Are there any surviving written documents from ancient Greece or Rome? I heard that writings we know today are copies done by either medival Christian monks or Arabs. If that is true, can they be trusted to do exact copies without their own significant input or censuring? And did originals texts survived until medival periods, or was there a need to copy them every few years?

How did some native American cultures (Mayas, Aztecs, Inkas,...) despite thousands years of completely separation from "old world" independently developed many similar fetatures, institutions, societial structures, habbits, etc. like in old world, for example agriculture, living in cities, organized religion, empires and kingdoms, waging wars, having "nobility", marriage, slavery, having markets for goods, building bridges, irrigation, boats and ships, stone houses, even pyramides? Or maybe better question, where these features really that similar or is it our simplified view?