Other civilisations in the Galaxy - are they really that likely?

I have always been fairly conservative (dismissive even) regarding the possibility of other "intelligent" life in the universe. This comes from gut feeling, aesthetics(!) and the Fermi paradox. Now it's time to get scientific with the issue, as there seems to be a good number of experts around here in the relevant fields. I'm looking at a sort of "informed" Drake Equation...By stipulating Galaxy, I'm just giving us a working number of star systems. I'm quite happy for this to branch out to the observable universe once we have a handle on the numbers.My opening comments...What's the earliest opportunity for a suitable planet to form?What conditions do we really need for abiogenesis?How long do we need to wait for abiogenesis? (~1Gyr in our case)How long for progress beyond prokaryote stage? (~2Gyr in our case)Now, where to put it? Origin of Life?

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