if there really were an advanced alien civilisation out there in the galaxy, we probably wouldn't know they were there...
think about this:
1000 years ago, we sent messages via physical means, for instance, couriers, ships, horses, smoke signals, lights, carrier pigeon and then about 200 years ago we had discovered the telegraph
and today we have planes, radio, telephones, satellites and the internet....
Point being is that we keep finding better and faster ways of communication, ideas that we totally would not have thought possible centuries before they were finally invented, so any advanced civilisation that is capable of building space ships is also likely to have an even more advanced form of communications than the basic radio signals that we send for long distance communications.
At our current level of technology, it's likely we would not even be able to detect any advanced form of space-alien communications and even if we did, it's likely that we are dismissing it as some sort of background "noise" from space because the signal is too faint to detect so it gets lost in the cacophony of signals coming from space.
an example of an advanced form of communications an advanced alien civilisation might be something like "sub space" communications like in Star Trek, where near instant communication is available over light years. If there were such a thing as sub-space communications right at this moment, we would have no idea that it was being used.
Imagine if one day we discovered sub-space communications and all of a sudden we are bombarded with 50 million simultaneous incoming message channels from thousands of alien worlds from all over the galaxy
So maybe these advanced aliens that have been around for a million years or so have been stopping by every now and then, maybe they stopped off once or twice a couple of millennium ago, and gave us a thing called "religion" by pretending to be gods, and maybe they actually had the best of intentions, and religion was given as a test, a test that we failed miserably.
Maybe these advanced aliens have been through galactic wars between different species before, and "The Galactic Council" has declared that all sentient species with the likelihood of developing space travel be given a test of their ability to "get along" with everyone?
Insert multiple religions all over the planet, to either teach us good moral behaviour, or have us turn on each other until we learn how to "get along" with each other.
Seriously, if not for the dark ages we may very well have become a space-faring planet by now where travel all over the solar system is a common place event. imagine if the (non-christian) Roman Empire didn't fall?
Instead of us having the dark ages, the bloody Romans discover space travel by about the 1200s, colonise the solar system, move Venus into a 'cooler' orbit and turn it into a greenhouse planet to grow food for the solar system, and then we get our butts out to the galaxy at large by about 2000 and start finding other species to conquer or at least other habitable planets to ruin, imagine the Roman Empire, Mongolian, or some Islamic caliphate expanding for light years? *sigh*
so aliens, stopping by every so often, saw how disagreeable we were with our own species, as well as wiping out other species here on earth, and thought that it was a good idea to send us religion to teach us to behave, or slow us down.
maybe we've been so bad that it's Galactic Law that we must grow up slowly? and maybe there's even a "no fly zone" of four light-years around our sun? So maybe it's best that we get this angry streak out of our systems before we get out into outer-space and piss all over it as well?
mostly written 2011-Feb-05 ... mostly ...