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I recently read through Marc Hauser et al., "The Mystery of Language Evolution", Frontiers in Psychology 2014, which expresses a strongly skeptical view on every aspect of the topic, including this one:

[S]tudies of nonhuman animals provide virtually no relevant parallels to human linguistic communication, and none to the underlying biological capacity.

By "underlying biological capacity" they mean something rather narrow, which they call "the language phenotype":

As we and many other language scientists see it, the core competence for language is a biological capacity shared by all humans and distinguished by the central feature of discrete infinity—the capacity for unbounded composition of various linguistic objects into complex structures. These structures are generated by a recursive procedure that mediates the mapping between speech- or sign-based forms and meanings, including semantics of words and sentences and how they are situated and interpreted in discourse. This approach distinguishes the biological capacity for language from its many possible functions, such as communication or internal thought.

This definition leaves out the many aspects of human anatomy and physiology that are relevant to speech and language, and are both shared with other animals and also evolutionarily adapted to make human speech and language work better. There's an old debate about whether it makes sense to ignore all of these other capabilities: for some play-by-play, see "JP versus FHC+CHF versus PJ versus HCF", 8/25/2005.

But there's an even older proposal, which is consistent with Hauser et al.'s view of the language phenotype while explicitly and strongly disagreeing with the claim that there are no relevant nonhuman parallels.

This idea is eloquently presented in a work that I recently re-read in preparation for a forthcoming workshop on "Prosodic Grammar" — Karl Lashley's 1951 chapter "The Problem of Serial Order in Behavior". If you've never read it, do yourself a favor and read it now. To whet your appetite, here are a few relevant quotations:

The study of comparative grammar is not the most direct approach to the physiology of the cerebral cortex, yet Fournié has written, “Speech is the only window through which the physiologist can view the cerebral life.” Certainly language presents in a most striking form the integrative functions that are characteristic of the cerebral cortex and that reach their highest development in human thought processes.

Temporal integration is not found exclusively in language; the coordination of leg movements in insects, the song of birds, the control of trotting and pacing in a gaited horse, the rat running the maze, the architect designing a house, and the carpenter sawing a board present a problem of sequences of action which cannot be explained in terms of successions of external stimuli.

Or later:

[I]t is certain that any theory of grammatical form which ascribes it to direct associative linkage of the words of the sentence overlooks the essential structure of speech. The individual items of the temporal series do not in themselves have a temporal “valence” in their associative connections with other elements. The order is imposed by some other agent.

This is true not only of language, but of all skilled movements or successions of movement.

And finally:

I have devoted so much time to discussion of the problem of syntax, not only because language is one of the most important products of human cerebral action, but also because the problems raised by the organization of language seem to me to be characteristic of almost all other cerebral activity. There is a series of hierarchies of organization […] Not only speech, but all skilled acts seem to involve the same problems of serial ordering, even down to the temporal coordination of muscular contractions in such a movement as reaching and grasping. Analysis of the nervous mechanisms underlying order in the more primitive acts may contribute ultimately to the solution even of the physiology of logic. […]

This is the essential problem of serial order: the existence of generalized schemata of action which determine the sequence of specific acts, acts which in themselves or in their associations seem to have no temporal valence.

In evolutionary terms, Lashley is suggesting that a key innovation, maybe THE key innovation, was learning to map structured ideas onto structured action plans (= "generalized schemata of action"); and that the "series of hierarchies of organization" that are characteristic of human syntax were originally borrowed from structures present in "not only speech, but all skilled acts".

We've learned a lot since 1951 about motor control and motor planning, and also about how speech and language work; and in my opinion, the progress makes Lashley's suggestion look even more plausible. Two random relevant links, out of hundreds:

Michael Studdert-Kennedy and Louis Goldstein, "Launching language: The gestural origin of discrete infinity", Studies in the Evolution of Language, 2003

Marc Schmidt et al., “Breathing and Vocal Control: The Respiratory System as both a Driver and Target of Telencephalic Vocal Motor Circuits in Songbirds”. J. Exp. Physiology 2011.

Neither Lashley's chapter, nor either of those two particular pieces of work, nor anything from the several other areas of related research, is cited or discussed in the Hauser et al. article. The lack of attention to the Studdert-Kennedy and Goldstein article is especially odd, since it was published in a volume "Studies in the Evolution of Language", and puts the "gestural origin of discrete infinity" up front in the title.

Hauser et al. do cite Eric Lenneberg's 1967 book The Biological Foundations of Language. One of the best parts of my undergraduate education was a seminar that Lenneberg taught on the topic of the book as he was writing it — and I recall Lashley-on-serial order as a central focus of that course.

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