alsih2o said:
everything else is stories form history. these vary wildly in accuracy.
Defining history is tricky. Linguistically, the word comes from "His Story", which implies a narriative of sorts (do you remember the feminist groups starting up "Her Story" classes in protest of the male-dominant term?). This makes sense, because that is how history was passed down and learned for the longest time, as stories told from one generation to the next. Even after the stories became written, they were still really just stories.
Even now, in History class, you learn primarily the stories of the past. They might not be as colorful as the stories they told 500 years ago, and you
assume that they're based on verifiable fact, but you can never be sure without doing the research yourself, and only a few people bother.
There was/is a movement to leave out the Holocaust from public school history books because it's not appropriate for children to learn about. Considering how many people stop learning history after high school, how long would it take for
widespread public knowledge of this incredibly important event to just... slowly... die out? One generation? Two? Five? So far the movement has made no headway because history teachers everywhere know better. Their mantra is "Those who forget the mistakes of the past are doomed to repeat them." With that in mind, there's no way they're going to stop teaching students about the Holocaust.
Which brings me back (roughly) to the topic of this thread: how much history has been lost? One of the primary tactics of civilizations trying to assimilate/conquer other civilizations is to control what is taught to the children. The US did this with Native American children - forced them into public schools, forbade them from using their native tongues, etc... More heavy handed countries, like China in Tibet, go much farther, and simply kill the elders who know and pass on the history and culture of their people. In ancient times, invaders would often kill the entire population, excepting only the youngest children. It is a ruthlessly effective tactic, and the histories of such destroyed civilizations are virtually eliminated, excepting the biased records of their conquerers and archiological evidence (which is also often destroyed. A lot of the pre-Christian shrines and temples of Europe were destroyed and churches built in their place. What they could have taught us is lost forever.).
Ultimately, we logically
cannot know how much of history remains unknown. We would need some way of quantifying the amount of knowledge that is not only lost, but that we are
unaware of being lost, there no longer being any evidence of it ever having existed in the first place. This is, sadly, impossible.