[hosh]

It depends on the material. Incas uses knots for record keeping. Those are not as durable as burned clay. In our current global civilization with advanced computing tech, magnetic tapes, cdroms, and hard drives won't last very long. Maybe SSDs have greater durability, but they will also require computing tech to dicipher. I do not think the existence of surviving writing materials is a strong argument for evidence of civilization, and speaks more to the limitations of the technology.