I remember in school we had a new kid that was from a couple of towns over. He would say things like 'straight up.' He probably watched too much tv. If I remember right, he only lasted a few weeks before he left school. Someone told me that he left because he was getting bullied too much. But he seemed to me pretty similar to the other kids.
http://en.wikipedia.org/wiki/Human_skin_color To put it in overly simple terms, present scientific thought is that too much or too little vitamin D is bad. Peoples that have tended to spend too much time in the sun become darker to reduce vitamin D levels absorbed by the skin from the sun, for example equatorial peoples. Peoples that haven't gotten enough sun and therefore vitamin D become lighter so that their bodies will absorb more sunlight. I think there are some holes in this theory, but it's all science has right now. Maybe epigenetics will help.
Image by juan.barredo via FlickrThe "final solution" to vitiligo is to permanently bleach the rest of your skin to that you have even coloring. This isn't inevitable by any means. Many people get one or two spots, and no more for the rest of their lives. Sometimes the spots return to normal color. About 1 in 75 people get vitiligo at some point in their lives.
For more info, google vitiligo. :)