Yes, this is in fact very true. Can be seen in this urban world. Last time my dad used to tell me that when he was young, he used to play in the drains, swim in the stream, catch frogs, play in the field, run bare footed everywhere in the street, drink pipe water etc etc. All in which is perceived unhygienic in this urban society.

I can now see urban parents are over concerned over whether food that they feed their children is sterilize enough, diamond water system in their homes...cannot play bare footed in the field, hygiene of their children is watched closely by their parents.

When children are brought up in such an environment, they will be more vulnerable to harmless disease later on in their lives. For eg. H1N1 fatality rate is low, but yet few percentage of the society die of this disease. Urban society immune system is weakened by its own practice.

In fact evolution or "natural selection" is slowed down by human beings. Natural selection acts by eliminating population that is weak, those that survived are strong population with high resistance and will reproduce to replace those that are dead. But human disturbed this phenomenon by producing medicine, built up facility, laws in which the weak are protected. In short, the natural selection does not take its natural course. The weak still survive and breed in this society and the gene pool still contains those weak individuals....

Indeed, very true. In fact, human themselves are making this life more and more complicated that sooner or later we are destroying ourselves with all the things we created.