Human Genetic Diversity

[Jay Mone']

William Tivols response is right on.  Mating between gentically 
diverse populations would certainly increase genetic diversity in the 
offspring of those matings.  However, I'm not sure that in most cases 
it would make any difference in relation to the overall fitness of the 
population.  Take for example, the gene for sickle cell anemia (SCA).  
Homozygous individuals (those who recieve a sickle cell gene from both 
parents) usually suffer serious disease.  This situation is very 
likely if mating occurs between closely-related individual in places 
such as central Africa (bit also occurs in north America), where the 
highest frequency of this allele occurs naturally.  If a homozygous 
individual has access to modern medical care, it is very likely that 
that person will survive long enough to reproduce.  In the Darwinian 
sense, the overall reproductive fitness hasn't really decreased.  Now 
look at a heterozygous individual, who recieves one sickle cell gene 
and one "normal" gene.  This happens frequently in countries such as 
the US, which has significant population diversity.  Such 
heterozygotes don't have disease, but do have an increased resistance 
to malaria.  However, in north America, this resistance has no real 
advantage, and so doesn't make the individual any more fit than 
someone who does not carry the sickle cell gene.
In short, technology has significantly eliminated the fitness question 
in many cases, and so I don't feel it would matter either way.

Jay Mone'