In Star Wars, basically everyone is a human with facial make-up; is there an attempt at an in-universe explanation of this within this franchise?

Note:formerly this question was for Star Trek and Star Wars, which was too broad. This is now for Star Wars.

Link to old question:
http://scifi.stackexchange.com/questions/14092/do-characters-in-star-trek-address-how-odd-it-is-the-universe-is-filled-with-hum