Martin 53N 1W wrote:

Paul Bramscher wrote:
[...]

So if there was some chemical marker in the cosmos which allow us to find advanced organisms directly (not indirectly, via technological or chemical markers of behavior) we might open up a whole new aspect to SETI.  Would be nice to have a hypothetical "DNA telescope."

Or just look for spectrographic smog (artificial pollution).

Again, though, that's a chemical marker of behavior (which has been suggested too, and I hope it holds some promise).

But I'm wondering about directly detecting DNA or some other molecule of sufficient complexity to play host to an intelligent organism, brain waves, etc.  Some direct evidence, without behavior dependencies.

Impossible currently, but who knows what the future may hold...  The problem is that without engineering or large-scale environmental change (environment including atmosphere, noise on the electromagnetic spectrum, etc.) intelligence by itself doesn't seem detectable over any great distance at all.

So it may be that larger clusters of intelligence (large cities) will be one of the earlier potentially remote-sensible artifacts of intelligence.  For example, cities might be approached as (often, in today's modern sense) having some signature (chemical, albedo, geometric, etc.) which make them often stand out.

We may never be able to pick out an alien's brain waves, but we just might detect a city on an earthlike planet in the next century or two...