At Stage I, our ancestors used a variety of signals, e.g. vocalizations, screams, hand or facial gestures, tongue clicks, whistling, etc. to refer to situations that were relevant to them, e.g. the possibility of danger or the discovery of food sources. This is the kind of communication that we can see in many animal species, with a varying degree of sophistication.
At Stage II, hominids start to use these communicative strategies in a more complex way. An utterance, a gesture, is no longer a simple reference to a given event, but also the expression of how we are presenting the information. Are we describing things? Are we narrating an action? Are we telling the others to do something? In a previous post I offered a complete explanation of these new contrasting elements and their relevance for human communication, using as an example what I would like to call the bee paradox.
At Stage III, some of the communicative elements described above, particularly those involving vocal utterances, undergo a further process of reinterpretation that we may call grammaticalization. They are no longer, or not only, used as a symbol of the real world (objects, actions) but rather as functional units that help construct the message, expressing abstract notions of the kind grammarians are familiar with: tense, aspect, number, case, etc. In fact, this process is the one that eventually gave birth to what we usually call a 'grammar'. It must be said that developments that took place at Stage III do not cancel those of Stage II: human communication is a complex phenomenon that involves both the 'grammars' of spoken language and the endless possibilities of gestures and exo-grammatical utterances (that's a nice word I've just invented...).
The transition from Stage I to Stage II is crucial, because it involves the emergence of symbolic thought, and it must necessarily be connected with other examples of complex reasoning, like our ability to make tools. Obviously, we are talking about things that happened millions of years ago, and that have eventually detached hominid species from any other animal species on earth. The fundamental change took place in the brain. The 'revolution' is in the way you encode the information. Maybe those ancient hominids did not have the anatomical ability to produce something resembling speech, but they did have the mental ability to use communication in this new way (Stage II). Let's remember: what we are dealing with here is communication, not 'language' or 'grammar'.
In both transitions, from I to II and from II to III, we are also concerned with a more specific problem: how a particular communicative element, i.e. vocal output, attained increasing prominence through time, eventually becoming the central element in our communication system. Let's go back to the beginning (Stage I). A group of hominids uses a repertoire of signals, including simple vocalizations in the form of syllables. Let's imagine one of these vocalizations, `wak`, with the following meaning: "danger, a bear". The utterance of 'wak' was probably accompanied by a series of gestures indicating the proximity of the danger or urging others to hide from it. But we can also imagine the the syllable itself was susceptible of being produced in a variety of ways, using intonation. This is something that is still an essential part of our communication system: there are dozens of meanings or shades of meanings that can be conveyed by modifying the way we produce a given utterance, without changing the words. We can say 'table', 'table!' or 'table?' depending on the occasion, and we can express doubt, surprise, fear alarm or happiness by just changing the intonation. We can also give information about the size of an object or animal. All these expressive tools were already available to those hominids, not only 'available' as an option but maybe inseparably attached to the vocalizations. Being born as a simple alarm call, the segment 'wak' was already provided with an intonation component that could be modified afterwards. Those utterances were not the neutral words that we find in dictionaries, or the boring sequences spoken by robots or the monotonous talk of some formal situations. They were full of colour. They were alive.