The spacing of the planets isn't due to random chance. They are all in orbits defined by resonances with the other planets, as they effect gravitational drag on

The spacing of the planets isn't due to random chance. They are all in orbits defined by resonances with the other planets, as they effect gravitational drag on each other. They have pushed and pulled on each other for billions of years, until they have settled into the ordered structure we see today. https://en.wikipedia.org/wiki/Orbital_resonance https://en.wikipedia.org/wiki/Orbital_resonance It could also be well possible that this sort of stability is required for multi-billion year evolutionary processes to take place. Systems with more chaos would likely also have chaotic seasons even if their planets were to have the other needed conditions for live. If the summer-winter cycle were more unpredictable that it is on earth, maybe that acts as a limit on the complexity that live can achieve as it would constantly be getting pruned back. Systems with "unstable" or "irregular" planetary arrangements are probably just in an earlier stage of development, and might likely lose planets or push them into more stable orbits eventually. Similarly "stable" or "ordered" systems are likely just older systems which have been able to develop without being disrupted by outside phenomena. In that sense looking for well structured systems might be a good place to start looking for life, as they are likely old and stable enough to have had evolution take place.