[Finnster]

OK, so my take is this:

In order for ET life to have assisted all the pyramid builders all over the world (there were many on several continents over centuries) a number of extraordinary things would have had to happen:
-ET life exists in our galaxy
-It exists close enough they can find us
-They have means to travel fast, really faster than light unless they are super close, which our current understanding of physics does not allow
-->the closer they are, the more likely we should have detected them by now (radio waves, etc)
-have ability to communicate w/ us, even tho we may be completely alien
-They wanted to help us do silly things, (ie stack rocks)
-They left w/o a trace, and have never come back

OTOH, perhaps people were far more clever than we are giving them credit for. Between the two choices, the latter seems far more plausible.
You know what flips my lid? The fact that we could use 60's technology to lift someone off the planet in a titanium chevy Nova strapped atop a million pound roman candle designed w/ pencils and slide rules, fly safely across the dead vacuum of space, land all the way on a moving object exactly where they wanted, land on the moon w/o crashing, joy ride around in a fraking golf cart, and turn around and come all the way home riding a flaming fireball thru the atmosphere and safely crash in the ocean. And no one sunk to the bottom nor died some horrible death they rightly tempted 10,000 times a day.
That is some crazy ass shit, and we did it. Several times.