I dont know, but, most logical starting point is the source, ancient astronomy.
If looking those "doomsday" prophecies from that point of view, the prime reason
to cataclysm should be some alignments/conjunctions in the space.
And from there we could specalute many things.
-Solar Storms
-Pole Shift of Magnetic Field of Earth
-Cosmic Radiation from Milky Way, some speculate that it is the light that alters DNA,
from there speculation of Leap of Evolution.
-4th Dimension comes to reality, SpaceTime ceases to exist. Every half of the wheels turn is SpaceTime, the other TimeSpace.
-Time Travelling
-PlanetX the NIBIRU, 10th "planet", Brown Dwarf Star visiting near Earth every 6000 years or so causing great havoc in Earth, every kind natural disaster you can imagine plus its gravity will force Earth to stop spinning 3 days. Its rotating our Sun in big ellipse, opposite way to others planets in our Solar system.
There is so much going on about that, dont know even half about what all those theorys
include. If you really want tripin in 2012 opening of...... well, everything, try this...
"Mystic Syncronism"
This dude is deep in it, so deep that I dare to follow, but, hes pointing out very interesting connections going on in inner/outer world of ours.
Remember, I warned you
The vids are very addictive...
http://www.youtube.com/watch?v=wbewGohciYw&feature=related
http://www.youtube.com/watch?v=dfDIVJXkfCU&feature=related
No matter if hes wrong or right the amount of knowledge about different areas is big.
Many pieces of art and lyrics has opened to me as before they went over my head.