From my own studies: there is one race -- the human race. The areas of the genetic codes in people which determine their facial and skin features are so tiny as to be almost negligible. Some studies have demonstrated that there are far more genetic differences within 'races' than between them!
Where did these divisions come from? Someone mentioned a great deal of genetic variablity in the first people. That is basically it. When we look at the Table of Nations in Genesis 10, we can see a broad range of 'colors' or pigment levels in each of the three branches of the human race. It is not just the descendants of Ham who are dark! Take a look at the descendants of Japheth, some of whom include the Ethiopians, who are about as black as anyone can be and have distinctly 'white' features.
The son which was being referred to as possibly being dark was Ham, and it had nothing to do with his behavior, for he would have been dark from birth. Some studies in linguistics indicate that his very name "Ham" means 'burnt one.' What is interesting to me is that it is a very short phonetic step from Ham to Herm, which means 'burning one', and there is evidence he may have been the first prototype of the pagan sun god.
As far as Genesis goes, I personally believe that Wiseman was quite correct in his analysis that this book is actually a series of eyewitness accounts, each of which is signed off by the author or authors who wrote. Moses was in a perfect position to take possession of these tablets, which would have been brought down via Noah and then Shem, for he was not only a prince in Egypt but later the leader of the Israelites. There are evidences of editorial comments inserted in a few places, but as he was the one who collated the tablets, they would carry his name, as did the books he actually did write. By the way, the fact that his death is mentioned is simply an addition, probably by Joshua, to formally close Moses' account.
At any rate, back to the original question, the 'races' originated simply due to genetic variation from Adam and Eve. They were most probably of a medium skin tone, which could then be emphasized for darker or de-emphasized for lighter.
If you take a look at how fast we have been able to isolate different characteristics in dogs, thus producing the various breeds, it should be kind of obvious that it doesn't take long for differences to show up.