MadSci Network: Evolution

Re: Why did seperate races evolve in humans?

Date: Wed Sep 15 12:30:41 1999
Posted By: Dr. David Smerken, retired Ph.D., BIOANTHROPOLOGY, DNA.
Area of science: Evolution
ID: 936999605.Ev

Dear questioner:

First of all, most modern day biological anthropologists do not find that 
the concept of 'race' is useful when applied to humans.  Human biological 
variation is better viewed in terms of 'clines,' in other words gradual 
changes in the frequency of specific traits over space.  You are right that 
humans were basically one skin color (darkly pigmented) when they all lived 
in equatorial Africa.  Within the past several hundred thousand years, as 
humans spread out to the north and south of the equator this particular 
phenotypical trait can be seen in terms of a gradual gradient reflecting 
lighter skin color the further north or south from the equator that humans 
settled.  This gradation in skin color is usually understood as involving 
the risk/benefit of ultraviolet radiation vs. intake of vitamin D.  
Biological Anthropologists have found many clines for numerous human 
biological traits some fairly simple and others very complicated.  I 
recommend for further reading that you take a look at Stephen Jay Gould's 
book "The Mismeasure of Man" and a good textbook of biological anthropology 
such as Weiss and Mann's "Human Biology and Behavior."

Dr. Smerken

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