History needs some tightening

I recently finished reading a book entitled "1421" by Gavin Menzies on a recommendation from my father. This unassuming name belies the awesome found within. Apparently, the Chinese discovered and colonized North and South America and Australia whilst circumnavigating the globe and figuring out how to judge their longitude, something the European's didn't figure out till the eighteenth century, by the 1430's. Why have we not heard of this sooner you ask? In the fifteenth and sixteenth centuries China became very xenophobic after successive decades of internal strife and the emperors decreed that all documents pertaining to the voyage be destroyed and the colonies left for dead. According to some DNA evidence, the colonists appear to have melted into some of the local populations. Pretty cool.
History, tighten your shit up. How many other cool things have you let slip through your fingers like Governor Tarkin's star systems (Star Wars reference...get over it)? I want a 100 word essay on how untaught you have been on my desk on Monday.