Renewable Revolution

http://www.youtube.com/watch?v=JqYO4rA12EE&feature=player_embedded
The above computer animation of a pole shift causing catastrophic rapid crustal movement could easily explain why the frozen wooly mammoths in Siberia were found with flowers and plants in their stomachs that simply do not grow in a cold climate. The flash frozen bodies effect would certainly take place if Siberia moved a thousand miles or more towards the north pole in a few hours. 

Something like the above, even if it was a more gentle shift of, say a thousand miles or so, would be enough to cause massive tidal waves and the destruction of most land based, ancient civilizations.

The few survivors that happened to be far from populated areas very high in some mountains, without education or knowledge of the past, would not, as occurred when the Spaniards asked the Incas about the ruins at Lake Titicaca, know who built them or how to duplicate the precision in stonework and joining. 

And all that was centuries before more pre-Inca ruins were discovered.

Aug 23, 2000 - The ruins of a pre-Incans ancient temple have been found under Lake ... of the lake, sited in the Andes mountains between Bolivia and Peru. 

http://news.bbc.co.uk/2/hi/americas/892616.stm