The Hopi Indians like many native tribes that have lived in North or the south Americas have taught their people what there ansestors have taught them and it is passed from generation to generation.

These teachings include such things as where did they come from and what to look forward to in the future This is one of the myths that has been passed down :

The Hopi descended to Earth from Alien life. The Earthlings were set up in underground caves ( 3 caves ) and left to procreate. The Alien project was so successful that the Cave people overpopulated the underground world and were forced to learn to survive in the harsher climates on the surface. This of course would have take milleniums to play out.

Throughout the ages prophecies and warnings were shared by Hopi visionaries and shaman.

One such prophecy goes like this.

"When the Blue Star Katchina (spirit guide) makes it's appearance in the heavens, the Fifth World will emerge. This will be a day of Purification."

Another prophecy:

"When the Saquasohuh ( Blue Star ) Katchina removes his mask there will be no more ceremonies for a time. Only the homelands will be preserved as an oasis for the Hopi."

This could be translated in several ways to something like:

Mother Nature will force humanity back into a cave, or warring bodies will destroy the surface world and the only refuge will be in a cave.

In whatever manner the prophecy unfolds it would bring about the emergence of a Fifth World. The Fifth World evolves and seeks out the Sixth World and the Seventh and so on and so forth goes the legend.

http://www.crystalinks.com/hopi2.html good thuoughal link