Race Origins in Humans

[Fredrico Manuel]

I'm researching the origins of racial differences, and I would
like to base my thesis on molecular biology.  So far, my studies
indicate that there were several reasons for the appearance of 
different races, including genetic mutations and/or drift, natural selection,
adaptations, and many others.  Can anyone tell me if there is evidence
pointing to a specific source?  Thanks!

Mike Ignatoski
University of Michigan