Objects Do Not Forget
A bored accountant in Uruk presses a reed into clay and becomes the point at which knowledge stops being as mortal as the people carrying it. Something is gained, and something quieter is lost.
Somewhere in Uruk, about five thousand years ago, a man is pressing a reed into wet clay to record a quantity of barley.
He is a bureaucrat. He is almost certainly bored. He is not writing literature, or philosophy, or poetry; those are centuries away, and they will need a script far more capable than the one he is using. What he is doing is stranger and more consequential than any of them.
He is putting something outside his own head.
For roughly three hundred thousand years of our species, everything anyone knew existed in exactly one place: a living human mind. This man is the point at which that stops being true.
It is worth being precise about what changes, because "the invention of writing" is one of those phrases that slides past without landing.
Before this, knowledge was exactly as mortal as the people carrying it. When a master astronomer died, her observations died with her, unless she had trained an apprentice carefully enough and for long enough to carry them forward intact. When a community was scattered by war or famine or flood, its accumulated understanding scattered with it, surviving only in whatever fragments individual survivors happened to remember and happened to pass on.