I've seen this map posted in the past and I believe the hypothesis was that the Pop-Soda split grew out of Catholic - Protestant breakdowns. Here in Southeastern Wisconsin the Catholic population is more concentrated along Lake Michigan (all those Germans and Poles) so you get the strip of green along the lake. But I don't remember where I saw that so I can't give a citation.

Would everyone be so up in arms if Watson asserted the Melanin Theory, in which black supremists believe that a greater level of melanin in dark skin "naturally enhances intelligence, emotional sensitivity, and physical prowess." 
 
http://en.wikipedia.org/wiki/Melanin_Theory#Melanin_Theory

Well all of you who think that it is not possible for these two to have a white baby, you are wrong. I have son with a black man and our son has blond hair (with my texture), blue eyes, and white skin. God creates children to be all different kinds.