First of all we have to imagine what the "shape" of history is. Is it the population explosion? The proliferation of cities? (Rural to urban shift.) The scientific revolution? (Alchemy to Nuclear physics.) How about a communication explosion? In that case the standardized alphabet and dictionary would be the most important "invention". Actually nevermind; the single most important invention has to be the ocean going ship. Leif Ericson reached North America 1000 years ago and then 500 years later Columbus, backed by a larger, Imperial and "globalization-ist" population busted into this hemisphere and wrecked the whole place. If you minus proper sea worthy vessels out of the last millennium then who knows what civilizations would have independently risen on either side of the Atlantic. Until the Wright brothers came along maybe no one would have crossed it at all? This is of course silly. Engineers building bridges but not boats. (?) The slave trade would never happened too.