Was bored yesterday and watched a documentary on this... A young scientist traveled the world looking for clues on this.. I'm kind of on the fence about this whole deal, but it was interesting to watch to say the least...
The Mayan calendar began approx. 5000 years ago... So they looked into a possible event close to that time... This guy found proof of a deadly polar shift that occured 5,000 years ago.. he found proof in 2 continents.. Ice caps melting and retreating have uncovered plant life that has been frozen in time so to speak for the last 5,000 years... The "ice man" who was found in 1991, was dated back around 5,000 years...
Problem is, how do we know for sure that they weren't planning on continuing the calendar? how do we know that they weren't forced to abandon their city before they could finish their calendar?
Also, there is no way they would be able to predict the increase in population, the advancement in technology, etc etc...
I'm sure the world isn't going to end on 12/21/2012, but it's definetely an interesting topic...