Erik Max Francis wrote:

"Steven D. Litvintchouk" wrote:

The entire SETI endeavor depends heavily on two assumptions:  One,
that
we can guess how the advanced alien civilizations communicate; and/or
Two, that advanced intelligent civilizations want to communicate with
more primitive civilizations like ours and so will choose a mode of
communication that we already know about.

Actually, it only requires the latter assumption.  SETI is not looking
for incidental communication, it's looking for deliberate, simple
broadcasts made by aliens to us.

But advanced aliens trying to make a "simple" broadcast to less advanced civilizations (like ours) can't even assume that the less advanced civilizations have active SETI programs searching for *them*--or just what such SETI programs might be doing to search for them.  Logically, therefore, they may send a message via a mode of communication that is so simple and obvious that we will eventually spot it even without an active SETI program.

That was the theme of "2001: A Space Odyssey" (and the short story "The Sentinel" on which it was based):  We didn't need SETI.  Those aliens left behind an artifact that was easy for us to accidentally stumble across (as soon as we had developed technology sufficient to begin serious exploration of the Moon).

As in "2001", I wouldn't be surprised that when we finally find evidence of intelligent extraterrestrial civilizations, it won't be found by any of the dedicated SETI searches.  Because advanced aliens can't assume that such SETI searches are being carried out by us anyway.