Many language theorists assume that there is a clear boundary between linguisticity and non-linguisticity. They believe, then, that spoken language is what distinguishes human from non-human. Unfortunately, this categorial distinction is challenged by Darwinian evolution, advances in evolutionary biology are more finely grained than a single definitive jump to linguisticity.
On second viewing, however, their assumption may find backing in the language of criticality. The notion of criticality, as understood in statistical mechanics, covers a range of behavior in Nature that has one thing in common - the onset of a sudden change in observable features that constitute a system. The concept of system is one that is adequately supported by the framework of statistical ensemble - the descriptors of groups of elements that share common features. Examples of criticality involve the cyclical explosion in gypsy moth populations, structural changes in water as it turns to ice, catastrophic environmental changes such as earthquakes, volcanic explosions, tsunamis and so on. Here examples of systems are the populations of gypsy moths and water molecules.
Physics, biology and economics are fields that have used the concept of criticality to explain and formalize many phenomena. Criticality is often associated with structural changes in systems. These changes can be striking enough to confuse us in our beliefs about the nature of a particular system. For example: without experiencing the melting of ice it may be difficult to realize that both solid and liquid are related states of H2O. The molecular constituents of H2O are unaffected whether it be in a liquid state - water - or in a solid state - ice. The states are dramatically different. In the case of H2O, the state transformation from one to the other is brought about suddenly at a critical point at which the presence of heat, or lack thereof, will either melt the ice or freeze the water. We believe that in the study of more complex phenomena, similar behavior occurs can go unnoticed because the structural changes are so dramatic that related states of a system are considered separate systems. Language falls into this category.
Chomsky [13], for example, was one of the first people to advocate a Big Bang theory of language with the suggestion that change occurred at the ``genetic'' level. He was implying that fundamental structures - genes - had been affected with the emergent features - linguistic capacities - being the consequence.
We would like to paraphrase that view in terms of elemental physical processes. For our purposes, these processes can be described as mechanical, chemical and nuclear, each operating at increasingly fundamental levels.
The simplest processes, mechanical, are the most abundant and least fundamental. For Chomsky, the changes that gave rise to the new linguistic abilities occurred at a more fundamental level altering the underlying structure, not just rearranging the constituents. His use of ``genetic'' is comparable to the description of chemical.
For ourselves, we advocate a physical change akin to a mechanical one and not a chemical one.
This being said, we are more inclined to side with Calvin and Bickerton on the idea that language is incidental to other modes of interaction, and with Bickerton and Corbalis on the idea that criticality in structural changes plays a role in the emergence of language (but without necessarily involving mutations at the genetic level or fundamental structural changes with the size and general morphology of the brain).
Derek Bickerton [10] thinks that humans stumbled incidentally onto language. He also holds that language is not a cultural event that derived from the need to communicate. Rather off-line thinking - the capacity to imagine - possibly brought about from proto-language, opened the possibility for the emergence of language. Bickerton's theory stresses the impact of evolution on humans and how language has been used to preserve homeostasis, that is, the preservation of conditions that sustain the the viability of an organism. Simply put, language is a by-product of survival and more specifically, an incidental effect of the capacity to access situations pre-emptively.
As we have said, some of Bickerton's ideas imply notions of criticality in structural changes in the emergence of language from proto-language. Bickerton defines proto-language as a primitive form of language that would be as much part of early human biological endowment as present human language is, though without any of the grammatical or formal features that are usually associated with language. He argues that proto-language is more robust than language because it has been part of hominid biological endowment for much longer than language. Moreover, proto-language does not have a critical period of acquisition though it depends on the presence of lexical input. Bickerton thinks that the faculty of acquisition for proto-language and language are disjoint and the acquisition of proto-language does not necessarily lead to the acquisition of a grammaticalized form of language.
Bickerton based this supposition on several studies of pidgin languages (such as pidgin Hawaiian, pidgin English, etc.), linguistic features in early childhood, ape language, and human adults deprived of a linguistic environment. He calls forth these examples to describe the criteria that define a proto-language. According to his theory, proto-languages lack the formalisms of natural language such as a grammatical structure, the use of tenses, and non-lexical vocabulary.
From such examples as pidgin languages, he also attempts to demonstrate how proto-language can lead to language without intermediate steps. Infants make the transition from infant forms of language to adult language in a few months while the transition from pidgin Hawaiian to Hawaiian creole was achieved only after one generation (Bickerton considers creole languages as meeting all the criteria of natural languages) . Bickerton suggests that hominids may have gone through a similar critical period from proto-language to language, though a sudden transition. It may have taken a few thousand years, a short time in hominid/human history [9].
Interestingly enough, in The Language Instinct Steven Pinker [46] uses similar linguistic samples to make an argument for the genetic innateness of a linguistic faculty and a shared universal grammar amongst humans. Unlike Chomsky, he is an advocate of evolutionary selection, but believes that the precursor of language is somewhat mysterious. He suggests that linguisticity has probably evolved from genetics (such as primate calls) rather than learned behavior1.3.
Despite present physical evidence, it is very difficult to establish the origins of language. This is due in part to the difficulty of establishing the scale of evidence, the granularity at which language should be considered. There is a perceived boundary between a language and pre-language state and it is unclear how to capture its quality. Is the boundary gradual or sharp? Is it along the history of humans and hominids or is there a sharp delineation between other primates and humans? These are a few of the questions that still require answers.