[bsder]

> Did we lose a substantial amount of previously developed knowledge when the Greek or Roman civilizations collapsed?

We lost an enormous amount of knowledge in those time frames.

It took six hundred years for the Romans to reach the same technical level as the Athenians. It then took almost one thousand years for the Italians to again reach the same level as the Romans (this time being greatly increased by the shenanigans of Catholic church).

That was the whole point of the rediscovery of "classical" knowledge from the "ancients" in the Renaissance.

[Mediterraneo10]

> It took six hundred years for the Romans to reach the same technical level as the Athenians.

When we speak of Ancient Greek technical innovations, we're usually talking about the Hellenism era. That was after Athens had begun to wane as a major intellectual center, and much closer in time to the Romans' ascent in the Mediterranean.

[PaulDavisThe1st]

I think we need to differentiate between several different things:

  * the social organization and structures required for technologically complex societies
  * the knowledge required for certain technologies
  * the loss (or otherwise) of knowledge by humanity, as opposed to local loss of knowledge