My Theory
The mayains are a tribe of regular people just because they made a calandar out of a rock does that mean it really does something in other words yes i believe they probably just ran outta room like on a regular calendar and they did'nt get a chance to make another one because they got killed off by the spanish or some people with guns also they were not that smart if they were smart would they have made something or what not so i conclude that they where just average tribal people like indians and where smoking some plant or eating infected animals...
(i don't need to say which plant...)