Why do historians believe that this civilization will be destroyed?

Historians believe that our civilivation will be destroyed because of proof from past civilizations. The Mayans, Incans, and so many other cultures were destroyed from disease and war. As we get smarter, though, we get deadlier. The Mayans were extremely smart...they invented planetariums and the calender. Therefore, as we invent giant nuclear weapons and scientists begin to break the confines of the box we have been living in, the world is contisuosly falling into a spiral of no return. One monster diesease and we could easily be wiped out, leaving the world to deranged scientists with a different view of what society should be. By different view, I mean brainwashed. But we cannot blame ourselves, because it is human nature. The whole 'eye for an eye' thing is getting old, but yet it continues. We can break history, it isn't impossible, but the facts line up...we can fail like past civilizations.