Just because it's the old standard Sagan Rap doesn't necessarily mean it has to be wrong. Like I said, it's only circumstantial evidence, but it is compelling. As for the alleged nixing of exobiology by the biologists, perhaps they simply cannot accept that there are alternative metabolic pathways possible, or that if not, evolution is perfectly capable of independently rediscovering the same ones elsewhere. After all, we're not talking exotic biochemistries here, just carbon-water based organisms.

It's unfair to slam the space groupies for that, just as it's unfair for the astronomy crowd to point out that the primary contributions of biology since the discovery of DNA was finally getting the number of human chromosomes right, and substitution of the term "quadruped" by "tetrapod".

As far as the statistical impossibility argument, I find it impossible to accept that on the ONLY world where life arose, intelligence ALSO arose, and that that intelligence ALSO developed the technical capability to do SETI. That is starting to sound a bit too much like Intelligent Design, even if you prefer to call it Anthropic.