When McLuhan comes up with his general theory of communication and he tries to think about the relations among media, he starts with writing in antiquity, printing in the Renaissance and then the electronic media of the 20th century.
So this sociologist realized that in writing form there’s a crucial element that in the process of communication is particularly significant: alphabetic writing.
Then there were other forms of writing, like for example psychographic or ideographic, but alphabetic writing in the 9th century B.C., so about 3000 years ago, coincides with a jump in terms of civilization. One of the striking reasons is because alphabetic writing offers a simple form of representing speech. Furthermore, it presents a very economical form of representation.
So that is one major change in human forms of communication. An additional impact happened during the 15th and the 16th century, when typography was introduced. We witness an incredible process of mechanization of writing and so typography, the invention of printing press increased the effects of writing on human culture.
But subsequently, in the 20th century, we have completely difference system of communication, which is not based on mechanical media. Writing and printing are both mechanical practices for creating inscriptions. Human cultures developed a new kind of communication and media system which is based on electromagnetic radiation. New electronic media emerge, based on radio waves and other forms of electromagnetic radiation.
From that age, people have been faced with the innovative type of media: welcome to the new technological mediums and system of communication.