For what it's worth, the classic Drake Equation is that old "back of the envelope" calculation they put together to try to ask this very question - what's the l

For what it's worth, the classic Drake Equation is that old "back of the envelope" calculation they put together to try to ask this very question - what's the likelihood life evolved? The problem with the drake equation is it had several variables for which we had no flippin idea what the values were. For example, supposing there are a bajillion stars (we know that much), then we have to multiply against how likely it is for those stars to have a planet - and at the time, the likelihood of planets was completely unknown. That at least, is something that's changed in the last decade, thanks to new telescopes. We've addressed one of the Drake Equation's big unknowns: we now can hazard a guess that planets are extremely likely. Sadly there are enough other unknowns that we still can't make any sort of conclusions, but at least the betting odds are going up.