactic ability, but neurophysiological data on living humans show that speech motor control and syntax are more closely linked. The (...) evolution of fully modern speech occurred fairly recently; thoughHomo habilismay have had some degree of speech and syntactic ability, it was not fully modern. Stone tools are uncertain indices of language or cognition. (shrink)

Wilkins & Wakefield's intriguing model of language evolution is deficient in evidence of human uniqueness in metaphorical matching, amodal representation, reference, conceptual structure, hierarchical organization, linguistic comprehension, sign use, laterality, and handedness. Primates show communicative reference, laterality, and handedness, and apes in particular show hierarchical organization, conceptual structure, cross-modal abilities, sign use, and displaced reference.

Wilkins and Wakefield's hypothesis that language is fundamentally a cognitive rather than cominunicational adaptation is reasonable, but there are flaws in their anatomical and fossil evidence. Their analysis of reorganization also needs clarification. Finally, the origin of language ability must have occurred with australopithecine rather than habiline adaptations on entry into the novel hominid adaptive zone.

Wilkins & Wakefield's identification of anatomical features in the Koobi Fora endocast, which may be thought to carry some functional significance in relation to organization for language, raises fundamental problems of method: attention is drawn to some limitations of the evidence, of endocasts and of the neuroanatomical map used to interpret them.

Hominid-like morphology in habiline cranial endocasts does not necessarily imply the presence of language capacity. The cortical zone in question is not associated exclusively with language in humans, and its emergence in habilines might indicate the evolution of other cognitive functions special to humans that were preconditions for the later evolution of language.

Representation must be prior to communication in evolution. Wilkins & Wakefield's target article gives the impression that communicative pressures play a secondary role. We suggest that their evolutionary precursor is compatible with protolanguage rather than language itself. The difference between these two communicative systems should not be underestimated: only the former can be trivially reappropriated from a representational system.

Several claims made by Wilkins & Wakefield require qualification. First, the proposed delineation of the parietal-occipital-temporal junction (POT) is overly restrictive. Second, focusing exclusively on the evolutionary importance of manual manipulation oversimplifies interacting evolutionary preconditions for language. Finally, Wilkins and Wakefield's perspective adheres to a homocentric, formal, linguistic definition of language instead of viewing language as a multimodal sensory enhancement system unique to each species.

Preadaptation for language is an unnecessary assumption because intermediate stages of linguistic ability are possible and adaptive. Language could have evolved through gradual selection from structures exhibiting few features associated with modern structures. Without physical evidence pertaining to language ability in prehabilis hominids, it remains possible that selective pressures for language use preceded and necessitated modern neurolinguistic structures.

Understanding how conceptual structures inform stone tool production and use would help us resolve the issue of a pongid-hominid dichotomy in brain organisation and cognitive ability. Evidence from ideational apraxia suggests that the planning of linguistic and manipulative behaviours is not colocalized in homologous circuits. An alternative account in terms of the evolutionary expansion of the whole prefrontal-premotor area may be more plausible.

This commentary confronts one of the central tenets advanced in Wilkins & Wakefield's target article: By adopting a very narrow perspective on language, the authors have effectively limited discussion of earlier linguistic capabilities thought to be at least facilitative of, if not prerequisite to language defined as a An alternative conceptualization for describing semiogenesis is offered.

Wilkins & Wakefield fall short of solving the language origin puzzle because they underestimate the cognitive and linguistic capacities of great apes. A focus on ape capacities leads to the recognition of varied levels of cognition and language and to a gradualistic model of language emergence in which early hominid language skills exceed those of the apes but fall far short of those of modern humans or later fossil hominid groups.