Man evolved in East Africa about 125,000 years ago and, for the first 70,000 years of our existence, virtually all humans were dark-skinned; this trait offered protection from the intense, tropical sun, which characterized their habitat across Africa, southern Asia and Australia. About 50,000 years ago, man began to spread northward, entering temperate regions where solar radiation was reduced by the seasonal change of the sun angle. As has occured in other species, variability in skin pigmentation began to develop among human populations, reflecting an adaptation to the environment via the process of natural selection. Today, a spectrum of skin coloration characterizes our species and further variation will occur due to gene mixing through inter-racial marriages.
Unfortunately, this single human trait, though totally unrelated to other human features and capabilities, has become a rationale for discrimination and persecution. Rooted in ignorance, such beliefs are ingrained in children at a young age and fostered by one's political, cultural and religious environment. Uneducated humans, exposed to the influence of religious fundamentalists and other hate groups, develop racist views; this process is especially common in social groups where science is discredited. By accepting creationism and rejecting evolution, such groups find it easy to buy into the concept of racial distinctions; God surely designed a superior race in his own image!
Hopefully, the election of President Obama will put another nail in the coffin of racism. But until we evolve beyond the ignorance of our ancestors, this ugly mindset will remain a part of human society.