I was thinking the other day, just like I usually do, but this time the idea hit me. It had hit me before, but always in dissimulated forms, so I wasn't able to grasp it as tight as I had now.
According to Maya, there are 'cycles'. A cycle happens every 10-15,000 years, taking the form of a calamity. During this time, a civilization has time to bloom. Not one civilization, not once, but many times, almost from scratch. The population grows, develops, then all of a sudden, something happens, and it falls. Antarctica had once the looks of the equatorial forests, and was located where the Sahara Dessert is now. Nowadays, it's hidden under layers of ice. Go and dig there for relics in the ground if you can! Find the cradle of civilization! Yeah, thought so...
We also know that once upon a time, the axis of the Earth was vertical, not oblique. There are two theories: first one says that something must have hit the Earth strong enough for the axis to change its inclination. The second one claims that the ice, having melted at some point, caused the Earth to shift its axis. Whatever it is, it was a calamity that changed the face of the nowadays earth.
I'm going to give you the Tsunami example. A small catastrophe compared to one that could wipe out a whole continent. But this disaster showed a point: it took no time to sink islands, places we'd hardly know about unless we were there to witness the phenomenon.
So there are Tsunamis. There are also floods, volcanoes, earthquakes - and these are only the dangers our planet makes us face. But in this galaxy and universe we are not living in a glass house: meteors, asteroids, comets, planets with weird trajectories float around us, minding their own business until something small happens, and the domino pieces start crumbling. It may take an instant, it might take thousands of years for them to hit us. Or they might never hit. Who knows? But the point is, we are here, on Earth, waiting for something to happen, and sooner or later it will.
If those poor people back then lived on an island and built temples and then a Tsunami came, then only the structures remained, underwater. And then, thousands of years later, experts come and say: "Impossible! Nature built temples, not humans!". I find it rude.
Have you ever heard those experts say: "Holy crap, man, can you believe it? The Olmecs, the Maya, built crazy things and then they just abandoned them!" Why would they build something huge and then leave? Of course, no one in his right mind would do that, but our experts are not aware of it. So, holy crap indeed! Well, maybe some of those people did have a reason to leave, but others might have never had any intent of leaving; they had the intent of living, but couldn't survive.
That's how it goes: you start building, and you develop. But then, you die. And something is left - survivors - and they migrate and populate other areas and they tell stories, which soon become legends, and then they become faerie tales.
Do you honestly believe that we will survive forever? On Earth? (If you think so, is your IQ around 100?) So maybe we move to the moon or to another galaxy, but how many of us will be able to do it? Put it like this: Titanic. A huge ship, struck (or as a hypothesis, in danger of being struck) by an iceberg. Boats are being let down, but there aren't enough of them. Some of the passengers maybe don't even know they will be hit by an iceberg: they are too drunk or fast asleep or whatever. Some people will embark on those boats and save themselves, but others will remain behind.
If we take it to a larger scale, what happens is: build ships for traveling to other galaxies before the earth dies. Will everyone move? Will there be place for everyone? Will everyone know about it? No. Some remain, and from the ones left behind, some will die. Then a calamity will happen and some people will make it and will adapt to the new conditions. Or maybe the calamity won't happen, but just miss us a few inches, enough for things on Earth to change again. It's just like my rambling: there's no formulae for it. Things can't go one hundred percept right - that's a fact.
In other words, civilizations bloom to fall. That's the story of life. You deny that, you have no respect for anything else but humankind, which is nothing, but a jar of insects thrown into space.