We have moved from an evolutionary sound and gesture to the oral word, which has absorbed and the sound and gesture and the spoken word to the written word. However it is unlikely that this process was linear, most likely parallel - to-serial, for PRandrank just has it all. This means that any phenomenon, including such as sound, gesture, word, writing, etc. is due to the entire process of development of humanity and its environment. Respectively, and each such phenomenon from the infinite variety of phenomena it contains, in compressed form, the history of man and his environment.
We do not refuse from the concept of sequence is widely adopted in classical philosophy and, consequently, of sociology, for each phenomenon develops according to the principle of the unity of place, time and action, one of the tenets of which reads as follows: in one place at one time, may be only one action. Spatial and temporal parameters exclude the possibility of simultaneous action, but they also exclude the absoluteness of any of these parameters. Definition of primacy indicates the presence of dominants that leads subordinates other phenomena. So sound, gesture, word, writing at a certain stage in the development of history became dominant, which led to the solution of some common problem.
So when we talk about the letter, and then about the text, how about some independent phenomenon and stage of development of human history in the process of socialization, which is based on specialization, we mean that the letter at some point becomes dominant, which minimized contains the whole history of human development. And this equally applies to any message that contains some common information and information that goes far beyond the visible and conscious content.
The word is a unique entity, which contains sounds that reflect a certain set of objects of that world which is outside of human consciousness. However, this set has at least two natural beginning: the first is always the sounds and visible objects; the second reflects the sounds, and objects, which themselves are not directly visible expressions, such as feelings, thoughts, assumption, desire of the type: "I will eat you".
The latter (i.e. the sounds that Express feelings, thoughts, etc.), is of particular importance. By itself, the gesture does not require audible symbols and visible objects. Need in sounds was due to many reasons: the transfer of information to another that is outside the field of vision, the need to transmit information about non-existent at the moment, a situation, etc. But the most important, probably, were formed the need to identify such specific objects that are not visible, not detected, for example, the feeling of gratitude, love, as well, and possible dangers, etc.