Who built the pyramids?

I have a friend on Yahoo 360 named Luzdepaz. She just posted some information (in Spanish) about the pyramids, and I felt it was a good time to comment on that topic.

The pyramids in Egypt and in Mexico/Guatamala are similar in construction and were built in alignment with the stars. Scientists believe the pyramidal structures are older than any technology that could possibly have built them...but what the scientists lack is imagination! They believe that our current civilization is the smartest and most technologically developed that has ever lived upon this planet, but I think they are wrong. I believe civilizations come and go, perhaps due to catastrophic earth changes such as pole shifts and ice ages.

Some people believe that our ancestors built the pyramids with ramps and pulleys and such. Others believe that star people built the pyramids. I am not so sure where I stand in this debate; although it seems hard to believe that ancient peoples could have built such huge, geometrically accurate constructions, I think they could have done it. By saying that star people must have built them is saying that we humans aren't capable of such feats. Yeah, I know what we're taught in school and what "scientists" keep telling us; modern man is the greatest thing to ever grace the Earth with its presence.

I think the problem here is that we don't have accurate historical records to tell us just how intelligent our ancestors where (except for the pyramids themselves, of course, and maybe that should be proof enough). And perhaps our ancestors in Egypt and the Mayan world were in direct contact with the star people....
Perhaps the modern man is just too barbaric to be openly contacted.