The problem there of course is just finding fossils that old. And if they didn't have shells that would make it even more difficult. Soft bodied life forms don't fossilize well. And then there is the question of whether a methane metabolism would have the energy available to create complex life forms. I'm not sure how much energy is required for the development of more complex creatures.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.