Re: Why do people have less melaninin their skin now than centuries ago?

Dear Shama Khan:

Since humans originated in equatorial latitudes it is a safe bet that all 
humans were at one time dark skinned.  This is because a high level of 
melanin affords protection against the dangerous and damaging affects of 
ultraviolet radiation from the sun.  When some humans moved to more 
northerly latitudes less melanin was advantageous since the levels of  
ultraviolet radiation were much reduced. At the same time the lighter skin 
pigmentation allowed the absorption of vitamin D (necessary in the 
prevention of rickets) in these northern latitudes.  Overall, the 
difference in degree of melanization of human populations has been a result 
of natural selection resulting from biological responses to differences in 
environmental stimuli.

Dr. Smerken