white people weren't around 50,000 years ago. Roughly 6000 years ago is when they appeared. A couple of articles that support my claim.
One Common Ancestor Behind Blue Eyes | LiveScience
http://galsatia.files.wordpress.com/2007/04/blanche_paleur.pdf
6000 years ago is about 4000 bc. Not to long after that all of the ancient "modern" civilizations were being invaded by outsiders. Menes had to reunite egypt, hyksos caused trouble around 1700 bc, aryans invaded India, hitties, invaders of china etc.
Adam of the bible is 6000 years old but as we know he's not the 1st person on the planet...
Being a mutation of the original people, something genetically had to have happen to change the color. As I like to say, god didn't make white because it looked good. Everything happens for a reason. I've mentioned slc24a5, but melanin is also a factor here of course.
Elijah Muhammad said in the black man there exist 2 germs, a black one and a brown one(eumelanin). Someone above posted a yacub video, well with those who know the story(read message to the blackman, not wikipedia or some other outside source), he had a birth control process(can be found in the bible)which included separating the brown germ from the black germ and destroying the black germ. After following that process for a period of time the germ became white.
This can be shown & proven by taking a dark black person and a person of a lighter shade and having them produce a child. This child grows up and has a kid with a partner of lighter complexion than him/her and repeat. Or simply take a black and white person to reduce the grafting time.