I think it was Nat Geo that I saw a show about archaeologist and the new theories they are developing when it comes to said mystery, much of it leaning towards a time of famine & drought and quite possibly algae bloom along the coast. The Mayan & Incan groups relied heavily on trade goods, so when the source for food stuffs dried up down stream or along the ocean coast for long periods of time, starvation happens along with pestilence, etc. Toss in human sacrifice and war over food stuff and voila! We have the most likely answer when it comes to the core behind their "vanishing". Toss in a handful of born-again Spanards who murder in the name of God, Gold, Slaves & Silver not to mention the disease they are bringing with them and voila! The final piece to the puzzle brings things together. . . or so the theory seems to suggest. There is one other very important part to the mystery which ties to another issue as well (Neanderthal) . . . the fact that the Spanish have a very unique tactic of taking over territory -- the literally propagate. . . be it by rape or one night stand, they make babies and in turn, absorb cultures into their own fold. . . just look at the U.S. and what's happened in the past 50 or so years