Men must have been definitely communicating amongst themselves before invention of script. Even after invention of script, which must have been the preserve of the privileged few, record of events, epics, traditions, stories of valour, songs, etc. must have been passed on from generation to generation through oral tradition.
In India even after the advent of script, Vedas were to be learnt only from a Guru though oral rendition and never through reading. One reason could be the need for chaste pronounciation and correct intonation (swara). Another reason could be the selfish desire to keep it the preserve of a few.
On another plane, till the advent of gadgets like phonogram, record-player, tape recorder, etc. music was preserved entirely in the minds of a few and passed on to the disciples through word of mouth. Not only the lyrics, but the entire style (Bani or Gharana) was preserved and carried forward by the Gurus and Sishyas through oral tradition. This is true especially in Indian context because, notation is just not possible as in the case of western classical music, as Indian music, whether Carnatic or Hindustani, is based on Manodharma or innovation on the spot and not put in a straightjacket.
It is mind boggling to realise that there were and are well-versed veda pandits who could chant thousands and thousands of lines from memory even while learning new lessons and practicing what was learnt already.
Likewise, the reportaire of an eminent singer, who can elaborate a raga, brings everything from out of his memory improvising the style and duration for that particular occasion, particular mood, particular audience, is also something to marvel.
Likewise historical events, mythological stories, etc. are sung by illiterates all learnt by rote. There were songs for every occasion and every chore to lessen the burden of the task or for mere merriment. All these are passed on through oral tradition.
The tradition of making children commit to memory is a continuation of this process.
If we are to preserve the vast trease trove of our culture, epics, sagas, language, history, we should nurture our tradition of imparting knowledge by rote. Mere publication or recording alone will simply not be adequate.
One food for thought! How many mothers can sing a lullaby today?