Nick Hoffman recently pointed out that any planet which does not have a Moon (or some other gravitational perturbor), does not have tectonics. Thus it separates into layers of solid and water, and thus intelligent life is unlikely to evolve on it.

It was then suggested that a planet in orbit around a gas giant would layer with 2 dry areas surrounded by water -

The fact that if a planet does not have tectonics and a molten core it will have no shield against radiation was generally ignored in the discussion -
this radiation would also prevent the evolution of advanced life forms and thus of intelligent life -

My thinking now is that tectonics are required for the evolution of intelligent life, and thus that the existence of either a moon, or a large planet in a nearby orbit around the star are prerequisites for the evolution of intelligent life - perhaps the requirement can be satisfied in dual systems with a star and brown dwarf as well -

EP