The Sixth Sun

Over 25,000 years ago a humanoid race stumbled upon the earth. They were amazed that the humanoids on the earth were quite similar to them as their colonization efforts had never led them to an inhabited planet. Deciding to watch and wait they witnessed five natural disasters destroy most of the life on Earth, but each time mankind proved resilient.

Finally, the leaders of the home planet, Osiriat, decided that mankind could become an ally in space and decided to help him once he reached that point. They also noticed star signs/alignment patterns that would clue man into upcoming disasters if he would learn to read them. The fifth mission to Earth secretly built the pyramids of Egypt and Meso-America, but instead of reading the signs, man interpreted them as signs from the gods. Knowing mankind was doomed to disaster in the earth calendar year 2012, the leaders of the fifth mission decided to send their children on the sixth and final mission to earth to rebuild society, this time as a mixed race.
Why didn't mankind locate Osiriat with his long range space based telescopes? Because it is hidden in the binary Sirian system. The two suns of this system are too bright and hide it well. Besides, man was looking into deeper space for habitable planets.
Why didn't man read the signs? He did, but his perception created gods and then God. Once he had the "answer", the structures which carried the signs became tourist attractions.
Why do I discuss the next 4300 years? To answer the questions, "Will history repeat itself? and Will mankind learn from the past and save himself?"
You decide.