Children were taught to sing the landscape. When they understood the songlines, they could sing their way from landmark to landmark, over thousands of kilometers. The passage of time would erase this medium. But it was still a communication system of great power, because it might allow small groups to migrate with purpose and intelligence, to a known destination. Imagine that starvation is on the land, and that you, Homo erectus, know the songlines, but that Homo habilis, your older brother, does not know.
Media becomes a matter of evolutionary life and death.
My suspicion, therefore, is that media was born about two and half million years ago. Media is much, much older than the human race. The thing I like about this media origin theory is its missing link. We have no record of this theoretical prehuman medium. A marked trail is temporary by its nature, it could not survive the passing of its landscape.