Extremophiles don't tend towards complexity, though. And if each common variable has, say, a 10% range in which complex life can occur, you don't need that man

Extremophiles don't tend towards complexity, though. And if each common variable has, say, a 10% range in which complex life can occur, you don't need that many to start reducing probability a lot. - Orbital stability? - Tidal and seasonal ranges? - Magnetic fields? - And the big one - properties of our Sun & solar system that make it different to others of a similar age? For example, are there galactic-scale properties that affect the surface environment of planets on a long enough time-scale, so that, just as Earth exists in the habitable zone of our Solar System, there is a relatively narrow galactic habitable zone? All the more reason though to get some telescopes built that can glean more detailed information on exoplanets. We might be in for another shock like the Mariner probes, or it might be 180 degrees the opposite.