AKSWulfe:Hey! You were watching the news last night too, huh? 
I was painting my roof aluminum last night but I saw much earlier studies of rural/urban children subjected or free from farm animals' company.
Seriously though, I can't believe that was ever in question (about immune systems)... muscles will atrophy if you don't use 'em.
If you don't put the immune system through it's trials and tribulations early on, that would lend itself to being under developed.
...eventually the offspring of two parents who did not develop their immune system will result in a child possibly without an immune system or with a very weak one.... You are very confused here
I have to tell you that citing "scientific" explanation you've heard on the news may make you a target of quite a few laughs.
Here is how it really works - well, closer to reality, in any case.
The issue is not with immune system unneended - despite all the progress the microbes around and populating us (some beneficial) would kill us in minutes it failed. It's that immune system has to face different tasks (many are harder harder) in civilised urban environment that in jungle forest.
Allergy is caused not by atrophied immune system but complete opposite - overreactive immune system - that
supposedly did not get a chance to be "calibrated" during early (intrauterine/early age) development.
At the same time population dencity of urban living make a person much likely to be exposed to all kinds of germs than "uncivilised" life would. Lack of exercise is hardly an issue. The challenges may be different from those geneticallyn programmed. Exellenmt resistance to yellow fewer or malaria (same?) does not help much in New York.
Many birth "defects" come not only from two parents who were unhealthy, but also from very healthy parents. So healthy in fact, that the construction plans for their offspring altered such that the underused/unused body operations weren't fully developed, or developed at all in some extreme cases. I was thinking of that - whether major races diverged far enough for their sets of genes to lose some compatibility. It does not seem to be the case. Hybrids are quite good in most cases. Of course whites-asians are not as diverged as those two groups from blacks and lived in similar "civilised" conditions with constant gene exchange.
Blacks in US do have about 25% of white genes on average though it differs a lot geographically. Could have that negatively affected them? If it did, it would probably be in the most subtle and sophisticated systems.
Of course the immune system is the most sophisticated system in our organism after the brain - likely to be affected by even minor screwup.
Whatever the origins of disparity - evolution or mixing genes, it exists. Unlike brain, well-functioning immune system is necessary for survival in our society. And it's not a career suicide to notice and talk about racial differences with regard to immunity unlike the other kind of differences.
miko
