Re: What are the advantages of different skin colors ?

Gerald:  The skin color cline for human skin color (in other words the 
gradual change in the form or frequency of this trait in space) is not 
generally understood in biological anthropology as directly in terms of 
changes in hot and cold climates.  It is true that a greater degree of 
melanization of the skin occurs in equatorial regions and as we look 
farther north or south there is less melanization of the skin.  However, 
this gradation in skin color is usually understood as involving the 
risk/benefit of ultraviolet radiation vs. intake of vitamin D.  Dark 
colored skin allows for protection from untraviolet radiation and thus 
prevents hypervitaminosis.  Migrating out of the warmer areas, natural 
selection favored a lesser degree of melanization and thus prevented 
rickets (in areas where sun exposure was less).

Dr. Smerken