Somewhere in some remote corner ofEquestria, a group of pony archaeologist discover the ruins of an ancient human civilization, complete with human remains, ruins of buildings and tools, and scrolls written in a strange language. What would they deduce from us?

Depends, are the ruins modern buildings or ancient. Are they seeing humans from a thousand years ago or modern day.

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I was thinking that it would be similar to a bronze age civilization.

3352882 Don't forget that the reason the Greeks and Romans didn't advance much technologically was their anti-tech bias (their god of technology was a cripple who couldn't keep his wife interested).
A bronze-age culture doesn't have to be as primitive as the Greeks and Romans. The Romans had everything they needed to make automatic weapons, and the Greeks invented a steam engine. The printing press doesn't require iron age tech, and there are very elaborate stone age astronomical observatories.

I actually have this idea for one of my episode ideas stories called 'Of Men and Ponies'.