Yes, that! And on top of this complexity of life, it took like 4 billion years on earth (that's roughly 1/3 of the age of the universe) from RNA/DNA to intelli

Yes, that! And on top of this complexity of life, it took like 4 billion years on earth (that's roughly 1/3 of the age of the universe) from RNA/DNA to intelligent life forms that can talk about this on the internet. And during this time, no catastrophic global event has happened to undo all that development. Comparing Earth to other planets in our solar system (we cannot really compare to other systems, obviously), Earth is really lucky that there was no such catastrophic event. So many factors are important for this -- our sun is just the right size (not too harsh UV radiation (bad for molecules to be stable), not too small to make our orbit so small that rotation would stop (blowing away the atmosphere)). Our moon is unusally large for a planet like ours, yet it was vital for stabilising the Earth's axis (stable axis == stable weather) and slow down its rotation. And for the moon to emerge, a very nearly fatal impact from another body of the right mass (Mars sized) needed to happen at the right time (very early). At the right speed and the right angle. The availability of water and oxygen at the right times in Earth history where also quite a big unlikelyhood. And it goes on and on: Earth is unimaginably lucky. Taken all this together, I doubt that anyone could multiply the probability of life on a planet with the amount of planets in the Milky Way (or the universe) we think would be Earth candidates, and claim to have a sensible number. The later is an unimaginably large number, but the first is an unimaginably small number and also a very unknown number. So: we just don't know how often life happens. And also, detection is not trivial: it is not that easy to see other planets (they are far away), or alien space probes (they are small, space is large), other radio waves (they are weak), or any other signs of intelligent life.