These are speculative and rather weak. Like most theory in this area, it takes the form "Look at these features of the development of life as we know at; if they weren't there, it couldn't exist!". But of course, they are simply unable to imagine, much less predict, what happens in dramatically different conditions.

Also, talk about correlation does not equal causation at your link:

> The basic structure of the Earth, aided by plate tectonics, makes possible the Earth's magnetic field. Neither Venus nor Mars has such a magnetic field. Venus has core and molten regions like the Earth, but a very slow rate of rotation. It produces neither plate tectonics or a magnetic field. Mars has volcanism, but limited to a small number of spectacularly large volcanoes like Olympus Mons. It's magnetic field is weak despite a rotation period similar to that of the Earth. This suggests that the molten nature of the Earth's mantle that facilitates plate tectonics is also essential for the operation of the dynamo that produces the magnetic field.

I mean, N=3 !