As far as the article says about humans changing into something else and not being able to return to Earth, I do find that laughable. If humans are born on other worlds, in galaxies far, far away, and the conditions are similiar to Earth or harsher (higher gravity, lower air density, etc) they could return quite easily and find Earth to be far easier on them. The only problem that might occur is if somehow the species begins to split, where there are people living on planets who's conditions are far lower (significantly less gravity for example) and they try to return, life will be difficult at first. I guess depending on how far apart the conditions are and are much they have changed. But I don't see humans being around long enough for this to happen enough. Besides, I know what's going to happen, I watch movies. Humans go and terraform other planets and create New Earths, so there's no need to worry about conditions different from Earth, aimirite? Or there's always the chance we'll move to a red sun and gain super human like powers. 8)