Whites are just albinos that were kicked outta black society for being, well, 'freaks'. This happened a long time ago. The white freaks ended up in Europe, primarily in Scandinavia. Lotsa blonds. Since they had a closed society, they were able to develop scientific processes. They had some strange off-shoots such as the Roman society and Huns.
Natural selection. A lack of melanin is an advantage in cooler climates, so those who were genetically predisposed to fairer skin lived longer and bred more prolifically. They also had to compete more vigorously for more meagre resources, so came up with more efficient ways of bumping each other off.
