If humanity colonized other planets, which planet would be the capitol planet?

In the early stages, Earth would certainly be the dominant planet in any alliance of human worlds. It is possible that some kind of disaster would destroy human civilization on Earth after offworld colonies have been founded, in which case the largest or most powerful or most strategically well placed would become the new capital world. But it is hard to imagine any world settled only by humans being dominant over Earth for the next few thousand years at least... if you ask me.