I assume this is what would happen if Equestria was built on or in a world containing the ruins of “modern” human civilization. In between magic and its random abilities and effects, nature being a controlled process in most if not all places, and the various other factors in the world, human remains and technology could have survived way longer and in far better condition than they would in reality.
 
Hell, maybe a lucky few humans survived somehow as well (controlled stasis comes to mind, cryogenic or otherwise).