Re: Are different human races simply sub-species?

Dear 'bocab':

As a biological anthropologist my specialty is human biological variation 
and human biological evolution.  I can tell you that the vast majority of 
present day biologists, especially biological anthropologists, do not 
believe that 'race' is a useful concept when applied to humans.  Rather, 
the concept of 'cline' has been the cornerstone in the explanation of 
modern human variation.  A cline can be understood as  the gradual change 
in the form or frequency of a trait over space.  For example, 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.  Simply 
put, this gradation has to do with the environmental risk/benefit of 
ultraviolet radiation vs. intake of vitamin D.  There is some controversy 
over the length of time associated with the biological variation we see 
between modern humans.  While some would argue for 200,000 years others see 
this variation as very possibly occurring within the last 10,000 to 30,000 
years.  Modern humans are very close genetically and in fact there are 
greater genetic differences within geographical human groups than between 
them.

Dr. Smerken