This paper asserts that the first instances of linguistic communication between early humans were characterised by the use of consciously invented signs. This position is in contrast with what is presumably the mainstream view on the subject, which holds that language is the result of a biologically acquired communicative skill that spontaneously, instinctively, started to manifest itself in the mouths or hands of the very first language users. By pointing out the inextricable link between linguistic production and conscious thought, it is asserted that the first true linguistic items that emerged on the evolutionary scene could never have been produced had a higher level of consciousness not come to characterise the human mind, allowing it to perform ‘thinking about thinking’.