Thanks for taking up our paper in your blog (Nóbrega and Miyagawa, 2015, Frontiers in Psychology). We are glad that you appreciate our arguments against the gradualist approach to language evolution. There are two things that don't come out in your blog that we want to note.
First, our arguments against the gradualist view are predicted by the Integration Hypothesis, which Miyagawa proposed with colleagues in earlier Frontiers articles (Miyagawa et al. 2013, 2014). The gradualists such as Progovac and Jackendoff claim that compounds such as doghouse and daredevil are living fossils of an earlier stage in language, which they call protolanguage. The reason is that the two "words" are combined without structure, due to the fact that these compounds (i) have varied semantic interpretations (NN compounds), and (ii) are unproductive and not recursive (VN compounds). We argued that if one looks beyond these few examples, we find plenty of similar compounds that are fully productive and recursive, such as those in Romance and Bantu. These productive forms show that the members that make up the compound are not bare roots, but are "words" in the sense that they are associated with grammatical features of category and sometimes even case.
This is precisely what the Integration Hypothesis (IH) predicts. IH proposes that the structure found in modern language arose from the integration of two pre-adapted systems. One is the Lexical system, found in monkeys, for example. The defining characteristic of the L-system is that it is composed of isolated symbols, verbal or gestural, that have some reference in the real world. The symbols do not combine. The other is the Expressive system found in birdsong. The E-system is a series of well-defined, finite state song patterns, each song without specific meaning. For instance, the nightingale may sing up to 200 different songs to express a limited range of intentions such as the desire to mate. The E-system is akin to human language grammatical features. These are the two major systems found in nature that underlie communication. IH proposes that these two systems integrated uniquely in humans to give rise to human language.
Based on the nature of these two systems, IH predicts that the members of the L-system do not combine directly, since that is a defining characteristic of the L-system. E must mediate any such combination. This is why the IH predicts that there can't be compounds of the form L-L, but instead, IH predicts L-E-L. Such an assumption bears a close relation to how human language roots are ontologically defined, as feature-less syntactic objects. Once roots are feature-less they are invisible to the generative system, thus there is no motivation a priori to assume that syntax merges two bare roots, that is, two syntactically invisible objects.
The second point is that the L-system is related to such verbal behavior as the alarm calls of Vervet monkeys. We focus on the fact that these calls are isolated symbols, each with reference to something in the real world (thus, they are closer to concepts rather than to full-blown propositions). You question the correlation by noting that while the elements in a monkey's alarm calls appear purely to be referential, words in human language are more complex, a point also Chomsky makes. We also accept this difference, but separate from this, roots and alarm calls share the property, if we are right, that they are isolated elements that do not directly combine. This is the property we key in on in drawing a correlation between roots and alarm calls as belonging to the L-system. In addition to the referential aspect of alarm calls, there is another important question to solve: what paved the way to the emergence of the open-vocabulary stored in our long-term memory, since alarm calls are very restricted? Perhaps what you’ve mentioned as “something ‘special’ about lexicalization”, that is, the effect that Merge had on the pre-existing L-system, may have played a role in the characterization of human language roots, allowing the proliferation of a great number of roots in modern language. Nevertheless, we will only get a satisfactory answer to this question when we have a better understanding of the nature of human language roots.
Finally, you might be interested to know that Nature just put up a program on primate communication and human language on Nature Podcast in which Chomsky and Miyagawa are the linguists interviewed.
Also, BBC will be broadcasting a Radio 4 program on May 11 (GBST) about evolution of language that will in part take up the Integration Hypothesis (or so, Miyagawa was told).
Miyagawa, S., Berwick, R. C., and Okanoya, K. (2013). The emergence of hierarchical structure in human language. Front. Psychol. 4:71. doi: 10.3389/fpsyg.2013.00071
Miyagawa, S., Ojima, S., Berwick, R. C., and Okanoya, K. (2014). The integration hypothesis of human language evolution and the nature of contemporary languages. Front. Psychol. 5:564. doi: 10.3389/fpsyg.2014.00564
April 29, 2015