How did writing systems come about?
Today we take it for granted that we can communicate with each other by means of the written word and yet reading and writing are not naturally learned skills. They have to be taught specifically.
How did humans first realise we could make marks that others would recognise as representations of things in our world?
How did those marks evolve into the complicated sets of symbols we use for writing today?
We might go some way towards answering this question by drawing a parallel between the development of children – and how they learn the significance of signs and symbols – and the development of early human beings in general.