I think that has to do with his work to try and avoid the Swedish mass surveilance: http://blog.brokep.com/2010/01/09/fra-to-hell/

In TNG there's a plot line to explain why the races in the alpha quadrant are so similar, it's because they all come form the same "DNA-pool" spread out over the different worlds by an ancient race that existed before there were life in that part of the galaxy. I think this plot line was at the end of season 6 and beginning of season 7, but I'm not sure.

And there are energy beeings and others, just watch Enterprise, Voyager or TNG.